Mysterious No Start - Magically Starts Issue

airline tech

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I wanted to dig into the occasional mystery of electrical issues and no start events, so being inquisitive I dug deep into the wiring diagrams and operation information on the Ranger.

Keep in mind that the wiring manuals are designed to follow power paths with key on and powered, so this made a challenge in trying to find the problem area when this event happens. (No-Power and No-Start)

My initial thoughts on this were the PCM Power Relay sticking, but concluded although related it is not the issue.
Note: I attempted to play some with the truck and force it into a failure mode by pulling fuses and relays to try to locate the circuit causing the issue. But realized that the BJB (Battery Junction Box) was a PITA to get access to the lower side of the box (High Power-Fuses) and pulling a relay out was difficult as well.
So, I scrapped the idea as it was not worth breaking something just to prove a theory.

So here are some operation notes for the truck - Copy & Paste for relevant info.

BCM Control (Timers) for Lighting and Related -- Pay attention to the (Timed-Function)

Headlamp Exit Delay

After you switch the ignition off, you can switch the headlamps on by pulling the direction indicator lever toward you. You will hear a short tone. The headlamps will switch off automatically after three minutes with any door open or 30 seconds after the last door has been closed. You can cancel this feature by pulling the direction indicator toward you again or switching the ignition on.

Battery Saver

NOTE:
Time-out is 10 seconds if the vehicle is in factory mode or 1 minute if the vehicle is in transport mode.

The BCM provides automatic shut-off of the courtesy and demand lamps after a time-out period when the ignition is OFF. A timer in the BCM starts when:

  • the ignition transitions to OFF.
  • the front or rear interior lamp was switched ON.
  • any door becomes ajar.
  • any button of a RKE transmitter is pressed.
  • a door is unlocked using the passive entry feature.
  • a valid code was entered on the keyless entry keypad.
When 10 minutes (30 minutes for demand lamps) have elapsed, the BCM automatically shuts off voltage to the lamps. The timer restarts (voltage is restored if the BCM is in battery saver mode) when:

  • the ignition transitions out of OFF.
  • the front or rear interior lamp was switched ON.
  • any door becomes ajar.
  • any button of a RKE transmitter is pressed.
  • a door is unlocked using the passive entry feature.


1694706562940.png


Normal Operation: Basic's

If we look at the very bottom of this diagram, you will see highlighted circuit, this circuit s controlled by the BCM and is a micro controlled circuit with a relay within the BCM (Non-Serviceable)

The FET (Field Effect Transistor) This is internal circuit protection for (INDIVUDUAL) lighting circuits and cuts power and disables the circuit if a short is detected.
I do not believe this is an issue in this case, this is just a input monitor for this circuit.

PCM - WAKE - (Explained)
The wake-up control circuit wakes up the PCM prior to the engine cranking. The PCM needs to wake up prior to a crank request so it has time to go through its initialization. The wake-up control circuit is controlled by the BCM . The BCM activates the wake-up control circuit when the driver door is opened, the BCM detects a passive key, or when the engine start/stop button is pressed.

(You can see the (BSI) above work for this wake, if you sit in the truck either in Assy or Off, press brake pedal and you can hear the Wastegate Actuator cycle.
BSI=Brake Shift Interlock, so brake pedal input will wake it as well
Note: After 3-Minutes the PCM Relay deenergizes, if you press the brake pedal it wakes back up and reenergizes.

Lock and Unlock Doors - The trigger on feedback lights (flash) - DRL's,, Park - Taillights Etc.

Open the door - Door Ajar switch, which is grounded when closed, - (Now Open - Circuit), this open circuit triggers the micro control and the courtesy (interior) lighting circuit has been powered, plus a ground has been supplied to the control side of the PCM Power Relay.

When the PCM Power Relay is energized, you hear the (NOISY) Waste Gate Actuator move into position for engine start plus the Fuel Pump Relay is energized for 3 seconds to purge fuel vapor from the HPFP.

Note: If there is no engine start within (3-Minutes) then the PCM Power Relay, will deenergize.

Other noted timed events that come into play for this event:

When engine is shut off, you have Accerary Power for (10-Minutes) or until door is opened or engine is restarted.

Headlamp Exit Delay

When the ignition is OFF and the LH multifunction switch is placed in the flash-to-pass position and released, the parking lamps and low beams are illuminated. They remain illuminated until:
  • 3 minutes have elapsed with a door open.
  • 30 seconds have elapsed after all doors are closed.
  • the LH multifunction switch is placed in the flash-to-pass position again.
  • the ignition switches to RUN.
Within the 30 second delay and all the doors closed, opening any door results in the 3 minute timer restarting.


My thought on what is actually happening - With no power to door locks, lights or ignition switch.

So on paper here and what I see in this Wake circuit is that when in Demand LP / Batt Save, which involves 3-circuits.
PATS, Door Locks/Entry, and Interior / exterior lighting.

The interior illumination and door lock circuit includes (Pull-Down) resistors, as with interior lights they dim down to off.

This circuit is not waking up - it wakes by seeing a power draw on the circuit from any of the monitored circuits.
and if I am correct the issue would be the internal (micro control) of the BCM sticking and (NOT) allowing the circuit to wake
Basically, it is a current sense (controller)

So, the RTM Module and PATS Receiver and TCU are working and transmitting as they have power. (I believe) to remote lock/unlock, start etc.
but the wake-up response circuit is still asleep.
The reason for no response with FOB or Ford Pass and being at the truck manually trying to enter through the doors. Use your (key blade) to open door (mechanically), unlock door and open door still no wake signal. (No-Power), try to start, No-Power (Due to no wake signal)


THE RESET PROCEDURE - That appears to work - (The Back Door Way)

Now, before you panic and think I need a jump, we appear to be able to reset the system by providing a back door (knock) to wake this circuit.

With previous posters stating that just wait a few minutes up to 10 minutes and it starts like nothing happened.
I dug some into the manuals looking for timed events. and noted that there was full battery power (Just Hidden)

Now exactly what timed event (Above) is providing the reset (IDK) (GUESSING-HERE) but it appears to reset the circuit.

But think that when you try to start (Failed), you are powering the Run/Start Relay but not the Starter Relay as the PCM has no wake-up voltage.
This is HIDDEN voltage and you have cycled the ignition switch from off to start and back to off, this powering the Accessary Relay (Delay) 10-Minute Timer
you have also provided a cycle to the PCM Relay (3-Minute) Timer and the Headlamp Exit Delay Timer (3-Minutes)

So, somehow a cycle of the ignition switch gets power on the wake-up circuit and resets it and all is normal like nothing happened.
My thought is the (Headlamp Exit Relay-Delay) Timer might be the highlight of the event of a reset.

Some thoughts would be since IDK, would be what if you (possibles) when in this failure state.
as a quicker fix (vs waiting on a timed event) just some ideas to try here.

1. Try turning on the (Courtesy) light - Force Power on the circuit, instead of door ajar control.
2. Try turning on the Park and or Headlights - Force Power on the circuit, instead of Autolamp control and or entry/ exit response and door lock feedback response.
3. Sound the Horn, force power on the door lock control circuit, as the horn sounds if you double lock the truck from the FOB.



Update and Edit:

I found the Backdoor - Wake for the PCM

If we take the Ignition switch to start and back to on /run- we provide the ground to energize the Run/Start Relay - This is (H) Input on the diagram - (Above) (Hidden Voltage)

With the Run/Start Relay now allowing power - we get power on (Fuse 28), this provides the voltage to the PCM (Pin 64) (Above) (Hidden Voltage)

This is the Ignition State Input to the PCM, Power flow to the PCM allows for the Ground to be applied to the PCM Power Relay (Backdoor) Wake (on the wake circuit)


See diagram below:

PCMRC = PCM Relay Control

This power transition (By-Passing) The Wake Control, sets the 3-Minute Timer for the PCM Power Relay.
So, at this point, you still do not have power to all the circuits, you still have the wake side still asleep -at the BCM Pin 18 (Below)
The PCM has power, but the BCM still has not provided the primary wake signal (Pin 18 to Pin 52).

This is where the 3-Minute Timer sets (If an engine start is not completed within the 3-Minutes the PCM Power relay (Deenergizes) by removing the ground signal from the relay (Pin 25-PCMRC)
and
During this (3-Minutes) of power you are powering the Accessary Relay (Delay)
which has a (10-Minute) Timer for power, after 10-minutes with door remaining closed, it will shut down, if a door is opened, it shuts down when door is opened.

So, here are the important timed event counters that come into play and explains why owners who have posted the No-Start issue, experience different outcomes.
And it depends on whether you have open and closed the driver's door.

Note: The Accessary Relay Delay is when you shut off the truck and listen to music, if you just sit and do not open the door it stays on for 10-Minutes

Anyway, this power cycle on the circuits appears to work, I have not had it happen to me (yet) but I had to find an answer to the mystery.
Why does it happen? IDK, a Low Battery voltage might come into play here, but we know it's on that wake-up circuit - The Circuit is not getting the BCM (Nudge) to Tap the PCM on the shoulder and tell it to wake.

Since this appears to be a rare occurrence, and (One Time) events, I don't see anything other than a small little micro that was being lazy and wanted more nap time. (BCM - PCM Wakeup)

1694769102884.png


So, for clarification with diagram in view

Pin 18 to Pin 52 = Wake Up signal from BCM Primary (Lazy Circuit) that is killing all power to Lights etc.

Run Start Relay - Secondary Power, From Key Cycle - Powers the PCM (ISP-R) Pin 64

Pin 64 - Allows / Triggers the Ground to the PCM Power Relay (PCM - Pin 25)

Normal Operation = Wake Signal powers, allowing TCU, RTM, Door Locks, Lights Etc to Power.

When door is opened - the Door Ajar switch triggers Courtesy / Dome light on, this action does the same event as above, PCM Power Relay will energize for 3-Minutes, this is the Noisy Wastegate and FP Purge of vapor.
When the engine is started the Run/Start Relay - (Being Energized) keeps the PCM Power Relay Energized, so the 3-Minute Timer is not in play.
Sponsored

 
Last edited:
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airline tech

airline tech

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I updated the post with a more detailed decription
 

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Yeah , i was coming up with the same things , if i didn't know better , i would accuse you of looking at my notes ...
 

subquark

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I wanted to dig into the occasional mystery of electrical issues and no start events, so being inquisitive I dug deep into the wiring diagrams and operation information on the Ranger.

Keep in mind that the wiring manuals are designed to follow power paths with key on and powered, so this made a challenge in trying to find the problem area when this event happens. (No-Power and No-Start)

My initial thoughts on this were the PCM Power Relay sticking, but concluded although related it is not the issue.
Note: I attempted to play some with the truck and force it into a failure mode by pulling fuses and relays to try to locate the circuit causing the issue. But realized that the BJB (Battery Junction Box) was a PITA to get access to the lower side of the box (High Power-Fuses) and pulling a relay out was difficult as well.
So, I scrapped the idea as it was not worth breaking something just to prove a theory.

So here are some operation notes for the truck - Copy & Paste for relevant info.

BCM Control (Timers) for Lighting and Related -- Pay attention to the (Timed-Function)

Headlamp Exit Delay

After you switch the ignition off, you can switch the headlamps on by pulling the direction indicator lever toward you. You will hear a short tone. The headlamps will switch off automatically after three minutes with any door open or 30 seconds after the last door has been closed. You can cancel this feature by pulling the direction indicator toward you again or switching the ignition on.

Battery Saver

NOTE:
Time-out is 10 seconds if the vehicle is in factory mode or 1 minute if the vehicle is in transport mode.

The BCM provides automatic shut-off of the courtesy and demand lamps after a time-out period when the ignition is OFF. A timer in the BCM starts when:

  • the ignition transitions to OFF.
  • the front or rear interior lamp was switched ON.
  • any door becomes ajar.
  • any button of a RKE transmitter is pressed.
  • a door is unlocked using the passive entry feature.
  • a valid code was entered on the keyless entry keypad.
When 10 minutes (30 minutes for demand lamps) have elapsed, the BCM automatically shuts off voltage to the lamps. The timer restarts (voltage is restored if the BCM is in battery saver mode) when:

  • the ignition transitions out of OFF.
  • the front or rear interior lamp was switched ON.
  • any door becomes ajar.
  • any button of a RKE transmitter is pressed.
  • a door is unlocked using the passive entry feature.


1694706562940.png


Normal Operation: Basic's

If we look at the very bottom of this diagram, you will see highlighted circuit, this circuit s controlled by the BCM and is a micro controlled circuit with a relay within the BCM (Non-Serviceable)

The FET (Field Effect Transistor) This is internal circuit protection for (INDIVUDUAL) lighting circuits and cuts power and disables the circuit if a short is detected.
I do not believe this is an issue in this case, this is just a input monitor for this circuit.

PCM - WAKE - (Explained)
The wake-up control circuit wakes up the PCM prior to the engine cranking. The PCM needs to wake up prior to a crank request so it has time to go through its initialization. The wake-up control circuit is controlled by the BCM . The BCM activates the wake-up control circuit when the driver door is opened, the BCM detects a passive key, or when the engine start/stop button is pressed.

(You can see the (BSI) above work for this wake, if you sit in the truck either in Assy or Off, press brake pedal and you can hear the Wastegate Actuator cycle.
BSI=Brake Shift Interlock, so brake pedal input will wake it as well
Note: After 3-Minutes the PCM Relay deenergizes, if you press the brake pedal it wakes back up and reenergizes.

Lock and Unlock Doors - The trigger on feedback lights (flash) - DRL's,, Park - Taillights Etc.

Open the door - Door Ajar switch, which is grounded when closed, - (Now Open - Circuit), this open circuit triggers the micro control and the courtesy (interior) lighting circuit has been powered, plus a ground has been supplied to the control side of the PCM Power Relay.

When the PCM Power Relay is energized, you hear the (NOISY) Waste Gate Actuator move into position for engine start plus the Fuel Pump Relay is energized for 3 seconds to purge fuel vapor from the HPFP.

Note: If there is no engine start within (3-Minutes) then the PCM Power Relay, will deenergize.

Other noted timed events that come into play for this event:

When engine is shut off, you have Accerary Power for (10-Minutes) or until door is opened or engine is restarted.

Headlamp Exit Delay

When the ignition is OFF and the LH multifunction switch is placed in the flash-to-pass position and released, the parking lamps and low beams are illuminated. They remain illuminated until:
  • 3 minutes have elapsed with a door open.
  • 30 seconds have elapsed after all doors are closed.
  • the LH multifunction switch is placed in the flash-to-pass position again.
  • the ignition switches to RUN.
Within the 30 second delay and all the doors closed, opening any door results in the 3 minute timer restarting.


My thought on what is actually happening - With no power to door locks, lights or ignition switch.

So on paper here and what I see in this Wake circuit is that when in Demand LP / Batt Save, which involves 3-circuits.
PATS, Door Locks/Entry, and Interior / exterior lighting.

The interior illumination and door lock circuit includes (Pull-Down) resistors, as with interior lights they dim down to off.

This circuit is not waking up - it wakes by seeing a power draw on the circuit from any of the monitored circuits.
and if I am correct the issue would be the internal (micro control) of the BCM sticking and (NOT) allowing the circuit to wake
Basically, it is a current sense (controller)

So, the RTM Module and PATS Receiver and TCU are working and transmitting as they have power. (I believe) to remote lock/unlock, start etc.
but the wake-up response circuit is still asleep.
The reason for no response with FOB or Ford Pass and being at the truck manually trying to enter through the doors. Use your (key blade) to open door (mechanically), unlock door and open door still no wake signal. (No-Power), try to start, No-Power (Due to no wake signal)


THE RESET PROCEDURE - That appears to work - (The Back Door Way)

Now, before you panic and think I need a jump, we appear to be able to reset the system by providing a back door (knock) to wake this circuit.

With previous posters stating that just wait a few minutes up to 10 minutes and it starts like nothing happened.
I dug some into the manuals looking for timed events. and noted that there was full battery power (Just Hidden)

Now exactly what timed event (Above) is providing the reset (IDK) (GUESSING-HERE) but it appears to reset the circuit.

But think that when you try to start (Failed), you are powering the Run/Start Relay but not the Starter Relay as the PCM has no wake-up voltage.
This is HIDDEN voltage and you have cycled the ignition switch from off to start and back to off, this powering the Accessary Relay (Delay) 10-Minute Timer
you have also provided a cycle to the PCM Relay (3-Minute) Timer and the Headlamp Exit Delay Timer (3-Minutes)

So, somehow a cycle of the ignition switch gets power on the wake-up circuit and resets it and all is normal like nothing happened.
My thought is the (Headlamp Exit Relay-Delay) Timer might be the highlight of the event of a reset.

Some thoughts would be since IDK, would be what if you (possibles) when in this failure state.
as a quicker fix (vs waiting on a timed event) just some ideas to try here.

1. Try turning on the (Courtesy) light - Force Power on the circuit, instead of door ajar control.
2. Try turning on the Park and or Headlights - Force Power on the circuit, instead of Autolamp control and or entry/ exit response and door lock feedback response.
3. Sound the Horn, force power on the door lock control circuit, as the horn sounds if you double lock the truck from the FOB.



Update and Edit:

I found the Backdoor - Wake for the PCM

If we take the Ignition switch to start and back to on /run- we provide the ground to energize the Run/Start Relay - This is (H) Input on the diagram - (Above) (Hidden Voltage)

With the Run/Start Relay now allowing power - we get power on (Fuse 28), this provides the voltage to the PCM (Pin 64) (Above) (Hidden Voltage)

This is the Ignition State Input to the PCM, Power flow to the PCM allows for the Ground to be applied to the PCM Power Relay (Backdoor) Wake (on the wake circuit)


See diagram below:

PCMRC = PCM Relay Control

This power transition (By-Passing) The Wake Control, sets the 3-Minute Timer for the PCM Power Relay.
So, at this point, you still do not have power to all the circuits, you still have the wake side still asleep -at the BCM Pin 18 (Below)
The PCM has power, but the BCM still has not provided the primary wake signal (Pin 18 to Pin 52).

This is where the 3-Minute Timer sets (If an engine start is not completed within the 3-Minutes the PCM Power relay (Deenergizes) by removing the ground signal from the relay (Pin 25-PCMRC)
and
During this (3-Minutes) of power you are powering the Accessary Relay (Delay)
which has a (10-Minute) Timer for power, after 10-minutes with door remaining closed, it will shut down, if a door is opened, it shuts down when door is opened.

So, here are the important timed event counters that come into play and explains why owners who have posted the No-Start issue, experience different outcomes.
And it depends on whether you have open and closed the driver's door.

Note: The Accessary Relay Delay is when you shut off the truck and listen to music, if you just sit and do not open the door it stays on for 10-Minutes

Anyway, this power cycle on the circuits appears to work, I have not had it happen to me (yet) but I had to find an answer to the mystery.
Why does it happen? IDK, a Low Battery voltage might come into play here, but we know it's on that wake-up circuit - The Circuit is not getting the BCM (Nudge) to Tap the PCM on the shoulder and tell it to wake.

Since this appears to be a rare occurrence, and (One Time) events, I don't see anything other than a small little micro that was being lazy and wanted more nap time. (BCM - PCM Wakeup)

1694769102884.png


So, for clarification with diagram in view

Pin 18 to Pin 52 = Wake Up signal from BCM Primary (Lazy Circuit) that is killing all power to Lights etc.

Run Start Relay - Secondary Power, From Key Cycle - Powers the PCM (ISP-R) Pin 64

Pin 64 - Allows / Triggers the Ground to the PCM Power Relay (PCM - Pin 25)

Normal Operation = Wake Signal powers, allowing TCU, RTM, Door Locks, Lights Etc to Power.

When door is opened - the Door Ajar switch triggers Courtesy / Dome light on, this action does the same event as above, PCM Power Relay will energize for 3-Minutes, this is the Noisy Wastegate and FP Purge of vapor.
When the engine is started the Run/Start Relay - (Being Energized) keeps the PCM Power Relay Energized, so the 3-Minute Timer is not in play.
Wow! I read every single word and find your post fascinating and very helpful.

This gives me more confidence in, what to me, seems like such a complex system (keep in mind my only mechanical expertise is with a '72 Land Cruiser that I fully understand and am confident I can fix anything - lol, prior to that was a '60 MGA that I did a frame up restoration on and it's fanciness was pneumatic turn signal and an oil gauge with a tube direct from the engine!).

I had this mystery "no start" event once in a grocery store parking lot. I used the remote open but the tailgate stayed locked. Went to the driver door and it wouldn't unlock upon a few more fob presses. Unlocked the door with the key and tried to start the truck with the key at least twice, nada. Unlocked the tailgate with the door's unlock button and loaded up my groceries, and closed the tailgate. Put cart in cart corral, and then back to start the truck. Got it, put the key in, and ta da! What a relief!

So your write up gives me confidence that it wasn't a fail per se, just one of the things you discussed.

As far as any Ranger expertise I have, I'm happy that I was able to turn off the driver seat belt minder! I live in NH where we can legally be violently ejected from the windshield if we choose not to belt up.

Thanks again! =)

MGA turn signal switch
1694784313129.jpeg
 

34TL34D

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I wanted to dig into the occasional mystery of electrical issues and no start events, so being inquisitive I dug deep into the wiring diagrams and operation information on the Ranger.

Keep in mind that the wiring manuals are designed to follow power paths with key on and powered, so this made a challenge in trying to find the problem area when this event happens. (No-Power and No-Start)

My initial thoughts on this were the PCM Power Relay sticking, but concluded although related it is not the issue.
Note: I attempted to play some with the truck and force it into a failure mode by pulling fuses and relays to try to locate the circuit causing the issue. But realized that the BJB (Battery Junction Box) was a PITA to get access to the lower side of the box (High Power-Fuses) and pulling a relay out was difficult as well.
So, I scrapped the idea as it was not worth breaking something just to prove a theory.

So here are some operation notes for the truck - Copy & Paste for relevant info.

BCM Control (Timers) for Lighting and Related -- Pay attention to the (Timed-Function)

Headlamp Exit Delay

After you switch the ignition off, you can switch the headlamps on by pulling the direction indicator lever toward you. You will hear a short tone. The headlamps will switch off automatically after three minutes with any door open or 30 seconds after the last door has been closed. You can cancel this feature by pulling the direction indicator toward you again or switching the ignition on.

Battery Saver

NOTE:
Time-out is 10 seconds if the vehicle is in factory mode or 1 minute if the vehicle is in transport mode.

The BCM provides automatic shut-off of the courtesy and demand lamps after a time-out period when the ignition is OFF. A timer in the BCM starts when:

  • the ignition transitions to OFF.
  • the front or rear interior lamp was switched ON.
  • any door becomes ajar.
  • any button of a RKE transmitter is pressed.
  • a door is unlocked using the passive entry feature.
  • a valid code was entered on the keyless entry keypad.
When 10 minutes (30 minutes for demand lamps) have elapsed, the BCM automatically shuts off voltage to the lamps. The timer restarts (voltage is restored if the BCM is in battery saver mode) when:

  • the ignition transitions out of OFF.
  • the front or rear interior lamp was switched ON.
  • any door becomes ajar.
  • any button of a RKE transmitter is pressed.
  • a door is unlocked using the passive entry feature.


1694706562940.png


Normal Operation: Basic's

If we look at the very bottom of this diagram, you will see highlighted circuit, this circuit s controlled by the BCM and is a micro controlled circuit with a relay within the BCM (Non-Serviceable)

The FET (Field Effect Transistor) This is internal circuit protection for (INDIVUDUAL) lighting circuits and cuts power and disables the circuit if a short is detected.
I do not believe this is an issue in this case, this is just a input monitor for this circuit.

PCM - WAKE - (Explained)
The wake-up control circuit wakes up the PCM prior to the engine cranking. The PCM needs to wake up prior to a crank request so it has time to go through its initialization. The wake-up control circuit is controlled by the BCM . The BCM activates the wake-up control circuit when the driver door is opened, the BCM detects a passive key, or when the engine start/stop button is pressed.

(You can see the (BSI) above work for this wake, if you sit in the truck either in Assy or Off, press brake pedal and you can hear the Wastegate Actuator cycle.
BSI=Brake Shift Interlock, so brake pedal input will wake it as well
Note: After 3-Minutes the PCM Relay deenergizes, if you press the brake pedal it wakes back up and reenergizes.

Lock and Unlock Doors - The trigger on feedback lights (flash) - DRL's,, Park - Taillights Etc.

Open the door - Door Ajar switch, which is grounded when closed, - (Now Open - Circuit), this open circuit triggers the micro control and the courtesy (interior) lighting circuit has been powered, plus a ground has been supplied to the control side of the PCM Power Relay.

When the PCM Power Relay is energized, you hear the (NOISY) Waste Gate Actuator move into position for engine start plus the Fuel Pump Relay is energized for 3 seconds to purge fuel vapor from the HPFP.

Note: If there is no engine start within (3-Minutes) then the PCM Power Relay, will deenergize.

Other noted timed events that come into play for this event:

When engine is shut off, you have Accerary Power for (10-Minutes) or until door is opened or engine is restarted.

Headlamp Exit Delay

When the ignition is OFF and the LH multifunction switch is placed in the flash-to-pass position and released, the parking lamps and low beams are illuminated. They remain illuminated until:
  • 3 minutes have elapsed with a door open.
  • 30 seconds have elapsed after all doors are closed.
  • the LH multifunction switch is placed in the flash-to-pass position again.
  • the ignition switches to RUN.
Within the 30 second delay and all the doors closed, opening any door results in the 3 minute timer restarting.


My thought on what is actually happening - With no power to door locks, lights or ignition switch.

So on paper here and what I see in this Wake circuit is that when in Demand LP / Batt Save, which involves 3-circuits.
PATS, Door Locks/Entry, and Interior / exterior lighting.

The interior illumination and door lock circuit includes (Pull-Down) resistors, as with interior lights they dim down to off.

This circuit is not waking up - it wakes by seeing a power draw on the circuit from any of the monitored circuits.
and if I am correct the issue would be the internal (micro control) of the BCM sticking and (NOT) allowing the circuit to wake
Basically, it is a current sense (controller)

So, the RTM Module and PATS Receiver and TCU are working and transmitting as they have power. (I believe) to remote lock/unlock, start etc.
but the wake-up response circuit is still asleep.
The reason for no response with FOB or Ford Pass and being at the truck manually trying to enter through the doors. Use your (key blade) to open door (mechanically), unlock door and open door still no wake signal. (No-Power), try to start, No-Power (Due to no wake signal)


THE RESET PROCEDURE - That appears to work - (The Back Door Way)

Now, before you panic and think I need a jump, we appear to be able to reset the system by providing a back door (knock) to wake this circuit.

With previous posters stating that just wait a few minutes up to 10 minutes and it starts like nothing happened.
I dug some into the manuals looking for timed events. and noted that there was full battery power (Just Hidden)

Now exactly what timed event (Above) is providing the reset (IDK) (GUESSING-HERE) but it appears to reset the circuit.

But think that when you try to start (Failed), you are powering the Run/Start Relay but not the Starter Relay as the PCM has no wake-up voltage.
This is HIDDEN voltage and you have cycled the ignition switch from off to start and back to off, this powering the Accessary Relay (Delay) 10-Minute Timer
you have also provided a cycle to the PCM Relay (3-Minute) Timer and the Headlamp Exit Delay Timer (3-Minutes)

So, somehow a cycle of the ignition switch gets power on the wake-up circuit and resets it and all is normal like nothing happened.
My thought is the (Headlamp Exit Relay-Delay) Timer might be the highlight of the event of a reset.

Some thoughts would be since IDK, would be what if you (possibles) when in this failure state.
as a quicker fix (vs waiting on a timed event) just some ideas to try here.

1. Try turning on the (Courtesy) light - Force Power on the circuit, instead of door ajar control.
2. Try turning on the Park and or Headlights - Force Power on the circuit, instead of Autolamp control and or entry/ exit response and door lock feedback response.
3. Sound the Horn, force power on the door lock control circuit, as the horn sounds if you double lock the truck from the FOB.



Update and Edit:

I found the Backdoor - Wake for the PCM

If we take the Ignition switch to start and back to on /run- we provide the ground to energize the Run/Start Relay - This is (H) Input on the diagram - (Above) (Hidden Voltage)

With the Run/Start Relay now allowing power - we get power on (Fuse 28), this provides the voltage to the PCM (Pin 64) (Above) (Hidden Voltage)

This is the Ignition State Input to the PCM, Power flow to the PCM allows for the Ground to be applied to the PCM Power Relay (Backdoor) Wake (on the wake circuit)


See diagram below:

PCMRC = PCM Relay Control

This power transition (By-Passing) The Wake Control, sets the 3-Minute Timer for the PCM Power Relay.
So, at this point, you still do not have power to all the circuits, you still have the wake side still asleep -at the BCM Pin 18 (Below)
The PCM has power, but the BCM still has not provided the primary wake signal (Pin 18 to Pin 52).

This is where the 3-Minute Timer sets (If an engine start is not completed within the 3-Minutes the PCM Power relay (Deenergizes) by removing the ground signal from the relay (Pin 25-PCMRC)
and
During this (3-Minutes) of power you are powering the Accessary Relay (Delay)
which has a (10-Minute) Timer for power, after 10-minutes with door remaining closed, it will shut down, if a door is opened, it shuts down when door is opened.

So, here are the important timed event counters that come into play and explains why owners who have posted the No-Start issue, experience different outcomes.
And it depends on whether you have open and closed the driver's door.

Note: The Accessary Relay Delay is when you shut off the truck and listen to music, if you just sit and do not open the door it stays on for 10-Minutes

Anyway, this power cycle on the circuits appears to work, I have not had it happen to me (yet) but I had to find an answer to the mystery.
Why does it happen? IDK, a Low Battery voltage might come into play here, but we know it's on that wake-up circuit - The Circuit is not getting the BCM (Nudge) to Tap the PCM on the shoulder and tell it to wake.

Since this appears to be a rare occurrence, and (One Time) events, I don't see anything other than a small little micro that was being lazy and wanted more nap time. (BCM - PCM Wakeup)

1694769102884.png


So, for clarification with diagram in view

Pin 18 to Pin 52 = Wake Up signal from BCM Primary (Lazy Circuit) that is killing all power to Lights etc.

Run Start Relay - Secondary Power, From Key Cycle - Powers the PCM (ISP-R) Pin 64

Pin 64 - Allows / Triggers the Ground to the PCM Power Relay (PCM - Pin 25)

Normal Operation = Wake Signal powers, allowing TCU, RTM, Door Locks, Lights Etc to Power.

When door is opened - the Door Ajar switch triggers Courtesy / Dome light on, this action does the same event as above, PCM Power Relay will energize for 3-Minutes, this is the Noisy Wastegate and FP Purge of vapor.
When the engine is started the Run/Start Relay - (Being Energized) keeps the PCM Power Relay Energized, so the 3-Minute Timer is not in play.
TLDR
It happened to me with my new 23 xlt. Brand new at about 1500 miles. I think it was a software issue.
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