airline tech
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- Aug 24, 2022
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- Midwest - KS
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- 2022 Ranger Lariat-Super Crew, Cactus Gray
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- Aircraft Tech
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- #1
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:
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:
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)
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.
EDIT: UPDATE 10/22/24
I have done some more digging and noted after looking into an Aftermarket Remote Start Issue.
I think I have found the most likely culprit for the Door Unlock Issues & Starting Issues as well as Courtesy Lighting not coming on when the door is opened.
This is the MAIN & PRIMARY (Micro- Controlled Relay) that MUST close for the BCM to Wake and allow Door Locks, Starting, Courtesy Lighting Etc to function.
This (Micro-Controller) Relay ties into all issues - It is internal to the BCM
This Micro is on the HS 1 Can Network and it is a very important controller as this is the primary thing that needs to close when a request is sent via FOB -Door Lock/Unlock - Remote Start, Wake Door Open, Start Request (Key/PB)
Door Unlock Request (FOB) - RTM is receiving the request and sending the request signal to the BCM via (LIN) the BCM is taking that request and triggers that Micro to close.
Now be it Lazy Relay or Low Voltage as the (BCM- Monitoring) Low State of Charge & Load Shed Request are on this HS-Can 1 circuit.
I am thinking it is just (LAZY) once in a while.
So now you manually unlock the door and get in and attempt to start (Nothing - Dead)
You have now - activated 2 timers in the BCM, one is the 3-Minute Timer for the PCM Power Relay, and the other is the 10-Minute Accessory Delay Timer.
The 3-Minute Timer (Normal Ops) will open the PCM Power Relay (If it does not see an engine start) in those 3-Minutes.
The 10-Minute Timer will open - when either 10-Minutes has elapsed, or a door is opened.
Remote Start (Ford Pass) uses the TCU - but communicates to the GWM - Via HS-Can 4, which then communicates that request to HS-Can 1, which triggers that (Micro) relay in the BCM.
So basically, no matter what you do, which avenue you use to enter or start the truck it takes this Micro-Control (Relay) to close.
The reason for it to magically start working is the Power Cycle across it and I think it has to do with the 3-Minute Timer (providing an internal reset) as well as the 10-Minute Timer.
It is this or the BMS has triggered a Load Shed (Reading a low SOC) and the power cycling in the BCM reactivates what it is load shedding - or just simply a Low Battery Voltage (At Wake)
Edit: 1/21/25
I wanted to update and highlight exactly what this (Micro) does and how it relates to the issues.
This is the (BCM) controller for the send & receive of all (HS1-Can) bus data.
So, if the BCM cannot send or receive the data then the bus is dead.
There is a lot of data that is transmitted on that bus but for this specific issue the following are specific to this issue.
This Data originates from the BCM
1. Door Ajar - This is important as this triggers the PCM wake
2. Vech Lock Status - Door Unlock / Lock status
3. RKE Data - This is the BCM authorizing the FOB functions
4. Accessory Delay (Relay) (The 10-Minute) Timed Relay - That I suspect may be sticking
5. Ign Status - So Ignition Switch Position or ISP-R (Run)
6. PATS Control Command
7. Batt Low SOC
8. Load Shed Req
9. Power Shed Level
So exactly what specific is not allowing the HS1-Can bus to wake and communicate IDK.
BCM shedding power, Sticking Relay are my 2 most likely and with-it being a 3-to-10-minute recovery. I am going with a relay; the relay is allowed to relax and then a power cycle brings the bus back online (wakes) and then all is normal.
I have it narrowed down to a (Micro) but what specific is taking down the BUS, it's just theory at this point. It may just be the BCM micro not waking and a power cycle across the Assy Relay wakes it.
I guess we need to be thankful that this is a RARE event, but it would be nice to actually pinpoint exactly what it is.
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.
- 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.
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.
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)
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.
EDIT: UPDATE 10/22/24
I have done some more digging and noted after looking into an Aftermarket Remote Start Issue.
I think I have found the most likely culprit for the Door Unlock Issues & Starting Issues as well as Courtesy Lighting not coming on when the door is opened.
This is the MAIN & PRIMARY (Micro- Controlled Relay) that MUST close for the BCM to Wake and allow Door Locks, Starting, Courtesy Lighting Etc to function.
This (Micro-Controller) Relay ties into all issues - It is internal to the BCM
This Micro is on the HS 1 Can Network and it is a very important controller as this is the primary thing that needs to close when a request is sent via FOB -Door Lock/Unlock - Remote Start, Wake Door Open, Start Request (Key/PB)
Door Unlock Request (FOB) - RTM is receiving the request and sending the request signal to the BCM via (LIN) the BCM is taking that request and triggers that Micro to close.
Now be it Lazy Relay or Low Voltage as the (BCM- Monitoring) Low State of Charge & Load Shed Request are on this HS-Can 1 circuit.
I am thinking it is just (LAZY) once in a while.
So now you manually unlock the door and get in and attempt to start (Nothing - Dead)
You have now - activated 2 timers in the BCM, one is the 3-Minute Timer for the PCM Power Relay, and the other is the 10-Minute Accessory Delay Timer.
The 3-Minute Timer (Normal Ops) will open the PCM Power Relay (If it does not see an engine start) in those 3-Minutes.
The 10-Minute Timer will open - when either 10-Minutes has elapsed, or a door is opened.
Remote Start (Ford Pass) uses the TCU - but communicates to the GWM - Via HS-Can 4, which then communicates that request to HS-Can 1, which triggers that (Micro) relay in the BCM.
So basically, no matter what you do, which avenue you use to enter or start the truck it takes this Micro-Control (Relay) to close.
The reason for it to magically start working is the Power Cycle across it and I think it has to do with the 3-Minute Timer (providing an internal reset) as well as the 10-Minute Timer.
It is this or the BMS has triggered a Load Shed (Reading a low SOC) and the power cycling in the BCM reactivates what it is load shedding - or just simply a Low Battery Voltage (At Wake)
Edit: 1/21/25
I wanted to update and highlight exactly what this (Micro) does and how it relates to the issues.
This is the (BCM) controller for the send & receive of all (HS1-Can) bus data.
So, if the BCM cannot send or receive the data then the bus is dead.
There is a lot of data that is transmitted on that bus but for this specific issue the following are specific to this issue.
This Data originates from the BCM
1. Door Ajar - This is important as this triggers the PCM wake
2. Vech Lock Status - Door Unlock / Lock status
3. RKE Data - This is the BCM authorizing the FOB functions
4. Accessory Delay (Relay) (The 10-Minute) Timed Relay - That I suspect may be sticking
5. Ign Status - So Ignition Switch Position or ISP-R (Run)
6. PATS Control Command
7. Batt Low SOC
8. Load Shed Req
9. Power Shed Level
So exactly what specific is not allowing the HS1-Can bus to wake and communicate IDK.
BCM shedding power, Sticking Relay are my 2 most likely and with-it being a 3-to-10-minute recovery. I am going with a relay; the relay is allowed to relax and then a power cycle brings the bus back online (wakes) and then all is normal.
I have it narrowed down to a (Micro) but what specific is taking down the BUS, it's just theory at this point. It may just be the BCM micro not waking and a power cycle across the Assy Relay wakes it.
I guess we need to be thankful that this is a RARE event, but it would be nice to actually pinpoint exactly what it is.
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