Can not find instruction on how to remove BCM on 2020 ranger

[mikeamick]

what is the specific code it shows?
I am looking for Internal Error code.

Ok, I'll look today.

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[shovelhd]

Have you load tested the battery? These symptoms, as well as the ASS disabling itself, point to a bad battery.

 

[mikeamick]

Have you load tested the battery? These symptoms, as well as the ASS disabling itself, point to a bad battery.

Man, that would be nice. I wish I had the means to load test it. The battery only died one time, and never even seemed to be "low" after that. But hard to argue with an EE, so maybe I'll take it to
autozone or similar to have it tested.

thanks Chris

 

[mikeamick]

Ok, took the truck for a scary trip around the block hoping it wouldn't light up and strand me
having to call a tow truck. I drove it hard accelerating stopping jerking etc

Anyways ... there was no engine light or any other warnings. Everything worked good. Hooked
up the scanner and only 1 code popped with a couple of stored ones.

 

[airline tech]

Which side of the truck was damaged?
as the Headlight Codes are (Short to Ground) codes
those codes could be triggering your symptoms and also be triggering the BMS codes but if not.


It looks like a bad BMS sensor, as the most likely - sending invalid data to the BCM, another possible is the 225 Amp fuse may be partially blown or vibration damaged. This is the fuse on top of the BMFL (top of the battery) pull it off and inspect for security of the legs. I suspect it may be bad.
Another way to test - get a meter and measure voltage on both sides of the fuse, if bad you will note a voltage drop on the battery side.

The B11BD-08 is active fault --- & the -48 is historical code

What position was the headlight switch in when you scanned? sometimes if you are out of normal switch position (scanning) may trigger false codes - such as OFF, if you note when doing a BCM self-test (the lights cycle) so false misleading code may be generated.

Now for the Headlight codes, I suspect a bad headlight switch (internally shorting) this is a direct feed to the BCM and as I said the BMS code, and these codes are related to your issue, and I think the headlight switch MAY be the root cause but can also be (since front end damage) can be headlight wiring -but no codes are showing for those circuits, the ones you have are related to the switch itself and the wiring between the switch and the BCM.

Both of these Switch & Sensor can kill the battery voltage to the point of needing a jump and dropping power off of the BCM to basically shut down. I do not think the BCM itself is bad it's a voltage supply issue.

 

[airline tech]

To test the switch and those specific circuits.
Meter (Ohms) scale

To test the switch itself - disconnect the connector and match the pinout to the switch for reference.

Autolamp Circuit. Ohm between Pins 4 & 13 - Cycle the switch positions
You should have (Open) circuits on all except (Auto)

Headlamp (Off) Circuit: Ohm between Pins 4 & 10 - Cycle the switch positions
You should have (Open) circuits on all except (Off)

If you have continuity in any position other than noted above - the switch is bad and shorted internally.

So might as well test the other circuits:

Headlamp Pins 4 & 12, open circuits except Headlamp
Parking Pins 4 & 11, open circuits except Parking

Use this as a ref for the pinout to test the switch itself, this is the connector for the switch, but we need to test the switch positions (component side)

 

[mikeamick]

Ok, I'm starting to feel like someone that thinks they know a lot standing talking
to guys that really are experts. The tests and theories all sound legit but I think I
am going to drive it and collect more information.

But Here's some ugly additional info.

The truck was hit passenger front, but am afraid to admit that the BMS cover was
cracked. After all the lights went off and the truck wouldn't start, I just pulled the
battery cable and got it home. When I hooked my scanner up it seems to me that
the BCM was showing 7 codes but I was soo shook up that I reset it without looking
at the codes. Even pulling the battery cable might have cleared some codes.

And believe it or not, even AI couldn't find info on how to change a BMS.

But as to the headlights

I always have the headlight switch set to automatic, all the way clockwise. I do find it
interesting that the codes are indicating a short. Pulling the switch doesn't look too bad
so I might check some continuities. I just can't believe that would disable my whole truck.

Oh , and I will check the fuse on top of the battery.

So again, I think I will drive it and hope that some non vehicle disabling codes appear to
help with the clues.

If I disappear for a bit, but find more clues I will come back to this thread instead of
starting a new one.

Mike

 

[airline tech]

Sounds like a plan - monitor it

But I suspect the Root Cause is the Headlamp Switch (internal short)

Now before I proceed, I want to note that I have conflicting information regarding power feed into the switch.

One diagram shows power feed into the switch on Pin #9 fused by a 10 Amp fuse #20 (BJB) however that is a (NOT-USED) fuse location

So, I am going with 2 diagrams that show Switch Power being fed by the BCM itself, so this means that the power feed for the switch is coming off the 125 Amp Fuse feeding the BCM and also explains why you are having issues with (electrical anomalies) or GREMLINS
If that circuit is truly shorting to ground (if those are valid codes) then it would explain the:

1. Dead Battery - Short to ground - Parasitic Draw (engine off)

2. 125-Amp - fuse strong enough not to blow, with this short - so hidden issues

3. Hidden Issues - Voltage Anomalies when engine running inside the BCM - due to the internal short circuit being generated by the switch / wiring between the switch & BCM / Internal BCM circuit short for the headlamp circuit affecting the whole BCM power circuit.

4. This voltage anomaly in the BCM could be causing it to shut down and power off (voltage drop)
this is why the truck died, no start and unable to shift out of drive - The BCM lost power as well as your Hill Start Assist message

Now add in a cracked (BMS) sensor -I suspect this is the reason for the BMS codes, not the 225 Amp fuse. So, this sensor sends battery statis information via the LIN circuit to the BCM to tell the PCM how to charge the battery (voltage state) so this in itself can create battery charging issues.
The only reason I suggested to check the 225 Amp fuse as it ties into the BMS codes, but since it is cracked (we know the reason for the codes) damaged & moisture intrusion

So, both combined can create your issues but the Short Circuit is the Root Cause.

For Ref: The BCM is powered via:

Main Fuse:
125 Amp Fuse (High Current Junction Box) buried under the engine (BJB) Fuse Box; it looks just like the 225-Amp fuse for the Alternator only more difficult to access.
So internally the BCM is using this fused power (as its power source) for the headlamp switch and controlling the voltage supply internally. All circuits are powered and looking for a ground provided by the headlamp switch position.

Secondary Power:
DC/DC Convertor - Powers some circuits after the Run/Start Relay closes

125 Amp Fuse location - BJB Removed, so for any fuse to be checked for damage or security this is the one to check.

So, with what you are posting (information provided) thus far - the Headlamp Switch and or Wiring (Between the BCM & Switch) or (Internal BCM) Headlamp Circuit power feed is the root cause of your issues.
And I suspect the switch is it or most likely of the 3.

EDIT: Somewhere on your scan tool - Live Data - you should see a Module Voltage (PID) for the BCM - See if you can find it and cycle the headlamp switch and watch for voltage jumping around. (Large Voltage Drops) or Erratic voltage

 

[airline tech]

The more I dig on those headlamp switch codes , since the manuals are vague in them , I think it is possible that they are related to the -Auto On-Off of the headlamps (entry/exit)
And may be a misleading set of codes
And triggering due to low battery voltage, not operating normally.

 

[mikeamick]

Ok, some additional info

Took the truck for a drive, and minutes into the ride I got a "Hill Climb Error" , acknowledged
it and kept driving. Got home and wanted to see if that had popped a code but all I saw
was the lights code and a Battery monitor module error. I reset it and checked again and still the
same codes.

BUT .........

As I said before I leave the light switch in the auto position. Just for fun I turned the lights to
off and retested. No lights errors, only the BM Module error.

Maybe I should drive around in the day with the light switch off to see what happens.

 

[airline tech]

The Hill Start Assist Not Available - It that the message?

I want you to try something, since you have a visual cracked damaged BMS sensor.

Disconnect it (The Connector) we need the cracked sensor out of the circuit.

Now take it for a drive, I have a feeling the Headlamp Switch codes, and Hill Start Assist message will disappear.

When I noted that the Hill Start Assist is on the HS1-CAN Bus

1. BMS sensor data is sent from the BMS sensor to the BCM via (LIN Network) dedicated line, so a short in this circuit will be sent to the BCM via the LIN Circuit or it is sending corrupted data to the BCM

2. The BCM transmits the LIN data received over the HS1-CAN Network, so now the HS1-Can network is also corrupted and or picking up the short from the BMS sensor.

3. The Headlamp Switch Status - is on HS1-CAN

4. A part of Hill Start Data is transmitted over HS1-CAN to the PCM

So, I am backtracking some here and taking a different approach to this.
I think the BMS sensor is shorting and is taking down the HS1-CAN bus.
It will not hurt the system to disconnect the BMS sensor, but if it is shorted, it may be feeding that short into the BCM and causing all the issues.

There are a number is data inputs along the HS1-CAN bus such as Ignition Status, and Gear Lever Position but most importantly is the BCM main com is on that HS1-CAN bus.

I think when your engine died - the BMS sensor was in full (short) and completely killed the HS1-Can bus, when you disconnected the battery (negative) cable you jarred the sensor, and it allowed the truck to start.

I want to say, with the truck running tap on the BMS sensor and see if the truck will stall, but afraid to possibly cause more issues than you have, so just try a disconnect and get the sensor out of the system and see how it goes (results)

 

[mikeamick]

ok, the bms I am talking about is a very large box type thing just in back
of the battery. With a few huge plugs connecting everything together.

We must be talking about diff things, I really doubt anything would work
with this disconnected.

 

[RangerBill]

ok, the bms I am talking about is a very large box type thing just in back
of the battery. With a few huge plugs connecting everything together.

We must be talking about diff things, I really doubt anything would work
with this disconnected.

That is the Battery Junction Box (BJB) and contains many fuses and relays that supply power to the truck. I would look that over carefully for damage. Also look at the fuses and connections to the battery positive terminal. Did damage occur to the driver's side as well as the passenger side of the truck?

 

[airline tech]

Ok- Sorry for the confusion here

First, Lets clarify what the BMS sensor is:
It is a sensor that monitors - Battery, health, voltage and current draw and reports this information to the BCM.
This sensor when it's hooked up, plays a large role in how the system charging system operates
and greatly affects how the BCM handles charging commands.

Using this borrowed pic:

The little black sensor - that is on the (Neg) battery terminal is the BMS Sensor aka Battery Management System (Sensor)
This is a current sensor - it has 2 wires.
One wire - feeds over to the (Pos) Post
One wire - feds into the BCM (Lin Circuit)


The - BJB- Battery Junction Box = The upside down (T) in this pic, this is the engine bay fuse box.
It has 2 sides to it - Top & Bottom, to access the bottom of this, you have to remove it and flip it over.
Once removed - you have access to the High Current Fuse Box, posted above this is where the 125-Amp (BCM) fuse is located.

Now: We need to know what CRACKED on the BJB.
The Cover or the Fuse Box itself, this box is sensitive to water intrusion and may be getting water in it - creating issues as well as water getting in the (2) connectors and sitting in the recessed connector receptacles.
Plus, it has been an issue for some to get water down on the High Current Fuse Box and create issues.

So, by chance was it raining or recently driven in a heavy rain when your engine stalled?

This is the - BMFL
Battery Mounted Fuse Link, I have made this little (noted pic) to show what each connection feeds.
Ensure all connections are secure and ensure the small little wedge (block) is in the same orientation as in the pic.
If this is backwards - the (Pos) clamp will not secure tight to the post

The 225-Amp fuse here MAY be partially blown and have a damaged leg, generating a low charging battery - Alternator producing the charge - but not making it through this fuse to actually charge the battery.
One of the pinpoint tests for the BMS Codes is to ensure this fuse is good.
Note it can appear good (visually) but still be bad.
It needs to be tested with a meter - Voltage Check (both sides of it) or removed and (Ohm checked)

I can verify (from another Ranger) that this fuse will create charging issues, visually good and found bad with a meter.

Anyway - As previously posted - I still think your Root Issue is the BMS sensor, or the LIN circuit feeding into the BCM, that is creating the codes you are getting and with the invalid data send to the BCM from the BMS sensor, it is affecting the HS1 -Can Bus.
This is why I want to try to eliminate that sensor from the circuit, just to see if it resolves your codes.
Process of elimination before we continue chasing this rabbit.

 

[Ohwell]

The other day I was driving and came to a stop. All the dash lights came on and complained
about everything from collision avoidance to backup aid. Anyways it wouldn't start
or even come out of drive. With a line of cars behind me, I might add. So I jumped out '
and pulled one of the battery terminals off then back on and it started.

My scanner says bcm fault

Not to mention some quirky electrical activity, like i was trying to drive up a tiny little bank
and the dash freaked out with a hill climbing error. A dead battery another time.

Something like this happened to me a week after I bought my truck. The dealership I bought it from and the closest dealership to me couldn't get my truck in for a few days, I had all kinds of DTC's, the main one was I lost power to the ECM. Frustrated that I couldn't get it into a dealership right away, I popped open the fuse box under the hood and noticed the relay for the ECM was not pushed in all the way. After removing the relay and reinstalling it all the way in the fuse box, my problem went away. The truck died on me 3 or 4 times before I did this, and it would start again if I let it sit 10 minutes or so. It might not hurt to check some of those relays to make sure they are installed properly.

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