Intermittent issue Bcm/ecm

[George Owens]

Good afternoon all, I’m at my wits end with this thing. I’m having intermittent issues with my 08 Tahoe. 185k the dash will either act wonky (if I have the range device plugged in). or gauges will drop (if no range plugged in.
Codes that came up always seem to be u0140 ( lose communication to bcm) or u0100 (lost communication with ECM) that’s with range plugged in, without it those 2 pop up along with u0102 ( lost communication with transfer case controls module) and u0101 (lost communication with transmission control module)

What I’ve changed so far Is the
Ecm,Bcm. Negative battery cable, mega fuse, battery (bad battery) , terminal resistor under the spare. I’ve taken off the abs module under the car and put diaelectric grease on it

Yesterday it acted up, plugged the range in while I was still driving and it acted normal. Then I unplugged it and it was fine till I got home

Any leads would be appreciated

 

[ScottTheEngineer]

Same problem just fixed yesterday. Under the lower fuse box between the 12vbattery and the radiator is the ECM. connected to that is a blue multipin cable connector. Cable has 16 #22 wires in it. The cable routes straight down across the frame and into everywhere else. My frame had rubbed through the cable insulation and about 6 wires. The battery positive voltage wire (Red/Wht) was shorting to the frame. Several others were rusting out. I imagine if you did the ECM already You would have seen it but doesn't hurt to check.
Good Luck!!

 

[B-train]

Wow! Good find. Thanks for sharing. I will keep that in mind next time I'm under the hood.

 

[Geotrash]

Same problem just fixed yesterday. Under the lower fuse box between the 12vbattery and the radiator is the ECM. connected to that is a blue multipin cable connector. Cable has 16 #22 wires in it. The cable routes straight down across the frame and into everywhere else. My frame had rubbed through the cable insulation and about 6 wires. The battery positive voltage wire (Red/Wht) was shorting to the frame. Several others were rusting out. I imagine if you did the ECM already You would have seen it but doesn't hurt to check.
Good Luck!!
View attachment 388798

 

[George Owens]

Same problem just fixed yesterday. Under the lower fuse box between the 12vbattery and the radiator is the ECM. connected to that is a blue multipin cable connector. Cable has 16 #22 wires in it. The cable routes straight down across the frame and into everywhere else. My frame had rubbed through the cable insulation and about 6 wires. The battery positive voltage wire (Red/Wht) was shorting to the frame. Several others were rusting out. I imagine if you did the ECM already You would have seen it but doesn't hurt to check.
Good Luck!!
View attachment 388798

What year is your car? And are you like under the car? And you was getting the same codes?

 

[ScottTheEngineer]

I had several different U-codes. Engine was shutting off randomly.
The wiring is accessed from underneath the 2009 tahoe hybrid. The hybrid stuff is all on passenger side of motor. Remove bunny thumper and it's on the driver side just behind radiator over frame
I fixed it with sealing butt splice connectors and wrapped the shit out of it with several different layers of electrical tape.
The pic shows where I isolated the rub through wires with a small piece of tape before sealing.

 

[George Owens]

Gotcha, mines was more up top but I’m guessing that’s where you saw rubbing at, I don’t think I would have that issue seeing as thought everything is covered with wire protectors but it

’s still worth a look

 

[George Owens]

Still nothing what about you guys?

 

[swathdiver]

Hey George, your video this morning popped up in my youtube feed, I thought you were sliding there for a second!

I am looking at the wiring diagram for the cluster, the gauges to the ECM, there is a Dark Green wire and a Brown and White wire that you might want to check. But that doesn't explain the door locks so I came across the Red and White wire from Fuse 46 (J4 or X4) that goes to your cluster (Pin1). There may be a problem with the pins on the fuse, the circuit board itself or a wiring issue or nothing at all and I'm wrong. Tracing wiring problems is not something I'm good at.

For the Door Locks, they get a signal from that Dark Green wire too, that is the LAN network so maybe there's something wrong with that wire or the connection at either end.

Can y'all see this diagram? I see it during edit but not after saving and posting. OK, Fless, I used another diagram and the Snipping Tool.

The GMLAN Dark Green wire in this diagram goes to the ECM.

 

[Geotrash]

Hey George, your video this morning popped up in my youtube feed, I thought you were sliding there for a second!

I am looking at the wiring diagram for the cluster, the gauges to the ECM, there is a Dark Green wire and a Brown and White wire that you might want to check. But that doesn't explain the door locks so I came across the Red and White wire from Fuse 46 (J4 or X4) that goes to your cluster (Pin1). There may be a problem with the pins on the fuse, the circuit board itself or a wiring issue or nothing at all and I'm wrong. Tracing wiring problems is not something I'm good at.

For the Door Locks, they get a signal from that Dark Green wire too, that is the LAN network so maybe there's something wrong with that wire or the connection at either end.

Can y'all see this diagram? I see it during edit but not after saving and posting.

The image isn't coming through for me, James.

 

[Fless]

Hey George, your video this morning popped up in my youtube feed, I thought you were sliding there for a second!

I am looking at the wiring diagram for the cluster, the gauges to the ECM, there is a Dark Green wire and a Brown and White wire that you might want to check. But that doesn't explain the door locks so I came across the Red and White wire from Fuse 46 (J4 or X4) that goes to your cluster (Pin1). There may be a problem with the pins on the fuse, the circuit board itself or a wiring issue or nothing at all and I'm wrong. Tracing wiring problems is not something I'm good at.

For the Door Locks, they get a signal from that Dark Green wire too, that is the LAN network so maybe there's something wrong with that wire or the connection at either end.

Can y'all see this diagram? I see it during edit but not after saving and posting.

If you can't get it to post see if you can PM it to me as an attachment and I'll see if I can figure out why it doesn't show up.

 

[swathdiver]

Bump for George. @George Owens

 

[George Owens]

Here’s a update pretty much it finally gave out last night don’t seem to be random now

 

[George Owens]

Has this box (near the drivers feet) known to intermittently act up? I have wiggle wires/tap the box and it went back to normal, I checked all wires and see no issues so I put dielectric grease on the connectors and re-connect but I’m eyeballing this box because it went back to normal when I wiggled/slapped this box (giggity)

 

[Geotrash]

I believe the technical term is "percussive maintenance"

Any electrical component where there are a ton of wires and connection points is a potential problem. Sounds like you may have a solid lead, finally.

 

[George Owens]

I believe the technical term is "percussive maintenance"

View attachment 392161

Any electrical component where there are a ton of wires and connection points is a potential problem. Sounds like you may have a solid lead, finally.

So it’s possible for that to act up intermittently?

 

[swathdiver]

View attachment 392160

Has this box (near the drivers feet) known to intermittently act up? I have wiggle wires/tap the box and it went back to normal, I checked all wires and see no issues so I put dielectric grease on the connectors and re-connect but I’m eyeballing this box because it went back to normal when I wiggled/slapped this box (giggity)

Never had a problem with them or read about folks having trouble with them but anything can happen George. That's called the Body Wiring Harness Junction Block, 20813086.

It comes apart, so maybe a circuit needs resoldering inside?

 

[George Owens]

Never had a problem with them or read about folks having trouble with them but anything can happen George. That's called the Body Wiring Harness Junction Block, 20813086.

It comes apart, so maybe a circuit needs resoldering inside?

I wouldn’t know what to do solder wise I did order one that might not get to me till Tuesday, it acted up again today on the way to work was fortunate to make it and it went back to normal. I watched this video which also makes me suspect the junction box more so watch it from the middle to the end part. I did get 98 ohms at one point, but I didn’t get a chance to remove the junction box like he did to 100% single it out before it went back to normal.

 

[swathdiver]

Good job getting it narrowed down! That's a new one for me.

 

[George Owens]

Welp I just switched it out now we wait