dr.hammer

I keep getting CAN Bus communication codes at the EBCM (Electronic Brake Control Module):
U0100-7F – Lost communication with Engine Control Module
U0101-7F – Lost communication with Transmission Control
U0140-7F – Lost communication with Body Control Module

2014 Express 1500 LS passenger 5.3L RWD with Stabilitrak 90k miles
I'm not the original owner and don't know the history of the vehicle.
New/fully charged battery.
Runs fine with no driveability issues

No check engine light. When I do a diag scan Service Traction Control pops up and goes away as various modules are scanned (I see no pattern).

I've done CAN bus voltage and resistance tests with a multimeter and see no issues. Visually inspected fuses, main grounds, connectors and harness throughout (body to frame strap looks a little greenish but it's secure)

Using Xtool D8, and confirmed codes with Innova scanner at parts store. I clear the codes and most times they immediately come right back without driving. I can read live data for all modules including EBCM live data, and perform ABS and solenoid actuator tests (activate pump, solenoid valve checks, etc). I've unplugged the EBCM and checked powers and grounds - no issues.

Front hubs/sensors are new (ACDelco). When performing rear solenoid valve tests with the D8 (rotate wheels for free spin, apply brake, rotate wheels and check to see if they spin again, etc etc) the rears fail portions of the test (they don't spin when they should or the opposite - getting mixed results). Not sure how accurate these tests are and I don't see how this is related to the CAN bus communication, but possible? Driving test shows all wheels showing the same speed.

Any thoughts/suggestions on what's causing the comms codes and where to look next? Trying to rule out basic issues and avoid a trip to the dealer. If it sounds like the EBCM (not the pump), I'm open to sending it in for repair/resolder if anyone know a reputable source.

mountainmanjoe

Sometimes control modules just fail. Take it to an auto electronics specialist.

funtwodrv

We're seeing similar issues with U0140 code. Were you able to identify the source of this issue?

Charles Martin54

Got a tip for you on those CAN Bus gremlins. It's all about giving your wiring and connectors a thorough once-over. Found the culprit on mine: a sketchy pin on the EBCM connector. A little elbow grease, some contact cleaner, and it was like I'd rebooted the van's brain. Sometimes it's the little things that make a big difference.

Give your rig the attention it deserves and you might just sort those codes out yourself.

funtwodrv

Thanks, I did remove the connectors from the ECM and the BCM and sprayed them with contact cleaner. I didn't notice anything but, will take another look when its back from the shop. Right now, it's at a Chevy dealer today so they can run their diagnostics on it as it started displaying the air bag and passlock lights on the instrument cluster but, I wasn't seeing any new codes on my Autel. I should get some feedback from them on Thur. I would not be surprised it they tell me it's a "wiring" issue! This thing is getting too sketchy to trust.

IHaveAHeadache

Were you able to find out whats going on with the van? I have this exact problem with one im working on now and just scratching my head

IHaveAHeadache

If i turn the key on and press the gas pedal the ebcm sets u0100:7f lost communication with ecm bus signal erratic and if i press the pedal enough times it sets u0073 can bus A off in ecm. ive tested the wires from pedal to ecm and theyre good. unplugged ebcm and bcm and still sets u0073 in ecm if i press gas pedal enough times. scoped the signal to pedal sensor and the waveforms both match each other. im kinda lost haha

funtwodrv

Yes, the bcm was loosing the low speed data stream to the instrument cluster and the radio. Had to have Chevy replace and program it.

IHaveAHeadache

thats what fixed the traction light flashing on? I could see that fixing your airbag and passlock lights but that shouldnt have an effect on the ebcm issues. i know the ebcm runs through the bcm to the ecm but thats all high speed can and instrument cluster and radio are low speed

funtwodrv

We’ve been dealing with intermittent issues with the dic and instrument cluster, no crank etc for well over a year. So far, replacing the bcm has resolved all of them…