2004 Volvo v70 error code U0073

samizzy1 · Post by **samizzy1** » 21 Sep 2017, 12:51

My car starts, no gauges are working. Trans seems to be funny when going up driveway.
Code reads says computer control module stop
Any ideas?

Post by **precopster** » 21 Sep 2017, 15:41

Reseat the ECM and TCM into the socket and also clean the terminals on both ECM, TCM and vehicle. You may need to purchase the tool to do this or remove the housing and push back those pink sliders.

Sounds more like a CEM (central electronic module) malfunction but don't lose hope just yet.

kellerwaldron · Post by **kellerwaldron** » 16 Mar 2020, 11:06

I have the same problem, sometimes my trans doesn't report what gear its in, sometimes my engine dies on start up, recently my rpm gauge wasn't working. Did you find a solution samizzy1?

22volvo · Post by **22volvo** » 28 Oct 2020, 11:41

Add me to the list for my 04 V70 with a U0073 (comm bus A fail) and subsequent difficult starting.

Digging deeper.....
SRS and TCM reveal no codes
ECM reveals:
ECM-9400: Brake Pedal Sensor signal missing
ECM-928c: Communication error faulty signal
ECM-720a: Immobilizer Communication Signal Missing (reason for no start issue)
ECM-E003: Configuration Fault, Faulty Configuration
ABS/BCM reveals:
BCM-0100: Communication Problem w/ ECM
Freeze Frame Data reveals these codes were latch at RPM=0

Note, had the CEM reworked by Modex with no problems for two years and a recent heat soak on the CEM currently does not trigger this problem.
I'm going to locate a comm bus module diagram and a wiring diagram and attempt to isolate it to the ECM or the wiring or anything corrupting comm bus A.

22volvo · Post by **22volvo** » 29 Oct 2020, 10:49

Update.
After sitting overnight found the following:
battery voltage at rest 12.4v
battery voltage with key in starting position but not attempting to crank 11.9v
battery voltage after starting 14.3v

Time for a new battery.