Replacing VZ ECU - Options in today's Market

[manuelmanuel]

I have been driving around with the low fuel fault on my VZ for a few months now, gauge does read, stays on empty however litres of fuel used counts, the BCM has not failed as of yet.
When I went into the local car shop, it was explained to me that it could be the BCM or it could be the fuel sender in the tank.
There is a way of testing the fuel sender by bridging the pins near fuel tank, when you bridge the pins your fuel gauge should move.
Hope this helps.

 

[crowey]

By anychance... did you clean the engine bay?

Nope.. Only with a damp rag well away from any electrics..

Probably a good idea. Instead of getting it diagnosed in the first place you've gambled, replaced a crapload of modules it probably didn't need, and ended up exactly where you started. Could be a bad earth or a bad bus connection which new modules are unlikely to have fixed. Could be a programming issue too but too hard to tell shotgunning it over the internet.

True if I don't get an ecu com's failure code it was a waste but worth the gamble for what I paid. On the flip side of it if it does throw that code the recommended fix is a new ecu which would have cost me $750+ and by the looks of it would not have fixed the problem. Just very strange that after the swap it started perfectly but after its first long drive all faults come back ..

I have been driving around with the low fuel fault on my VZ for a few months now, gauge does read, stays on empty however litres of fuel used counts, the BCM has not failed as of yet.
When I went into the local car shop, it was explained to me that it could be the BCM or it could be the fuel sender in the tank.
There is a way of testing the fuel sender by bridging the pins near fuel tank, when you bridge the pins your fuel gauge should move.
Hope this helps.

Thanks strange though with mine it won't even crank without bridging the starter. Worth a go.

 

[TazzI]

Nope.. Only with a damp rag well away from any electrics..

True if I don't get an ecu com's failure code it was a waste but worth the gamble for what I paid. On the flip side of it if it does throw that code the recommended fix is a new ecu which would have cost me $750+ and by the looks of it would not have fixed the problem. Just very strange that after the swap it started perfectly but after its first long drive all faults come back ..

Thanks strange though with mine it won't even crank without bridging the starter. Worth a go.

Only time Iv heard of repeat offenders on ECU's is after a lovely engine wash. Or could have been the most unlucky person alive to have actually picked up a semi almost dud set.

Need to see if the ECU is still communicating, get some codes out of it and see what the go is. Not cranking isnt a good sign for the ECU..

 

[crowey]

I put my hand on the ecu after running and can't believe how hot they get..crazy positioning

 

[TazzI]

I put my hand on the ecu after running and can't believe how hot they get..crazy positioning

Ill have to pull the heat reader and take a reading for the bench setup. They get hot when left running on the bench... with nothing connected to it at all.

 

[ForestVt]

I experienced similar problem six months ago.
Immediately after turning the key to starting, (a) Message low level of fuel, (b) key coded correctly recognized by BCM - means padlock sign off on the panel, (c) no popping sound of the drive starter contactor after turning the key, (d) three audible tones failure alarm, (e) low level of fuel message on the display,
...and nothing happens. The starter motor not triggered.

In all cases, all returned to normal after about half hour. In the local GM dealership, using the TECH2, the expert did not identify any error on at least two occasions. When I wanted the recriate the problem, I could not. Not reproducible.

Via web search found similar reports that pointed to basically two suspects (excluding failure in ECU):
1 bad connection somewhere in the CAN network.
2 - Electrical interference generated by a relay with bad contact in the car.

I put my scanner (PC Touchscan and OBD2 adapter) in the luggage. Immediately after an event (in downtown), using my scanner I could identify registered DTC U0100 (network failure - Loss of communication ECM / PCM "A").

What did I do:
I opened all the CAN network connection points and cleaned with contact cleaner spray.
In the relays allocated by the motor box, and tambám the relay box under the dashboard, identified at least four relays that were activated immediately after turning on the ignition key. I replaced these four relays for new (two of them already had discoloration on heating (!!)).

The problem disappeared. Despite I have not specifically identified the cause of the problem, in my case, this action of relatively low cost, eliminated the problem.

I hope this can be of help.
Tazzi (please) can enlighten us something that eventually I have not noticed here.
(I join the Croewy to thank you for your always welcome clarification)

 

[TazzI]

I replaced these four relays for new (two of them already had discoloration on heating (!!)).

Extremely heat from relays normally indicates poor grounding connections? Do the new relays get hot also?

I havent seen it on a commodore, but the old mans 4WD had issues with bad connections, causing the ignition relay to be extremely hot, and lead to its failure very quickly.

 

[crowey]

I experienced similar problem six months ago.
Immediately after turning the key to starting, (a) Message low level of fuel, (b) key coded correctly recognized by BCM - means padlock sign off on the panel, (c) no popping sound of the drive starter contactor after turning the key, (d) three audible tones failure alarm, (e) low level of fuel message on the display,
...and nothing happens. The starter motor not triggered.

In all cases, all returned to normal after about half hour. In the local GM dealership, using the TECH2, the expert did not identify any error on at least two occasions. When I wanted the recriate the problem, I could not. Not reproducible.

Via web search found similar reports that pointed to basically two suspects (excluding failure in ECU):
1 bad connection somewhere in the CAN network.
2 - Electrical interference generated by a relay with bad contact in the car.

I put my scanner (PC Touchscan and OBD2 adapter) in the luggage. Immediately after an event (in downtown), using my scanner I could identify registered DTC U0100 (network failure - Loss of communication ECM / PCM "A").

What did I do:
I opened all the CAN network connection points and cleaned with contact cleaner spray.
In the relays allocated by the motor box, and tambám the relay box under the dashboard, identified at least four relays that were activated immediately after turning on the ignition key. I replaced these four relays for new (two of them already had discoloration on heating (!!)).

The problem disappeared. Despite I have not specifically identified the cause of the problem, in my case, this action of relatively low cost, eliminated the problem.

I hope this can be of help.
Tazzi (please) can enlighten us something that eventually I have not noticed here.
(I join the Croewy to thank you for your always welcome clarification)

Thanks mate - some good ideas. From memory the BCM relay has some discolouration at the top so worth pursuing - may look to replacing a whole bunch of the relevant ones like you did as well as double checking all ground points etc
Need to find a good diagram of all the earthing points on a VZ as i suspect a few are well hidden.

 

[TazzI]

Thanks mate - some good ideas. From memory the BCM relay has some discolouration at the top so worth pursuing - may look to replacing a whole bunch of the relevant ones like you did as well as double checking all ground points etc
Need to find a good diagram of all the earthing points on a VZ as i suspect a few are well hidden.

*Cough* Oh, look, a grounds location image suddenly appeared! :beer chug:
If theres any others you need, let me know.

 

[crowey]

Thanks again mate - you are a life saver!