ECU or BCM issues VZ Calais

[Stavros.A]

My VZ Calais V6 has now twice on separate occasions just suddenly stalled on me in traffic (on idle). After starting it again the transmission begins to play up locking up when changing from 3rd to 2nd and 2nd to 1st. This stops and goes back to normal after I switch it off and lock it and unlock it. I have also had a couple of other issues with headlights not turning off on auto mode and the fuel gauge playing up but these return to normal also. I suspect one of the computers but have no idea which one. Intermittent fault can be a pain so no idea where to start. The car has 135k on it. wondering if anyone has had anything similar or has any idea on where to look for a fix? Thanks.

[IJ.]

Alternator/Battery condition?

[Stavros.A]

new battery alternator is ok car is up to date with services

[IJ.]

Worth getting them checked out as VZ's do some weird shit if either is not 100%, another point to check would be the ABS Module as for some bizarre reason if you unplug it you lose a lot of the dash including the fuel gauge..

[Stavros.A]

at first i thought it was the trans so i took it to a trans guy who hooked up a tech 2 and said it was not the trans but one of the computers or modules but he couldnt say which. he did say there was a fuel gauge error and a communication loss error. he said it would be difficult to pinpoint because it only happened twice in 2 months so im not sure where to go from here.

[Micks]

at first i thought it was the trans so i took it to a trans guy who hooked up a tech 2 and said it was not the trans but one of the computers or modules but he couldnt say which. he did say there was a fuel gauge error and a communication loss error. he said it would be difficult to pinpoint because it only happened twice in 2 months so im not sure where to go from here.
What your explaining is possibly a faulty or intermittent PIM module. Have seen in the V6's the fusible links can cause similar problem.

[Stavros.A]

thanks the PIM is one of the suspects but there must possibly be a second problem re the headlights not turning off on auto mode and the fuel gauge errors. intermittent is the problem it makes it difficult to pinpoint.

[Micks]

Yes my Z does the headlight thing ever occasionally, something not right in the BCM I think.

[Stavros.A]

my fuel gauge appears to be off as well. last fill it showed i used 47l and the pump said 53. i also have a vx berlina which is always within 1 litre

[Woodchukka]

Wife has 3.6 AlloyTec in VZ wagon and it has started to have intermittent stumbles at idle. Had only stuttered on me once before the other day and it was doing it for a short period at every set of lights. It was a hot day in stop start traffic. Fuel econ, gauge and DTE all seemed normal and shift was a little rough but it is a bit sometimes. I had a hunch and turned off the A/C as it appeared to be when it cut in. The stumble did not occur when the A/C was off. I tried this over several sets of lights and waited for the stumble to start and then turned off the A/C. I have not had the time to look into it as yet however for mine it appears to be a fault in the idle compensation when the A/C cuts in. Does not happen when selecting a gear though.

[Stavros.A]

Wife has 3.6 AlloyTec in VZ wagon and it has started to have intermittent stumbles at idle. Had only stuttered on me once before the other day and it was doing it for a short period at every set of lights. It was a hot day in stop start traffic. Fuel econ, gauge and DTE all seemed normal and shift was a little rough but it is a bit sometimes. I had a hunch and turned off the A/C as it appeared to be when it cut in. The stumble did not occur when the A/C was off. I tried this over several sets of lights and waited for the stumble to start and then turned off the A/C. I have not had the time to look into it as yet however for mine it appears to be a fault in the idle compensation when the A/C cuts in. Does not happen when selecting a gear though.

the revs on mine do go up and down on idle all ocassionally with the a/c on or off. my issue has happened twice since i have owned the car which is only 3 months. other than an up and down idle (which is not that bad) the engine and trans run really nice. my engine just simply "cut out" describes it better than "stalled" 2 times on idle and when i restarted it thats when the trans started playing up. not sure about the fuel gauge either as on my last fill it showed fuel used was 47litres and it took 53 to fill....my vx was accurate to 1 litre...