Computer problem
2003 Buick Rendezvous 6 cyl Front Wheel Drive Automatic 56000 miles
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BCM module seems to be loosing power. Allarms keep on going off in random. They reset or trigger when tapped on stearing wheel. Buick dealer mechanic works on it for last four weeks. He changed BCM - no improvement. He plugged in temporary or disconnected a number of switches and sensors that work with BCM - no improvement. He found couple wires with stripped unsulation - no improvement after repair. Mechanic is still going through ground points, wires and connectors. Problem affecr a power in a way that there are no codes set indicating problem. Diagnostics check o.k. or don't work at at all due to interrupted communication.
After 4 weeks - it looks like a challenge. What would you say gentelmen ?

I would have thought a BCM update, but that was done. There are some issues that end up being an ignition switch..the tap test on the steering wheel would want me to look real close at that.

Replacing ignition switch didn't fix a problem. This was tried in a the week #1.

Is the reaction still happening when tapping on the steering wheel?

That sounds like a dead giveaway on the problem area.

I'll take a look at the diagrams and see what I can learn.

All the grounds been checked at this point?

IF there was an interruption of communication, that in itself would set a code in the pcm..u1000 I believe.

On Friday 08/08 I picked up my car from dealer's service shop. Technician told me that he checked all ground/chsse termination except those under seats under carpet. He checked connectots on harness, wiggled wires in search for breaking conductors. There was no definitive find. They put 186 miles driving car without reoccurence of problem. They concluded they hopefuly problem was in one of chssis terminations of ground wire and it was taken care of.
After driving car for two days without incident, it finaly happened just about an hour ago. After cars been switched on a driveway I decided to move up Randezvous a little closer up the driveway to clear a sidewalk. To my supprise engine wouldn't start. I could hear control relay click-in, but starter's bendix never attempted to kick-in. I had this symptom as one of many along with loosing power on gages, cluster, radio, along with alarms on display and chime going "on" and "off". This time there were no allarms.
-- Correction. I wasn't shure if the radio was going off so I went to check. This time engine started o.k. from a first try.
I hope you understand that it is not my best day or month in my life. I need this car to become again reliable.
Any ideas?

I think that I would treat this as a separate symptom from the rest. This might be a multiple problem situation. The dealer may have repaired the other issues, but a problem in the starting system may still be present. With intermittant problems, nailing them can be tough. The testing has to happen when the no-start is present. I would check for power getting to the starter when the no-start occurs, if power is there, then it needs a starter. If power is not there, then you need to find where the power is stopping.

Problem with start failure had been rectified. After changing BCM module the technician had only one key. Car failed to start with a second key. I programed BCM for it and it's O.K. now. It means that car shows no ill simptoms after picking it up last time from the dealer's shop. It means also that I will never be able to pinpoint exactly where the problem was. I assume - it was one of grounds or connectors - but wchich one? I hope it will not ever come back to hunt me. Thank you for your concern and help.
MZ

So a second BCM was installed?

The first one was reprogrammed wasn't it?

BCM was replaced only once.