1995 Buick Riviera



May, 21, 2010 AT 5:12 PM

Computer problem
1995 Buick Riviera 6 cyl Front Wheel Drive Automatic 135365 miles

This year is a pain, between OBDI And OBDII. But I managed to obtain trouble codes and need help. Following codes are present:
P0406-EGR Pintle Valve Position error
P0568-CC System Sensor Signal Circuit Problem( car surges when cruise control set. Tests show system works and deactivates when brake applied, but surges when on)
P0599-VATS failure(pass lock II system-tried both keys I have and car still runs)
P0650-Quad Driver Module QDM2 fault
P0705- PRNDL Switch fault
used Actron cp9150
Need help. Where is the PRNDL switch? EGR valve is no brainer. Quad driver QDM2? Where is that and what do I look for?
Cruise control-switch on cloumn or in engine compartment?

Had it in dealer for other issues and ever since I got it back these came up. Had issues with dealer and turned them into BAR. So any help you can give me to fix this would be greatly appreciated. I love this car and the way it handles.

3 Answers



May, 22, 2010 AT 8:22 AM

PRDNL switch is on transmission where cable connects.

Quad Driver Module QDM2 fault is a PCM (engine computer) error.

Cruise switch is switch you push to engauge cruise.

I would concentrate on PRDNL switch, if PCM does not know what gear it is in, cruise will not engauge.

Quad driver will have to be scanned by dealer or trusted garage.



May, 23, 2010 AT 12:11 AM

The cruise works. I can set it and brake deactivates it. However, engine surges when cruise engaged. So would the prndl switch cause that and cause the QDM2 fault, or is the cruise solenoid possibly bad? At this point I really don't trust anyone but myself to work on this car. I need a good shop mannual specific for this car, not a generic haynes or such one.



May, 23, 2010 AT 8:37 AM

Go to public library or community college. Get on a computer and go to Mitchell or Alldata. Com.

These are repair instructions mechanics use.

Take yor trouble codes with you, you can troubleshoot each code using the flowcharts available from mitchell or alldata.

Most CC's and libraries offer this free.

You can go to the above mentioned sites at your home computer and download an electronic manual for your car, cost is usually $20 or so.

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