Questions and Answers

Buick Riviera Quad Driver Fault Q. To whom it may concern, I have a 1995 Buick Riviera. it has a 3.8 liter supercharged engine that is backed by an automatic transmission. The Car has been good to up till now. It just hit 120,000 miles today. The car is fuel injected.

I am having problems with the car surging at idle in drive or reverse. The entire car "hops", the engine moves as though it is going to break free. From reading articles from your site I decided to change the EGR valve and oxygen sensor. A local shop gave me a diagnostic for $60.00. The results came back as follows Codes: Quad Drive motor, O2 sensor low, EGR pintle position error.

This was performed on a Snap-On 2500 diagnostics machine. The shop informed me they would have to do more work to find out what was causing this problem ($60.00 more). This problem only occurs after the check engine light comes on. This happens when the car has been warmed up for five minutes or so. Since this problem started the car has started to run hotter than normal. Do you have a helpful suggestions?

Sincerely,
Ryan

A. You should let them follow the diagnostics for the quad driver fault. This is a sort of relay inside the PCM that can sense a short and trip like a breaker. Chances are the problem will show up in the trouble chart for this code and may take care of all the problems. It's called quad because it can control up to four things on each driver. The wires to the EGR valve or the TCC could be shorted somewhere.