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Quad Driver Circuit Trouble Code

1994 Buick Park Avenue Ultra; 170K+ miles


1. ECM replacement five years ago

2. About six months ago car would crank and not start. Accessories also failed, no power window, no power seat.

3. Repair shop finds bad ground at fuel tank. Explains: hence fuel pump won’t work - that’s why lots of crank and no start. Also finds ground block under seat bad, hence no accessories. Both issues repaired.

4. Few weeks ago - little red light on volt meter is coming on intermittently. Sometimes seems to coincide with hitting bumps in road?

5. Alternator and battery both test OK, both fairly new within previous year.

5. SES light along with alternator light. On cold start up volt meter is slightly into red zone at top of scale, drops back to normal range after a few minutes

6. Occassionally getting hint of electrical odor in passenger compartment. Burning? Overheating?

7. Different repair shop. Tell them all of above. They scan and tell me Quad Driver circuit but they don’t know which one. Bring car back for two hour test early one morning.

8. Next visit repair shop clears code. Drives car twice. Two hours later they say can’t find anything wrong. Say some kind of intermittent problem. Bring it back so thay can have it first thing one morning and test all day.

Anyone - Suggestions on next course of action?

Quad driver circuit…TV repairmen use terms like that, until they all went out of business.

The marriage of electronics and automobiles has been a very bumpy road…Good luck…

Here is a link to a thread that talks about Codes 26 and 56. There are two quad drivers appearently and they each can drive up to four different circuits.

Related info about codes:

If there are currently no problems then you may have wait until something shows up again. If you still smell a burning oder I would check things under the dash and look for signs of burning due to a bad connection.

Thank you very much for the suggestions -

Take it back to the first shop. You have to lay hands on a car and do real diagnosis to find a bad ground at the fuel tank. That’s the sign of a good mechanic.

The other shop couldn’t fix it because the computer didn’t tell them what part to change. Sign of a parts changer. Stay away.

  1. Quad Driver Circuit problem: it took A LOT of testing/driving with scanner to find it - bad solenoid in the transmission.
  2. Alternator Light: tested and tested - alternator fine - battery fine - suspect bad instrument cluster - confirmed when light next came on - whacked top of dash and light went out.

Hope this might help someone in the future -