1995 Buick Lesabre

I am having trouble finding the meaning of two trouble codes I have for this car. The codes are four digit obd1 codes. I have p0670 and p0640. These are both active fault codes. Please help!
June 17, 2007.

I have no info on either code.

IS there a perfornmance problem or service enginne soon light problem, that made you pull the codes?

Yes the motor runs very ruff when trans. Is put into any gear. I found a short description of the code p0640 from the scan tool that I used from a tool seller I know. It was somthing about the quad 4 system. The hookup for this car has a 16pin connector that a obd2 scanner will plug into but will not read. That's when I looked under the hood and found that it's obd1 certified. It seems that the ruff running only happens when the rpm, s are low. I am a deseil mecanic and have been for ten years. I rebuild engines and know engine management systems. But in the hanyes manual there is know mention of these codes or the quad 4 in the scumatics for the pcm.

Jun 18, 2007.
Ahhhhh. P1640 (illuminates mil light) and p1670 ( does not illuminate light).

That's quad driver circuit. Likley ground problem or moreso a pcm.

The Quad driver is hard wired in to the PCM. To check the drivers, in your case #1 and #3, you need a scan tool to command the driver switch to energize (ground) the circuit while checking with a test light. Alos you need to operate the vehicle in a way that should cause the suspected portion of the driver to switch “on”. There may be circuit breakers that failed to protect the module.

Where might these quad drivers be located and what purpose do they serve? The pcm is the GM factory unit.

Jun 19, 2007.
A quad driver is a component that has four outputs that is controls. IT is part of the PCM, not serviced separatly, it is available aftermarket. You need to pull the pcm and get the part number off of it.

O.K I got the pcm out it's right here in front of me but i'm not sure which # is the part #. Also do you know of any good aftermarket companys to get one of these. Alright here are the #'s

serv. No. 16183247




That's how it looks on the label?
Thanks for all your help it means alot
If you know which is the part # let me know.
Oh and by the way I bought a preaty nice scan tool that does live data and the engine has missfiring cylinders 2, 4, 6 on and off not all the time.


Jun 22, 2007.
Hi Brian,

16183247 is the number the parts store will need. Napa would probably be my choice of suppliers on this. I think they have a-1 cardone as the manufacturer. Advance auto may also carry the same.
Aside from a-1 cardone, Standard ecms have been pretty good also. You may also have luck out of a junk yard if the cost is unreasonable. I would guess a hundred bucks or so.

Thank you for all the help you have been!


Jun 22, 2007.
Don't thank me until the problem is solved : shock: Before doing anything else, check behind the glove box for blown fuse(s).

After a little looking around, I learned that the first quad driver controls the boost control and purge solenoids and the tcc soleniods. While I have run into a computer issue on these, research is showing that is is more likely a problem on one on these circuits. The fact that the # 3 quad driver is also a problem may indicate 2 problems or more.

The misfires are a concern to me. These had a problem with the intake manifolds and I wonder if there is an internal leak there.

I found the problem with the quad 4 system. The place you told me to look for those fuses, I found the 15amp fuse was blown. Ialso found what caused it. The a/c compressers clutch was locked up an the coil that makes the clutch engage melted togther do to the heat from the bearings and created a dead short. If your wondering the a/c compressor has been bypassed with belt designed for engine without a/c. Also the motor still is running ruff. I spryed starting fluid around intake manifold and vacum lines plus throttlebody found nothing. Then when it was dark I started spraying water around sparkplug wires and the ones that where missfiring on and off, you could see the wires arcing togther all over. I, m going to change plugs and wires tomorrow. I hope this is the only problem. It also serges when throttle is held in one spot do you think those spark plug wires could cause this?

Jun 26, 2007.
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