1993 buick regal limited trouble code 26 and 36 what is a quad driver circuit andwhat are they

The easiest route would be to replace the pcm with a used one. The quad driver circuits are inside the unit. Somebody trained at computer repair could do it, no problem. But just buy a used one for a few bucks, transfer your mem-cal packet (memory and calibration) into it, install it and you are ready to go again.

Before you take out your old one from under the dash passenger side, be sure and take off the negative battery cable from the battery. Never unplug or plug in any connections to the pcm when the battery is on line. Damage may result.

Code 26 is for a problem with one of the quad drivers inside the engine computer, or the wiring harness, and code 42 is for a problem with the ignition module or the control.
You'll need a shop manual with the testing procedures for each code to proceed.

Clean throttle body,fuel filter,air filter.

code 26 is .... Quad Driver Module (QDM A) error

code 26 is .... Quad Driver (QDM) "A" Fault
code 42 is ..... Electronic Spark Timing (EST) Circuit

DTC 26 and 27 refers to a QDM (Quad Driver Module) fault.
The Quad Driver is a "safety valve" for the ECM controlled circuits, the quad driver controls up to 4 circuits.

There are multiple quad drivers in the ECM. The QDM shuts down a shorted circuit to prevent high current flow from damaging the ECM. So the DTC 26 or 27 will isolate the problem to 1 QDM. You will need a repair manual with electrical diagrams and DTC flow charts to determine which of the circuits controlled by that QDM are failing.

Usually DTC 26 refers to the Torque Converter Clutch solenoid and related circuit. Most likely you have a shorted TCC solenoid or the harness connected to it, The solenoid is internal in the transmission accessible from the side cover.

Also, keep in mind the single most cause for any code will be a power or ground problem. Clean all the battery cables, and any and all cables or wires that attach from the engine to the firewall.

Hope this helps; also keep in mind that your feedback is important and I will appreciate your time and consideration if you leave some testimonial comment about this answer.

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The only wiring schematic I could find for your car is for the 2000 Buick Regal, but I hope this helps,
since it gave me a reason why starting a car would cause the driver's power window to
go down, and no other window in the car - it has a special circuit component
(the "Express Down Module").

Its possible that the Express Down Module in the power window switch circuit has failed. This
module latches the "Express Down" switch in the "made" state until released by the "Express
Down Module." If the Express Down Module is latching the Express Down switch when it
shouldn't (at power-up) instead of when it should (at the window "down" limit), then the driver's
window would lower when the driver starts the car. The way to tell if this is the problem is to
note how fast the driver's windows goes down - if it goes down ALL THE WAY, then you know
that the "Express Down" circuit is involved (and therefore suspect the Express Down Module).
If the driver's window only lowers part of the way, then the Express Down circuit is exonerated.
See the various components of the driver's power window circuitry in the
2000 Buick Regal power window circuit schematic below.

The computer has this inside of it,the computer will have to be replaced to solve this problem

Hi! I have enclosed 3 trouble trees for you. The code being stored is a quad driver error. Quad(which means 4)drivers control up to 4 things. They are located in the engine control module. They provide ground for the items that they control. This could mean a component that the driver controls could be bad or the computer itself. Hope this helps you!

The quad driver is in the computer it drives the fuel injecters. you could have an injector problem if one injector shorts it will cause the code to show up you can ohm the injectors and find the problem e-mail me and let me know what you find Phil