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Thread: 1993 Grand Am Code 26 Quad Driver

  1. #1
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    Question 1993 Grand Am Code 26 Quad Driver

    1993 Pontiac Grand Am SE V6 3.3L mileage: 157,000 Transmission: Automatic

    Code 26 Set For Quad Driver In History-4-5
    I took my car to the dealership they found my service engine light comes on due to the fact i got problem with it by the Quad Driver. My question is what is the quad driver & is bad to run the car as the SEL light is coming on? Can i do this job myself & save $$$. If i can how would i go about doing this job myself. Does anyone know? I couldn't seem to find this in my manual.

  2. #2
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    Erica28 - In the ECM the Quad-Driver Modules (QDM) are used to control several components at the same time. Such as EVAP, Cooling fan, TCC sol. and gauges. Each QDM has a sense line and a fault line. When a component is commanded "ON" the voltage potential on the sense line is low and when the component is comanded "OFF", the voltage potential on the sense line is high. If the ECM detects the wrong voltage the fault line will turn the Service Enigine Soon light on.
    Contact us at [EMAIL="research@haynes.com"]research@haynes.com[/EMAIL] and we can provide a more detailed information, make sure you have your Haynes manual when we contact you.

  3. #3
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    i am having this same problem on my 1993 grand am 4 dr 3.3L it has 216k on it, and i just recently had engine troubles, when i accelerate with the car in gear it bogs down and pops. when i hooked it up to a code scanner it said code 26 QDM error. ii dont know where the QDM is or what would trigger that code, if you could help me out it would be great

  4. #4
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    Hi Charlie,

    The quad-driver module is part of the internal circuitry of the ECM. It controls the operation of the EVAP purge solenoid, the cooling fan relay, the Service Engine Soon light, the torque converter clutch solenoid and the instrument cluster. The problem could lie in the ECM or any of the circuits/components that the quad driver module controls. Unfortunately, for this reason it can be a tricky problem to diagnose (and the diagnostic procedures are quite involved). Start by tracing the circuits for the above mentioned components and look for open- or short-circuit conditions.

  5. #5
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    i checked the circuits on my fuse panel inside the car. All of them work except the one labled INST LPS and another fuse does not work. i tested the actual tabs where the fuse goes in and only one of the contacts was reading 12 v, the other side was reading nothing, and for the other fuse i cant rember what it was called but that one tested no voltage on either side. im not sure if this has anything to do with it but figured i d let you know, what other parts could i replace to try to fix this problem?

  6. #6
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    Charlie,

    Unfortunately, it really isn't possible for use to diagnose problems from a remote location, and as we stated before, this can be a difficult one to track down.

    As far as your fuse block goes, when you pull a fuse out and check for voltage at the terminals, you WILL only get a voltage reading on one terminal; the fuse is what conducts electricity to the other terminal. If the circuit is overloaded, the fuse blows.

  7. #7
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    some one on a differnet forum suggested the PRNDL
    switch is causing the codes, is this a possibility? should i try replacing the PRNDL switch?

  8. #8
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    Well, the PRNDL switch doesn't appear on the circuit diagram, and no mention of it is made in any of the troubleshooting steps in the factory service manual.

  9. #9
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    Quote Originally Posted by admin View Post
    Well, the PRNDL switch doesn't appear on the circuit diagram, and no mention of it is made in any of the troubleshooting steps in the factory service manual.

    theres also a code for a prndl switch error, so i doubt tahts what it is

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