Quad driver diag code on 93 lt1 - Team Camaro Tech
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post #1 of 5 (permalink) Old Feb 3rd, 07, 04:17 PM Thread Starter
 
Join Date: Aug 2006
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Quad driver diag code on 93 lt1

I have recently been getting a check engine light on my 93 lt1 transam. I had an auto supply house put a computer diagnositc unit on it and the error code shows faulty quad driver. Also after starting the car the following happens: The car starts and about 15 seconds later the check engine light comes on and also both cooling fans start up. The car seems to run ok still but this cant be good. Has anybody out there seen this problem? Thanks in advance Jerry

1969 Rally Sport
1968 327 w/camel hump 64cc 202 heads
Turbo 350 308 posi multi leaf
(soon to be 700r4)
Finally got my dream car....
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post #2 of 5 (permalink) Old Feb 3rd, 07, 05:23 PM
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Mark
 
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Re: Quad driver diag code on 93 lt1

Quad drivers (QD) are integrated circuits inside the ECM that it uses to close or open the circuit path to ground, turning a device on or off (like your fans). Most quad driver circuit faults are due to a short in a device or its circuit. (Wiring/connectors). However at times a device or circuit that is open will set a quad driver fault code. Each quad driver can control up to four devices. So circuit diagrams will have to be used to find which devices the quad driver at fault is controlling.

A normally operating device and its circuit will have at least 20 ohms of resistance and can be checked with an ohmmeter. This will tell if the circuit or device is open however, this will not place the device in operation. So if the device is only failing due to heat after being in use for a period of time the fault will not be found with a resistance test.

If the vehicle is early gm and has a constant check engine light with a quad driver fault code set the computer (ECM) may have became permanently damaged. But if the ECM is replaced without any diagnosis to locate and repair the cause of the fault then the new ECM may soon become permanently damaged as well. On newer vehicles with an ECM that has protected quad drivers replacing the ECM is most often not necessary.

Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11

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post #3 of 5 (permalink) Old Feb 3rd, 07, 08:04 PM Thread Starter
 
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Re: Quad driver diag code on 93 lt1

Is there any diagnostic machines out there that would pin point this fault or the device causing the fault? Or is this going to be more of a hit and miss testing a bunch of different sensors and devices. Are faults like this hard to find? I wonder if the fans are a clue maybe a temperature sensor or ??

1969 Rally Sport
1968 327 w/camel hump 64cc 202 heads
Turbo 350 308 posi multi leaf
(soon to be 700r4)
Finally got my dream car....
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post #4 of 5 (permalink) Old Feb 13th, 07, 04:43 PM
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bill
 
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Re: Quad driver diag code on 93 lt1

need the code number not description since theres alot of quad driver modules for engine and also for transmission.
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post #5 of 5 (permalink) Old Feb 13th, 07, 06:51 PM
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george
 
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Re: Quad driver diag code on 93 lt1

Quote:
Originally Posted by Jerry Queen View Post
Is there any diagnostic machines out there that would pin point this fault or the device causing the fault? Or is this going to be more of a hit and miss testing a bunch of different sensors and devices. Are faults like this hard to find? I wonder if the fans are a clue maybe a temperature sensor or ??
Quad driver 1 2 3 or 4?Once you know this you can isolate devices and test accordingly.The coolant fan mode is only defaulting for fail safe.Not a good indicator for accurate diagnosis as this is a norm.Get us the actual DTC.
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