this seems to be a common problem, from V6 to V8, there's a lot of posts on it, but nothing definite.

who's got all the data, and fixed this?
or do i just buy LT1 EDIT and delete it?

 

Here's a cut & paste of all the decent info i found in other threads:
remember it's a 93 problem, but this one 94 guy had some info.

http://home.comcast.net/~fastbird/Tr...Aids/dtc26.jpg


I changed my PROM when I did my heads/cam, but my QDM failure code stayed in the computer. It didn't go away until I changed the main ECM

It's tough to find information on because it's gone in 94.. but I think it includes air and egr and fuel vapor solenoid and one other thing.. then again there might be two quad drivers modules.. i dunno. Do a search or check out www.speeddensity.org .. I was having a problem and just programmed the code out because I was tired of seeing it and don't have any emmisions on the car anymore.


http://web.camaross.com/forums/showt...highlight=quad

http://web.camaross.com/forums/showt...highlight=quad

http://web.camaross.com/forums/showt...highlight=quad

http://web.camaross.com/forums/showt...highlight=quad

http://web.camaross.com/forums/showt...highlight=quad

http://web.camaross.com/forums/showt...highlight=quad

http://web.camaross.com/forums/showt...highlight=quad


hey there, i have posted a few times, about the same situation, but i have gotten alittle farther in my research, and i found out my bucking problem is due to a bad quad driver. i have replaced the computer once already and its throughing the same code with is 26 quad driver 1 non working. i called the dealership and they said its a faulty computer. its brand new. why am i having such bad computer problems? please help??

It sounds as if you have a wiring problem at your injectors if I'm understanding it right. Check to see if they are all plugged in and there is no chafing. The computer will turn off a pair of cylinders if it monitors an open or short in the circuit. A scan tool should tell you what cylinders are now misfiring which should help you track it down.

The Quad driver is not the injector driver. Its a module in the ECM (93 and earlier) that drives the high current loads like solenoids. DTC 26 is for Quad Driver #1, and covers these three items, from Shoebox's online code list for the 93:
Quote:
Quad-Driver Module (QDM) #1 circuit
applies to:
- AIR pump relay circuit
- EGR solenoid
- EVAP solenoid


You need to check each of those devices for a problem, and check the QD Module. Possibly the relay or a solenoid is faulty, or they have an electrical problem that is damaging the driver.

In OBD-I, there is no misfire detection. His 93 has only two injector drivers, and they each control 4 injectors on one bank.

With the AIR pump, you just unplug the harness connector from the pump, and make sure the fuse in the circuit is good. There will be no code AFAIK.

The fact that the EGR solenoid is plugged won't set that code. The code is for an electrical circuit problem. Hard to understand how the EGR solenoid could get plugged up. The EGR valve can plug up, but not the solenoid. Are you sure you don't mean the EEC (EVAP) purge solenoid is getting plugged up? That one WILL plug up when the charcoal in the vent canister breaks down and the small particles get sucked through the purge system.



If so, what were the specific codes? The "quad driver" module was used in the 3rd Gen ECM's, and in the 1993 4th Gen ECM to control the high current loads like solenoids, etc, that couldn't be driven directly by the ECM. But I have the 93-95 V6's in my Chilton's and it doesn't list any "quad driver" related codes. Perhaps the problem is the list that came with the Actron.... often they are manufacturer "generic" rather than year/model specific.

Yes this is on the 94 v6. I kinda assumed that the actron was the "radio shack" version anyways. my specific codes, i'm thinking my 24x code is a 36? and my egr codes are in the 70's they're fairly common i've heard for this engine. The egr consists of 3 fairly large solenoids, so what you said about the QD's doing the heavy solenoid work, may hold true to this egr thing. Oh and the Egr valve and crankposition sensor are brand new. Allinthered on the v6 specific board had mentioned he cleaned the silver conduit looking pipe that goes from the egr to the intake manifold and that solved his problem, but it hasn't workd for me.

Which of the quad drivers shows as failed? #1, #2, #3?
I am not sure about #3, but I know a faulty/removed air pump or EGR will cause #1 and #2 to fail.

69 camaro with a 94 LT1/T56 swap. I recently started it up and a few codes were thrown. The only one that is concerning me is the "DTC 26: Quad Driver Module1 Fault" The fans kick on immediatly which to me suggests that it is in what is known as "limp home mode." What exactly is the quad driver code? I had the harness modified to remove the air, egr, evap and the PCM is STOCK (no programming yet at all). I called the wiring place and they say my PCM is bad. I called Bryan at PCMforless to get a second opinion on that and he concurs. I spoke with my buddy about it (he's an early GM FI EXPERT) he says he just doesn't think the PCM is bad. While doing testing for me on his TPI car he pulled the plug for the EGR and it threw a "quad driver moduleA fault" is it possible that the computer is still searching for the EGR or another sensor on the same quad driver and isn't finding it and throwing the code? Trying to do a little research so i dont drop 100-150 on a new pcm and have the problem still exist.


When you removed the "evap" system, the PCM no longer sees the correct voltage when it attempts to ground the evap purge solenoid. You would have to put the correct resistor into the wiring harness, in place of the missing solenoid. You will get the same problem for the missing EGR solenoid (DTC 27), and if you didn't wire up the AIR pump relay and insure a good fuse in the circuit (DTC 29). Or, you need to have your PCM programmed to delete the diagnostics.

When you need to look up a code, use Shoebox's list... it shows the differences between the 93 and the later LT1 cars.

http://shbox.com/1/Dtcs.htm
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The diagnostic for the EVAP purge solenoid is looking for near "0" voltage when the PCM supplies the ground to activate the solenoid. The purge solenoid is 35.4 ohms resistance. You could get away with a much larger resistor, to keep the "watts" requirement of the resistor to a minimum. On the skip shift solenoid (12.4 ohms) people are generally able to get away with a 2,000 ohm resistor. The diagnostic for the skip shift solenoid is similar to all the others - looking for near (but not equal to) "0" volts at the PCM when the device is activated.

I doubt the PCM does very much in the way of "protection" on DCT 26. There is no inherent risk of damage to any component of the vehicle if you lose the purge stream. The PCM will turn on the fans for DTC 29 but I don't think it takes any other protective action. Not sure why it even turns the fan on.

 

Before you go tryin to program it out, check your airpump fuse. Thats what mine was. I made the SES go away fro .77 cents, no programming needed.