Does anyone know of a site with a documentary of these 1993 PCMS?

 

Here's some info I found... hope this helps.

26 Quad Driver Module Numer1 Check EGR, Canister Purge and AIR pump relays with a digital Ohm meter. A resistance of less than 18 ohms indicates a bad relay. If OK, potential ECM failure.
27 Quad Driver Module Numer2 Potential ECM or on a manual transmission car, potential upshift relay problem. Check relay, replace if less than 18 Ohms using a digital Ohm Meter.

 

By the way, this info is for Vettes, but the same should apply on F-bodies as well since the ECM has the same part number. (the memcal aka memory/calibration module is a little different though)

So the quad 2 could be some TCC problem or maybe some parts went bad in the ECM...

 

Hey Madwolf,


Code 26: As far as this is concerned, I eliminated by Air Pump. I have taken off the EGR module, and blocked off all holes in back of the intake manifold. The connections for the Air Pump, and the EGR just hand there.

As for the canister purge, I have not checked that, but I eliminated the vaccum tube that goes into the intake manifold just yesterday (forgot to mention that). With that I also eliminated that module that is on the passenger side where this hose connects. Again the connection just sits there. I plugged all the holes to the TB.

Code 27: I have noticed that at times (almost never) the scan tool will see this driver as being bad, for a second or so. I do not have a manual transmission.

Does anyone have insight as why a cylinder (2) would not get as hot as the others?

thanks for yor help guys.

 

Maybe it wasn't giving enough fuel in number two cylinder or it could be a spark plug that isnt sparking properly that could result not being heated fast enough....

just my 2 cents

 

oh sh*t that happened to me today out of no where, my car overheated and then code was on after i turned on the car, i got back to the shop where i work at and put the scanner on and code26
code 27
fan 1 fault

all of these where on i tryed clearing the codes and the fan fault cleared but not code 26,27 which i am aware of being qdm, can it be the fan fuse that went out which i'm about to check in a few moments after reading this post.?

 

Do you still have the wiring in place for the AIR pump etc? If so, check to see if any of it is shorted. On a friends car, the QDM was toasted by a shorted EGR coil. The pcm had to be replaced.
Hope this helps.............

 

i checked every fuse and found out my fan fuse was blown so i replaced and problem fixed, i do want to suggest something though check your fuses with a test light not just by looking at them i find that very helpful you will be surprised, good luck with your problem. laterz

 

Update,,,

I removed the pcm4less chip, to try to run the car without custom programming. And alas, it threw code 26 Quad Module 1 Failure, and immediately started my fans. The car ran like crap like this, it puffed black smoke at idle way rich. It barely idle too.

I also noticed that Quad Module 2 failed intermittenly only when in gear. (Reverse or Drive).

I have read that Quad Drivers are inside the ecm, and a failure in them means the ecm is toast. And immediately runs on back-up on get this (limp home mode).

If a code sets of your fans, that means it is in limp home mode right?

It does not specify what this drivers runs, but it is the only means for the ecm to send out information to control the engine.

Thanks

 

The quad drivers are nothing more than a series of grounds in the ECM that are used to control mostly emmisions related circuits. Since you have removed a lot of the emmisions stuff, it is possible the codes are being caused by this.. If you replace the ECM and it does not fix the problem, then you will have to look at every component on that circuit and the wiring.

 

UPDATE:

I played around with the car yesterday, turned it on and began to disconnect the injector harnesses. I did not notice any change in idle. WHY???? I radomly took out injectors, and nothing seemed to change, unless I took out 2 at a time, where I could notice a significant drop off in idle. But nothing too noticable.

I am playing with the possibiliby that my injectors are open all them time with the ignition on. Can they possibly be grounded and therefore open all the time? How can I check.

Also, I will be ordering a new pcm from GMPARTSdirect for $90, and possibly a new engine wire harness from Painless, while i send my chip back to program out my VATS function.

Also FASTTRACKPErFORMANCE.com has a new harness that allows either a Accel DFI or Speed Pro ECM to piggy back on to the stock ECM and overide it. It comes in a package along with programming software. do not know the price. Has anyone heard of this. I am told that we retain the stock wiring harness.

thanks