I have a 1993 Z28 and last year, after 180,000 miles on the originaly engine, the SES (Svc Engine Soon) light came on. I checked the code and it was "Quad Driver Module 26."
I also had problems with the AIR pump blowing fuses constantly, so I replaced the AIR pump adn oxygen senors. The car ran a LOT better, but about a few weeks later, the SES came back on with the same code.
I have since blown a head gasket and put a new engine (383!!) in with new fuel injectors, new OptiSpark, new oxygen sensors, new cat... New water pump too. It's back to running and seems to be running right, but that light is still on and I'm getting the same code.
I've checked many forums on the web and they advise several different things, but I've changed most everything, EXCEPT the ECM and many say they don't think that's the problem. I don't want to spend the $$$ for that just to find out it wasn't the problem.
Can anyone suggest what to check and/or do next? I'm about to have someone do a custom chip for this (it's speed density, no MAF), but they don't think that will solve the problem and if it's in limp mode, will the chip help with the performance at all? I want the chip for the new cam, not to resolve the QDM issue.
HELP!

 

Are you getting DTC 26? Quad Driver Module 26 is not defined as a trouble code. DTC 26 refers to the EVAP system purge solenoid. Quad driver usually refers to the EGR.

Craby has a 93 FSM, and he may have better info.

 

Just had the 26 code on the wifes low mile 93 z. Turned out to be a blown #7 fuse (air pump) . Disassembled it-full of water and seized up . I plugged the inlet and outlet also cut the wires off in side and reinstalled it. It looks totally stock under the hood and the engine seems to run just fine. No codes ! Ill keep a look out for a reasonable priced replacement . The shop I use for major issues said the air pump only aids in bringing the converter up to temp faster . Is that it's only or major use?---Bob

 

Back from the dead after 3 years. lol

 

Sorry-Just found this site. Does that mean I get a prize ? Working on the wifes 93 z. We're the original owners-just put 20 year classic plates on it-50339 miles-never seen snow -no dings -no rust-still clean underneath . It's stored over the winters (this year almost 8 Minnesota months worth). When we took it out of storage this year the battery when installed took a crap also it threw dtc26 plus one wheel sensor died. Is there going to be a problem leaving the air pump disabled ?---Bob

 

no, my air pump was toast for about a year. didnt even throw a code.