can someone help me out and explain what could be wrong. let me know how to fix it.

 

Same with my car. Did anyone ever help you out, or did you figure it out? I would like to fix it because it comes on immediately now when i start it and it turns the fans on too, so the car never warms up. I would like to get it figured out...

 

Is your car a '93 also? Some '93 codes are different than other years...

www.fastbird93.com/Diagnostics.htm

 

Yeah mine is a '93 too. I've looked at that site under DTC 26, I'm just not exactly sure what it means. It sounds electrical and I'm not a real big electrical guy so far when it come to cars. Any ideas what I should check? It seems to have been getting slowly worse too, because when I first got it (beginning of this year) it had no engine light at all, and then it slowly started coming on more and more often, and now it's on right when I turn it on most of the time.

 

bump. Anybody have anything on this?

 

Here's some copy\paste

CODE 26 - QUAD-DRIVER NO. 1 ERROR ECM controls most components with electronic switches completing a ground circuit when actuated. Switches are arranged in groups of 4, called Quad-Driver Modules (QDMs), which can independently control up to 4 outputs (control module terminals). When an output is actuated, terminal is grounded and its voltage normally will be low. When an output is off, its terminal voltage will normally be high. QDMs are fault-protected. If a relay or solenoid coil is shorted (having very low resistance) or if control side of circuit is shorted to voltage, too much current would be allowed into QDM. QDM senses this and turns driver off or QDM's internal resistance increases to limit current flow and protect QDM. Result is high output terminal voltage when it should be low. If circuit from battery voltage or component is open or control side of circuit is shorted to ground, terminal voltage will be low, even when output is turned off. Either of these conditions is considered to be a QDM fault. Each QDM has a separate fault line to indicate presence of a current fault to control module central processor.
scan tester displays status of each of these fault lines as "low equals okay" or "high equals fault". 1. Code 26 will set if the ECM detects the wrong voltage potential for 20 seconds. This test will begin to determine if the QDM-connected air pump relay can be controlled by the ECM. If the relay appears to operate but the air pump does not turn, diagnose mechanical/electrical portions of air pump. 2. This check can detect a partially shorted coil which would cause excessive current flow. Excessive current flow to a QDM will be detected as a fault and set a code. 3. The remaining checks will identify a circuit problem that has caused an excessive current flow or inoperative relay. If a QDM circuit check is done on a relay, it is important to identify and test the relay coil terminals of the harness connector to avoid improper diagnosis. See DRIVE CIRCUIT TEST in CODE 28, QUAD DRIVER NO. 3 ERROR. Diagnostic Aids Engine should be idling while monitoring QDM status. Using scan tester, monitor QDM status while moving related harness connectors, including ECM harness. If the failure is induced, a fault will status while moving related harness connectors, including ECM harness. If the failure is induced, a fault will appear on scan tester. This can help to isolate intermittent problems. If code persists with no apparent problems, replace ECM. NOTE: Test numbers refer to numbers on diagnostic chart. 1993 Chevrolet Camaro Z28 G - TESTS W/CODES - 5.7L 1993 ENGINE PERFORMANCE General Motors Self-Diagnostics - 5.7L "F" Body ECM/PCM 1993 Chevrolet Camaro Z28 G - TESTS W/CODES - 5.7L 1993 ENGINE PERFORMANCE General Motors Self-Diagnostics - 5.7L "F" Body ECM/PCM


See P.D.F.

 

Ok, thanks. I'm still really confused about all this. I haven't done much with electrical stuff before.

I've eliminated the AIR pump as the source of the code by unplugging it and having the light still come on. Then I pulled the two little tubes off of the EVAP purge solenoid and saw some nasty crispy black stuff (maybe even charcoal?) in there where the tubes connect and tried cleaning it out by spinning a little drill bit in there and blowing some compressed air in after that. As far as I could see it cleaned it out pretty well, but there may be more in there deeper. Either way, it's still giving me the light. I looked up that part and an AC Delco replacement is only ~$22. Should I try replacing it, or am I reading all the stuff wrong and replacing it couldn't really help any?

 

As far as the charcoal in it, or the vacuum ports plugged up, it has no bearing on a quad driver fault. And unplugging the air pump doesnt take that out of the equation. The computer is activating a coil in the relay. Not the actual air pump. If you have anything disconnected like the EGR solenoid, the purge solenoid, the air pump relay, these will all set a code 26. If they are shorted or open, they will set a code. Unplugging them wont make the code go away, it will make the code set.

 

Oh... hehe . I guy in my car club told me to unplug it to make it go away, so when I unplugged it and the light still came on then I thought it wasn't that. So sorry for sounding dumb.... lol

I don't really know how to go about fixing this now.... except taking it to the dealer and saying "fix". lol

Edit: The reason this is really annoying me is because I'm not driving it while it's doing this .

 

start with this:
if the fans run the fuse is good for evap and egr. check for continuity between A and B
terminals on both solenoinds. and 5v at the pwer side KOEO.
check fuse #7 air pump and continuity on the relay coil 86 & 85. the power is jumpered
on the relay (same for points and coil) locked up air pump fairly likely.
unlike OBD2 which would give you a specific code for a certain circut, there are three to check. with the schematics and a DVOM you should be able to run it down though a process of elimination.

 

Solenoids are not powered by 5 volts. They are powered by 12 volts. The 5 volt circuit is for sensors, not actuators.

 

Is it possible that my EVAP Purge Solenoid is bad? I heard from somewhere there should be an audible ticking from it while the car is running, but I can't hear a thing coming from mine. I can get right down by it and don't hear anything. I touched it too and don't feel anything at all.

 

Anybody know? I bought a new EVAP solenoid and I can just go put it in if you think that might solve the problem, but I don't want to if there's no chance that could be it. What do you think?

 

Ok, it's not the EVAP solenoid, I checked that.

I did find a blown fuse #7 (AIR pump fuse), so I was happy to begin with. After that I replaced it and then ran it for a few minutes and again I got the code, so I checked the fuse, and it was blown again. Does that mean I have a bad AIR pump that needs to be replaced?

Also, the last couple times I've run the car I've had a DTC 34 (MAP sensor signal (voltage) low/vacuum high) too. This time I tried revving it up a little and it won't go above 3k rpm... Would that be related to the code? What would you suggest to fix that? Do I just need to replace the MAP?

 

Alright guys, time to bring back an old thread. Sorry. Lol. I never fixed it though. I did get the DTC 34 to go away by replacing the MAP, and it runs great now, but the DTC 26 is still there and annoying me. Especially considering I'm getting ready to sell it and I'm sure people wouldn't look to great on an engine light even if it isn't something serious .

I don't think I ever got an answer to the AIR pump blowing fuses question. Could that be something?