DTC 26 help
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Instructor
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From: NH
DTC 26 help
I have DTC 26 popping up on my 93 LT1 Coupe. The FSM tells you to use the Tech 1 in step 1 of the chart to activate the Airpump, Air bypass valve, EGR solenoid, and EVAP solenoid. Is there a way to simulate this? How else can I test these items? Should I just skip that step and measure current to ECM in step 2?
Safety Car
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From: FL
In my experience Quad Driver Module circuit #1 fault codes are often caused by a bad EGR or Canister Purge Solenoids. The purge solenoid is located under the fuel rail cover on the passenger side, the EGR solenoid is under the cover on the drivers side. A simple test is to disconnect the two wire electrical connector at each part then measure resistance across the two prongs of the solenoid with a digital multimeter.
If you see ANY resistance the solenoid is probably okay, bad ones I've found are always open. (infinite resistance, no continuity)
Give that a try first, if the solenoids check out okay post your results and I will try to help with further diagnosis, good luck.
If you see ANY resistance the solenoid is probably okay, bad ones I've found are always open. (infinite resistance, no continuity)
Give that a try first, if the solenoids check out okay post your results and I will try to help with further diagnosis, good luck.
Thread Starter
Instructor
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From: NH
I measured all the solenoids with the following results. EGR=36ohm, Canister=26ohm, AIR bypass=34ohm. With the car running, I am not getting 12V out of the AIR pump relay on the side that should be powering the pump. 12V ign to the relay is OK (thats where I tap my power to exercise the electric water pump relay)
A little more info that I probably should have put in earlier, this car has had the AIR system and EGR deleted by a PO. The solenoid/relays are still in there to fool the ECM into thinking everything is OK. This configuration has kept the light out (except when the ECM tries to exercise the EGR at cruise, different DTC) for over the year and a half I have owned it.
A little more info that I probably should have put in earlier, this car has had the AIR system and EGR deleted by a PO. The solenoid/relays are still in there to fool the ECM into thinking everything is OK. This configuration has kept the light out (except when the ECM tries to exercise the EGR at cruise, different DTC) for over the year and a half I have owned it.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
I measured all the solenoids with the following results. EGR=36ohm, Canister=26ohm, AIR bypass=34ohm. With the car running, I am not getting 12V out of the AIR pump relay on the side that should be powering the pump. 12V ign to the relay is OK (thats where I tap my power to exercise the electric water pump relay)
A little more info that I probably should have put in earlier, this car has had the AIR system and EGR deleted by a PO. The solenoid/relays are still in there to fool the ECM into thinking everything is OK. This configuration has kept the light out (except when the ECM tries to exercise the EGR at cruise, different DTC) for over the year and a half I have owned it.
A little more info that I probably should have put in earlier, this car has had the AIR system and EGR deleted by a PO. The solenoid/relays are still in there to fool the ECM into thinking everything is OK. This configuration has kept the light out (except when the ECM tries to exercise the EGR at cruise, different DTC) for over the year and a half I have owned it.
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Instructor
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From: NH
I checked it pretty much immediately after, certainly within 2 minutes and kept checking it for a while because I couldnt remember the timing. SES light came on and the fans kicked on during the check too. Any other way to confirm the relay?
Safety Car
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From: FL
Verify that you have 12 volts on the red and pink/black wires at the relay, the ECM activates it by grounding terminal F (brown wire) you can do the same with a jumper wire. It the relay closes by grounding terminal F, check the brown wire for continuity back to the ECM. If the wire is good the ECM may be bad.
Thread Starter
Instructor
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From: NH
Relay circuit checked out, so I tried the same thing out on the 3 solenoids (not wanting to throw $300 at a new ECM) I can hear two of the 3 solenoids activating, so I am thinking the AIR bypass solenoid may be the problem as nothing happened when I put the 12V across it. Going to go pick one up at the store and try it out.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Relay circuit checked out, so I tried the same thing out on the 3 solenoids (not wanting to throw $300 at a new ECM) I can hear two of the 3 solenoids activating, so I am thinking the AIR bypass solenoid may be the problem as nothing happened when I put the 12V across it. Going to go pick one up at the store and try it out.
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Thread Starter
Instructor
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From: NH
Yea, jumped one hurdle. Now I have to find the part. Struck out at Autozone and Advance Auto. Pulled the P/N off the part and Delco Remy online says its obsolete. Will have to keep looking or rig up a resistor and try to fool the ECM.
Safety Car
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From: FL
Thread Starter
Instructor
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From: NH
Rock Auto says its not there. Are you thinking the AIR injection diverter valve? Thats all the was showing up at the auto parts store, but it doesnt look right. I can't imagine what I need being any more pricey than the EGR or canister solenoids, it looks similar.
Its Delco Remy PN 17082437 http://catalog.remyinc.com/Product/Details/17082437
Its Delco Remy PN 17082437 http://catalog.remyinc.com/Product/Details/17082437
Thread Starter
Instructor
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From: NH
Not sure whats going on, but I put in a different relay that I had hanging around and just hooked up the solenoid back in and no code yesterday or today so I guess it was the relay after all, old one must have just worked OK in my test setup directly off the battery, but maybe the current was out of spec at the ECM or something. Oh well, its working so I am happy!
Safety Car
Joined: Jun 2006
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From: FL
Not sure whats going on, but I put in a different relay that I had hanging around and just hooked up the solenoid back in and no code yesterday or today so I guess it was the relay after all, old one must have just worked OK in my test setup directly off the battery, but maybe the current was out of spec at the ECM or something. Oh well, its working so I am happy!
I'm never to proud to accept an assist from luck! Glad the relay took care of it.