Quad Drivers, IAC, and EGR.
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Joined: Oct 2011
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Quad Drivers, IAC, and EGR.
Well, I have a 3.4L V6.
High Idle after warming up (1.5k), as well as EGR codes 75, 76, 77 (1, 2, 3). Quad Drivers 1,2,4 are bad (even though the car doesn't use 4).
Replaced IAC and recalibrated it. IAC Count is at 0 on idle, reaches 50+ when gas pedal is used.
Replaced EGR and Connecter. Not help.
I'd like to see if it could be anything else before I replace the ECM and get it reflashed to see IF that could be the issue.
Thanks.
High Idle after warming up (1.5k), as well as EGR codes 75, 76, 77 (1, 2, 3). Quad Drivers 1,2,4 are bad (even though the car doesn't use 4).
Replaced IAC and recalibrated it. IAC Count is at 0 on idle, reaches 50+ when gas pedal is used.
Replaced EGR and Connecter. Not help.
I'd like to see if it could be anything else before I replace the ECM and get it reflashed to see IF that could be the issue.
Thanks.
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IAC count of zero means its completely closed. Where is the air coming from? Did you try plugging the IAC port to see if the car stalls.
If car stalls when you plug the port, air is passing the IAC while it has a count of zero it is either not taught right, a bad IAC or you have a bad ECM. Oh and that would be the quad driver that was failing to drive the IAC.
If the car does not stall when you plug the IAC port then your getting air from some place else.
If car stalls when you plug the port, air is passing the IAC while it has a count of zero it is either not taught right, a bad IAC or you have a bad ECM. Oh and that would be the quad driver that was failing to drive the IAC.
If the car does not stall when you plug the IAC port then your getting air from some place else.
Overdrive Member
Joined: Apr 2010
Posts: 3,354
From: Spanaway, WA
In my years of playing with computer controlled vehicles once you get a quad driver issue it is 90% of the time the PCM and the other 10% bad wiring causing the driver's signal to be sent to ground. To know for sure unplug the device the driver operates then check the line for resistance to ground. It should be open but if you read anything other than open you have a short somewhere. If all reads open chances are the drivers are dead in the PCM
Massey
Massey
2nd Gear member
Joined: Aug 2013
Posts: 509
The quad-driver Malfunction flags for 93 and later engines are notoriously inaccurate, so much so that GM stopped using them on their scan tools. Concentrate on the EGR trouble codes, knowing that any fault with the vacuum system (MAP sensor for example) can trigger those codes as well as an ineffective EGR valve.
Thread Starter
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Newbie
Joined: Oct 2011
Posts: 23
The quad-driver Malfunction flags for 93 and later engines are notoriously inaccurate, so much so that GM stopped using them on their scan tools. Concentrate on the EGR trouble codes, knowing that any fault with the vacuum system (MAP sensor for example) can trigger those codes as well as an ineffective EGR valve.
Previous owner must have adjusted the idle intake screw, the one that you need to hold the pedal down to reach. After backing the screw off, car idles perfectly with no issues. I've went ahead and ordered a new pcm for $70, and put that in. I've yet to see the EgR issue I was having. Thanks for all the help.
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