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Code 35 IAC problem

This is a discussion on Code 35 IAC problem within the Technical / Maintenance forums, part of the General Discussion category; Hello Everyone, My Truck is a 1994 Yukon GT with the 5.7 liter motor. When the truck idles for a ...

  1. #1
    Registered User xtremexnyc's Avatar
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    Code 35 IAC problem


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    Hello Everyone,

    My Truck is a 1994 Yukon GT with the 5.7 liter motor. When the truck idles for a long period of time I get an SES light. Did the paper clip trick and got a code 35 which pointed to the IAC. I replaced the IAC with a AC Delco part. About one month later I'm getting the same code when idling for a long period of time. Not to sure how to test if the IAC went bad again. Do you think I got a bad part or do I need to troubleshoot further and rule out the IAC since it was replaced. Note that when the SES light comes on the truck still idles fine. When I tap on the throttle in park the light goes away and then about 3 to 5 mins later it appears. Thanks in advance for your help.

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    Re: Code 35 IAC problem

    You might try cleaning and rebuilding the Throttle Body. Kit's don't cost to much.
    Wouldn't hurt to test the IAC either. You can get bad parts out of the box.


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    Registered User xtremexnyc's Avatar
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    Re: Code 35 IAC problem

    Thanks for the help. Anyone know the procdure on how to test the IAC sensor?

    Thanks

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    Re: Code 35 IAC problem

    1995 K2500 Ext Cab 5.7 5spd NV4500(RPO MW3) 4x4 8600GVW, 3.42 rear end, New Edelbrok 3704 Performer TBI Intake, ZOOM 30014 Performance Clutch, 265/75/R16 8 Lug
    2001 GMC 2500HD Ext Cab Long bed, 6.0 Stock, 4L80E, 265/75/R16 8 Lug

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    Registered User xtremexnyc's Avatar
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    Question Re: Code 35 IAC problem

    Sorry to bring up an old post. Still getting the code 35 (IAC Can not set the desired idle speed). Tried another IAC to rule that out. Also replaced the wire harness because the connector cracked. What else can I do? Is there procedure or something that I need to do after a new one is installed? Or do I just screw the sensor in, plug in the harness and go. Much appreciated.

    Thanks

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    Registered User Cheyenne'88's Avatar
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    Re: Code 35 IAC problem

    There's a specific length you're supposed to set it at before you put it in, I think, at least for my year. ('88)
    Did you clean the passageway that it fits into?

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    Registered User xtremexnyc's Avatar
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    Re: Code 35 IAC problem

    Didn't notice much dirt. Cleaned out the passage with some carb cleaner. I think I found the procedure to reset the valve. Do you think it would fix this code? Or should I look some where else.

    Disconnect the battery to clear all of the IAC modifiers from the memory of the ECM.

    Warm engine to opertaing temp.

    Ground the diagnostic link terminal at the ALD connector uner the dash. Ground terminal A to terminal B.

    Turn ignition to run, but don't start engine. Wait at least 10 seconds, and the pintle will drive itself full into the seat in the TB, effectively closing the IAC passageway.

    With the ignition still in run, and the terminals still grounded, disconnect the connector from the IAC itself. Try to pull the connector straight off, and quickly. It is important to break all of the IAC circuits at once, otherwise the pintle may move.

    Remove the ground from the A and B terminals.

    This will have eliminated the IAC from the system.

    Start the engine, and allow it to idle in Park until the idle stabilizes.

    If the idle is not around 700 RPM, adjust the blades with the screw at the front of the throttle body. Remember, this screw has a cover over it from the factory. It uses one of those star bits.


    After the idle is adjusted, turn off the engine and reconnect the IAC connector.

    With the IAC connected, it should produce an idle of around 800 in drive, held with the foot brake.

    If this doesn't produce the desired results, go thru the procedure again
    Last edited by xtremexnyc; 03-20-2009 at 08:42 PM.

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    Re: Code 35 IAC problem

    I have never "adjusted" one.
    However that does not mean that yours does not need to be.
    I wonder if you may not have a leak around the throttle blades or something along those lines. If the gasket on the bottom of the TBI or even the intake is bad it could let "extra" air in like the IAC but not enough to make it act funny, just to throw a code.


    03 Silverado ECSB, Dmax, Allison, 3.73 G80
    96 Silverado ECSB, 350, 4L60E, 3.73's Powertrax Locker
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    Registered User Cheyenne'88's Avatar
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    Re: Code 35 IAC problem

    Quote Originally Posted by kcb37
    I have never "adjusted" one.
    However that does not mean that yours does not need to be.
    I wonder if you may not have a leak around the throttle blades or something along those lines. If the gasket on the bottom of the TBI or even the intake is bad it could let "extra" air in like the IAC but not enough to make it act funny, just to throw a code.
    X2, yeah that's kinda deep. I don't think you ever want to mess with that torx screw, either.
    If you wiggle it a little while pushing it in (just down to 1-1/8"), and you can get it in there without it bottoming out, then start the truck and then shut it off, the ecm will adjust it.

  10. #10
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    Re: Code 35 IAC problem

    The minimum air rate (screw behind the plug in the TBI) is the absolute last resort for fixing an idle problem; it's really for trucks with crazy miles on them that all other attempts at fixing a low idle have failed. I've done a total of one ever, on a TBI that had well over 200K miles.

    The process you mentioned isn't literally for adjusting the IAC, it's a reset. It's a dumb system, the ECM doesn't actually know where the IAC is. It sends it signals to move in or out based on an assumed start position. You can clear/reset this position by...disconnect battery for at least 30 seconds to clear the memory. Reconnect battery. Jump A&B terminals on ALDL connector. Turn key on, wait 30 seconds. Turn key off. Disconnect jumper from A&B terminals.

    You should always do the reset if you ever:
    Replace the IAC
    Accidentally move the IAC pintle AT ALL while you have it out for cleaning
    Turn the key on while the IAC is unplugged

    Richard

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    Registered User xtremexnyc's Avatar
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    Re: Code 35 IAC problem

    I'll try the reset out and see if it helps. After all I did replace the IAC (twice) and the wiring connector. Also will look around for some vac leaks. Thanks all for your help and suggestions. Truck runs fine other wise. Only when it is at warm idle for a long period of time in park I would get the ses light. In park when I tap the throttle a little the ses light goes away then after about a min it comes back.

  12. #12
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    Re: Code 35 IAC problem

    can someone please show me which terminals are the A & B on the aldl connector
    1994 ECSB K1500 F44 Z71, 295/75/16 tires.

  13. #13
    Registered User xtremexnyc's Avatar
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    Re: Code 35 IAC problem

    Jump the two right upper terminals.

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