I have a 97 4.2L V-6 that is popping a P1506 error code. I was told that it was my IAC, so I was planning on cleaning/replacing it today. Does anyone here have any other suggestions or have experienced this in the past? I have to get the truck smogged at the end of next month. Thanks for the help.
Do the following; with engine at idle, disconnect the IAC plug.
If idle drops the IAC is good but may need cleaning.
If no change, clean it in an effort to clear a stuck condition from age and gum/dirt.
The test is to get you to see what it is supposed to do and that is control air bypass so idle speed can be controlled within specified limits.
The 1506 is telling you the idle is out of limits.
Thanks Bluegrass7, I did what you said and the idle seemed to drop 100-200 rpms when disconnected. I removed the IAC and cleaned it then reinstalled it and the idle showed improvement. I'll drive it this week to see if the engine code stays away. If that doesn't work I bought a new IAC as a backup. I'll post the results.
To expand on this, the PCM needs to relearn the normal operation because it has tried to account for poor operation and may have shifted fuel and timing tables to some degree..
A way to get it to adust in is the following:
If you start from a reboot, cold start the motor with the lights on and fan on high.
This is about the worst case load the motor will see and use the IAC to control the idle load along with the alternator recharging the battery.
After warm up drive about 5 miles.
Shut off the motor and restart as a hot restart under Alternator load again and use the fan/ A/C as well.
Do this several more times at different intervals and the relearn is about complete for all conditions.
After this, all starts should be well controlled unless there is still another issue.
After cleaning the IAC and clearing the code I drove the truck about 13 miles before the P1506 code came back. I have replaced the IAC, cleared the code and have driven about 5 miles so far. I also checked the monitors and my catalytic and evap show not ready. I was told I have to drive around 50 miles for these to reset. If the IAC doesn't fix this what is my next step?
There are 7 monitors that keep track of system tests.
Some of those tests take a considerable amount of drive cycles to complete.
The Evap system is quite involved so can take some time.
Reason they take various amounts of drive cycle time is the testing is done under many conditions that you may not present during your driving.
So the 50 mile answer is not always the last word.
Until 'all' the monitors are reset you will see a code 1000.
This code is only related to the monitors and not a direct trouble indicator as is has no discription like fault codes have.