So I have been the victim of the dreaded IACV killing the ECU. 2001 Max GLE. One night after my son returned home I noticed his car idling high ~1500 and the SES light was on. I pulled out the OBDII scanner and had the dreaded P0505 code. I reset and tried the idle relearn to no avail. Then I purchased a new valve from courtesy. After I installed the new valve, the idle was bouncing between 1500 and 2k. I again tried the idle air relearn and no change. So I pulled the ECU (Had Already smelled the burnt eletronics smell) and confirmed the worst. The STA509A had blown up, one of the legs on the IACV had shorted to the center 12V.

It took out a few traces, but I fixed them and put a fuse on the one driver trace that had evaporated. One of the traces that burnt up was from the driver chip. Luckily at work I have a microscope/soldering station and was able to tack a wire-wrap type wire and connect it to the proper pin. I verified the feedback lines were gtg too.

Now the problem.

When the car is started, it idles AWESOME! But once it warms up, and the accelerator has been depressed, the idle will drop low and it will stall. Again I tried the idle relearn (MANY, MANY, MANY times) but no joy. After it stalls, if I try to restart, it will stall again. BUT if I turn the ignition all of the way off, it will idle fins for a little while again, but not as long as when the car is cold.

Today I brought home an o'scope to watch the signals. I noticed that pins 1 and 10 on the 509A are not ground or 12V. Is this typical? I do have 12V on pins 2 and 5 of the IACV. There are signals on the output pins of the ECU to the IACV( 6, 7 8, 17).

I am at a loss. When the car is turned off, you can hear the IACV resetting. Any hints to help my kid save a few bucks. We took it into a local shop (Non-dealer) and they took 48 bucks and told me it is the ECU.


Any help would be appreciated. I don't mind sending this thing out, I just don't want to hear he need a new ECU. The car was a gift from my parents and I am beginning to regret the gift.

The good new is I will now replace the IACV in my 2003 Max before this happens to me.

 

Just tossing out an idea, but would the current ECU need a re-programming seeing that you have already replaced the IACV? just a thought

I have also read that if you have electronic motor mounts, and are having a problem with the IACV some of the guys have suggested to unplug them as they to can short out the ECU (electronic motor mount also know as the torque mounts) located on the cross member under the engine.

As I said just tossing some idea's into the mix

 

I threw in the towel and sent the ECU to Gino @ Module Repair Pro in LA. Gino wasn't happy I tried to repair it, but he said he would take a look. I received the unit back a few days later and it is working perfectly. I used the Blazt and NDSII to perform the idle air re-learn and all is well with this max once again.

Lesson learned. I just bought a replacement IACV-AAC for my wife's 2003, so I do not have to go through this again.

 

I wasn't aware 02-03's had this part due to the e-throttle.