So I hooked up a light between the negative battery cable and negative battery post. I was draining batteries in 4-5 days! With everything turned off the light was illuminated until I unplugged the IAC valve connector, then light went out, (indicating no more open circuit and no more battery drain). I ordered a new AC Delco IAC which I installed and once I connected the connector to it the light illuminated indicating open circuit again?

I checked for trouble codes through the ecm, no codes just 12. I currently have a hypertech chip in it and as far as I know, it is the stock ECM.

Where do I check from this point on? What else is there that could be causing this open circuit if not for the ECM itself?

 

Just an update and a bump so that hopefully somebody see's this and can give me some advice. I checked the visible areas of the wires coming from the IAC connector and they looked like they were in good shape. I pulled my ECM out and saw that it appears to be a re-manufactured ECM and does not have a brand name on it. It looks old though. I copied down the following numbers which were on a sticker:
Number 7-7165, Calibration code 0798IG, 07716500982120111 REMFG.

Is it possible for an ECM to be supplying a constant signal to say the IAC valve meaning that the ECM is faulty? Once again I checked the codes by bridging A and B and all I got was the 12 code meaning operational.

How can I check the system using a multimeter to find out if it's the ECM or the wiring or something else. As far as I know and from looking at the engine wiring diagrams the IAC is a stand alone circuit to the ECM, but the ECM interprets input from other sensors to adjust the IAC, right?

And also where can I find a quality re-manufactured or new ECM to put into my 89 IROC, 5.7 L98?

Any advice and help is appreciated, thanks.

 

The only way the IAC could be drawing current is if the ECM is still telling it to return to the "home" position. If the IAC won't shut off, I'd bet that the driver module in the ECM is shorted out. A lot of those "reman" ECMs are just basically recoated and thrown in a new housing, with any obvious damage fixed. Which is why I would rather get a junkyard ECM for $30 that isn't remanned as opposed to paying 3x as much for reman ECMs until I got one that would actually work for a while.

If you're really serious, look for an ECM remmaned by AC/Delco... Expensive, but who knows the computers better than those who built them in the first place and have the proper testing protocols?

 

Thanks Maverick, that's the kind of info I was looking for. As for the ECM, I found one from Howell Engine Developments for 125.00. I'm thinking about getting this one and was wondering if anyone has had any experience with this company and their products?

 

Not sure if anyone cares but I finally fixed and found what was causing the battery drain and constant draw to the IAC valve. The remanufactured ECM in my car was BAD!!! The ECM was not throwing codes at all and only showed 12. In my pursuit to find out why I had a constant draw, I started by replacing the IAC valve... not it. Then I bought a stock prom off of EBAY for my year and engine size... not it. So as my last ditch effort I called Advanced Auto this morning and ordered an AC DELCO re-manufactured ECM. It was 145.00 out the door and I had it by this afternoon. I got home, plugged everything back in, checked for constant draw with my test light, negative for draw. Needless to say, I am extremely happy that this has come to a conclusion, and wished I would have tried the ECM sooner.

 

Glad it worked out for you. FYI, the ECM I got in my car was a reman (Cardone), and quit within a month or so (after already having a full code 54 error). Opened up the POS and found one of the driver transistors broken right in half with only the metal parts remaining.

 

Glad you found your problem as I will start the same troubleshooting today. Never had a problem till last week after installing a new battery. Car sat for a week and went to take it out and battery was at .5V. Took it back to AutoZone and did a quick charge and test and battery is ok.

 

Well didn't take too long to find mine. Pulling 7A parasitic. Ended up being rear hatch motor never made closed switch. No wonder new battery died quick.