Hi guys. A few months ago, I posted about my 2000 SLE misfiring. After replacing the catalytic converter, plugs, wires, and ignition coils, I finally narrowed it down to the ICM, which solved my problems. Or so I thought. It worked fine for a few months until the light came back on. It wasn't misfiring. I borrowed a scan tool and it threw a code for a bad upstream and downstream O2 sensor. I replaced those, and the car started running better. About a week later, the misfires start back up. I stalled a few times trying to drive my car 3 miles to my house from work. The light was on, but I didn't bother scanning it because I could tell it was missing. We found that the coils weren't getting spark and figured that the ICM was faulty so I replaced it under warranty, but it was still misfiring. At this point, I became fed up with throwing money at it, so I had the Chevy dealership scan it today. According to the dealership, it's throwing an O2 sensor code, but the O2 sensors themselves are working properly. They said they tested the ECM and it's allowing too much air into the engine. I was quoted $800 for the parts and labor for ECM replacement. Considering the fact that I found the ECM online for $150, it doesn't seem like something I need to go to the dealer to do. I know that the ECM is under the air intake in the engine compartment. Does it need to be programmed by a Tech III, or is the chip removable?

Did you check the mass airflow sensor?

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-Ryan
2004 GTO....LS1, LSA supercharged 525whp, 6MT
96 SSEi...September 2010 COTM........GONE
04 GTP comp G.... December 2015 COTM........GONE
2013 Audi Allroad Quattro

I'd sell you an ECM for $50. You can program them yourself without any special tools, just 30 minutes of waiting.

I'm gonna guess its not the ECM though. If you are using aftermarket ICM's, that is probably the problem. Try a ACDelco ICM.

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Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Why would the dealership's diagnostic tests say that the ECM is bad then if it's actually the ICM?

Dealerships aren't the know-all/end-all. They they were, they could guarantee that its the ECM. They will not guarantee it. If they replace it and it doesn't fix the problem, you are still out the costs of the part and the labor.

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

What makes aftermarket ICMs so bad? Also, if the Delphi and ACDelco are the same ICM like most ACDelco and Delphi products, then I don't think the ICM is the issue. It was running a Delphi ICM until it started misfiring again. I picked up a brand that I can't recall the name of from O'Reillys (it has a white body vs Delphi and ACDelco's black ICMs). The swap in ICMs made no difference in how it ran.

China

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Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Are the Delphi and ACDelco ICMs the same?

They should be of the same quality.

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

aftermarket parts are fine... the problem is they are run in a very hot environment..and the ICM sits on a heatsink basically... cheap chinese aftermarket parts FAIL at a high right if they work at all... i had a aftermarket ICM BLOW UP basically after a few months....