1992 Corvette Running Rough Code H63
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2nd Gear
Joined: Jun 2023
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1992 Corvette Running Rough Code H63
Hello. I have a 1992 corvette that's running really rough. I replaced the distributor a month ago thinking the opti was bad. After that the car ran perfect. I didn't drive it though, I just let it idle until it got up to temp. I drove it this week and it's running really rough again. The problem comes and goes. Sometimes it will smooth out and other times not. Now as soon as I start the car it runs rough to the point of the whole care shaking. It's also running really rich. It keeps setting code H63 from module 4 which is right O2 sensor open circuit. I clear the code, drive it a bit and code H63 sets again. I measured the voltage of both O2 sensors at the ECM plug and I'm reading .385 volts on both sides with the engine running at idle. So that tells me the O2 sensors are both working correctly. I'm leaning towards the ECM being bad. I think replacing the distributor and it running good afterwards was just a coincidence. I'd have to believe if the opti was bad it wouldn't sometimes smooth out and run good. Has anybody had this issue? Any thoughts on it being the ECM? Any advice will be appreciated. Thanks.
Zen Vet Master Level VII
Joined: Mar 2016
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From: Southlake, TX
It keeps setting code H63 from module 4 which is right O2 sensor open circuit. I clear the code, drive it a bit and code H63 sets again. I measured the voltage of both O2 sensors at the ECM plug and I'm reading .385 volts on both sides with the engine running at idle. So that tells me the O2 sensors are both working correctly. I'm leaning towards the ECM being bad.
A bad ECM is in my opinion a stretch. You have more obvious, simpler fixes at the moment.
Thread Starter
2nd Gear
Joined: Jun 2023
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What I mean is I'm getting the correct voltage at the plug on the ECM. Not just at the O2 sensor plug. So I know the signal is getting to the ECM. Now yesterday I also got code H16 which is optispark low resolution. The ECM isn't seeing the low resolution signal from the optispark. It just seems that with the ECM not seeing 2 different signals that it may be the ECM failing.
