1981 ECM code 55?????????
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Safety Car
Joined: Mar 2000
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From: Northeast South Dakota
1981 ECM code 55?????????
I am finally getting my little problems from the trip to the corvette rally taken care of so I can put a few more miles on before winter. One problem was that the car was running terribly rich. I knew I had put in a new TPS and never adjusted it, so I adjusted it. It was at 3.something volts when I first hooked onto it with the key on engine off. So that would never work considering it should be .56 volts. So I pulled the plug and adjusted on it. The lowest I could get it is around .85 volts because if I would screw the adjuster screw in any farther to get it to drop a little more the TPS plunger would stick down and not spring back up, so I went with the .85. The car does run nice now, I know my primaries are working because I dropped a little piece of tubing down the hole where the plate that pushes on them is when it was running and the tubing bounced around, so we do have adequate M/C selenoid action. But I still have a check engine light, with the normal three code 12's and code 55 after that. What does your guy's books say about code 55. I have a general computer controlled engine management book and it says it could be a number of different things. What does the GM service manual for the 81' vette say?
-Justin
-Justin
Pro
Joined: Feb 2002
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From: macomb mi
Re: 1981 ECM code 55????????? (Dalannex)
GM code scanner book reads for a code 55 error is ECM computer circuit problems/ECM failure, serial bus error, SAD error or lean fuel malfunction or EGR soleniod #3 failure. Hope this helps you out!!!!! Sounds like your throttle position switch is bad if you can't adjust it to the proper voltage.Thanks, Steve :smash: Good luck
Thread Starter
Safety Car
Joined: Mar 2000
Posts: 4,078
Likes: 27
From: Northeast South Dakota
Re: 1981 ECM code 55????????? (7782vette)
What is SAD anyway??
My book says grounded voltage reference, faulty oxygen sensor or fuel lean (feedback carburetor system), ECM/PCM error, or not grounded, fuel lean monitor (Corvette and F-body VIN P-5.7L).
Now, the car was running with the primaries wide open (I think) for about 600 miles. Could the oxygen sensor have some stuff to burn off from running that rich for that long? Now that the TPS is adjusted it runs good again, and TPS signal voltage is right between that 1 volt and 5 volt range when running, it's just the check engine light that I need to get resolved. Thanks.
My book says grounded voltage reference, faulty oxygen sensor or fuel lean (feedback carburetor system), ECM/PCM error, or not grounded, fuel lean monitor (Corvette and F-body VIN P-5.7L).
Now, the car was running with the primaries wide open (I think) for about 600 miles. Could the oxygen sensor have some stuff to burn off from running that rich for that long? Now that the TPS is adjusted it runs good again, and TPS signal voltage is right between that 1 volt and 5 volt range when running, it's just the check engine light that I need to get resolved. Thanks.
Pro
Joined: Feb 2002
Posts: 502
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From: macomb mi
Re: 1981 ECM code 55????????? (Dalannex)
SAD[ System Analog Device] Did you pull the fuse in the battery box to see if the fault would clear. The sad converts eletric signal to digital pulse. Could be your ECM is ready to go but don't know that for sure.
you would have to put the system through a check that goes through each device to make sure they are giving out the right outputs to the ECM
you would have to put the system through a check that goes through each device to make sure they are giving out the right outputs to the ECM
Melting Slicks
Joined: Feb 1999
Posts: 2,473
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From: New Paltz, New York USA
Re: 1981 ECM code 55????????? (Dalannex)
Justin,
If you don't get this fixed by tomorrow let me know and I will e-mail you the whole procedure on how to check it from my 1981 repair manual. I will use e-mail because it is a long,but easy thing to do. I am going through the same thing now. I have about a million wires out all over the palce, I have a code 23 & 45. My M/c solenoid will not work. I'm not sure if its supposed to click when I turn the key on or not.
Anyway let me know and I'll get my manual tomorrow as soon as I get home from work and E-mail you the directions. We don't have a scanner so I have to use e-mail. My address rcooper1@hvc.rr.com good luck.
If you don't get this fixed by tomorrow let me know and I will e-mail you the whole procedure on how to check it from my 1981 repair manual. I will use e-mail because it is a long,but easy thing to do. I am going through the same thing now. I have about a million wires out all over the palce, I have a code 23 & 45. My M/c solenoid will not work. I'm not sure if its supposed to click when I turn the key on or not.
Anyway let me know and I'll get my manual tomorrow as soon as I get home from work and E-mail you the directions. We don't have a scanner so I have to use e-mail. My address rcooper1@hvc.rr.com good luck.
Thread Starter
Safety Car
Joined: Mar 2000
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From: Northeast South Dakota
Re: 1981 ECM code 55????????? (Richard Cooper)
I didn't try pulling the fuse in the battery box. I was going to try disconnecting the positive battery cable tommorrow, but didn't even know there was a fuse in the battery compartment. I do have a battery disconnect on the negative cable, that should clear codes too shouldn't it???
Richard, thanks. I'll let you know if I need your info. What service manual are you using anyway? Is it the GM service manual????
Richard, thanks. I'll let you know if I need your info. What service manual are you using anyway? Is it the GM service manual????
Burning Brakes
Joined: Feb 2000
Posts: 771
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From: Middleton, Id
Re: 1981 ECM code 55????????? (Dalannex)
Just looked up the code in my Haynes Corvette manual. It says code 55 is either bad ECM or oxygen sensor. If ECM ground connectors are tight than one of those two are bad. My bet is on the ox. sensor. Yes disconnecting the neg. lead for 30 seconds will clear the code. I would do that first then see if it reappears.
