Vette C5 electrical problems
Thread Starter
Cruising
Joined: Aug 2021
Posts: 13
Likes: 0
Vette C5 electrical problems
Hi, I have long time problem with my Vette. Gives faults
P 1220, P1221 and C1278. I have been replace two time TPS sensor, battery, at first seemed to work, but at long drive it starts again. Comes “Reduced engine power”and gas pedal not working.
Things I have noticed myself:
-Often cold engine start are “Reduced engine power”(mostly I can erase it and engine works after that)
-When cold engine then engine RPM swaying up and down and sometime while drive, engine stops.(not warm engine)
-Whit warm engine comes often P1220, 1221, C1278 and sometime cant erase those errors few days.
I've taken it to the service several times, but they can't do anything, they just replace the TPS.
idont know it this normal or not, but battery goes emty when car stay about 5day.
maybe somone can help me.
P 1220, P1221 and C1278. I have been replace two time TPS sensor, battery, at first seemed to work, but at long drive it starts again. Comes “Reduced engine power”and gas pedal not working.
Things I have noticed myself:
-Often cold engine start are “Reduced engine power”(mostly I can erase it and engine works after that)
-When cold engine then engine RPM swaying up and down and sometime while drive, engine stops.(not warm engine)
-Whit warm engine comes often P1220, 1221, C1278 and sometime cant erase those errors few days.
I've taken it to the service several times, but they can't do anything, they just replace the TPS.
idont know it this normal or not, but battery goes emty when car stay about 5day.
maybe somone can help me.
Last edited by Marks1982; Mar 15, 2026 at 05:27 AM.
Race Director
Joined: May 2006
Posts: 10,455
Likes: 401
From: EAST TENNESSEE
It sounds like you’re got a parasitic draw,there’s several write ups here on the forum and YouTube about it. A low voltage condition will cause all kinds of electrical gremlins to pop up. Find the cause and the other problems will probably go away. Good luck!
Melting Slicks
Joined: Sep 2008
Posts: 3,101
Likes: 789
From: Espanola New Mexico
I know you said that you have replaced the battery, but I would pull it and have it load tested at a nearby auto parts store. I went down the parasite draw rabbit hole several years ago, but discovered that my battery was not holding a charge. Do you have a DVM and know how to use it?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,191
Likes: 3,874
From: Cape Coral, Florida
See you live in Estonia...trouble codes are NOT part numbers so find an auto electrical specialist in your area...they do not have to be Corvette specialists but have electrical experience.
