Catman58

Bought a 2001 C5 Coupe 52,000 miles on it. The car runs fine on short trips less than 50 miles. Here is where the problem starts. After traveling 100 miles stopped to get something to drink. Came back out and when ignition switch was turned on DIC had reduced engine power, and service active handling. Retrieved codes and they were P1220, P1221, and C1278. Cleared the codes started engine drove another 75 miles with no problems stopped for lunch. Came out switch on same thing. This happened every time the engine was shut off. When coming out of the hills stepped on throttle and same codes thrown basically coasted to turn out throttle had no response and engine was idling at only 400 RPM reset codes. As long as I eased the throttle up and stayed under 2000 rpm on acceleration and at driving speed I nursed the car back home. These are the only codes coming up. Next morning cleared codes and car drives fine. I have changed the TPS and installed new battery with no results. Seems to be heat related. This happens every time car is driven over 100 miles??PLEASE HELP.

Chicago1

http://forums.corvetteforum.com/c5-t...code-help.html..
http://www.z06vette.com/forums/f5/pr...ndling-116141/ post 4...

looks like your tps may have took a dump.

Catman58

Just replaced the TPS About a week ago had the same issue before replacing it thought for sure that was the problem then. I am thinking wiring but have no idea where to start. Seems weird to me that this happens after traveling over 100 miles could it eh heat related something sticking? Have also checked the under hood ground on left side fender well it was clean no corrosion.
So this morning I clear the codes. Cannot clear the P1221 code. While in manual diagnostics switch on engine off press throttle to floor and back get a P1516 code along with the P1221.

Chicago1

have you checked the harness on the tps side? you may have to unwrap the factory tape,

Catman58

Will take a look. I cleaned the throttle body was not real dirty and seemed to move smoothly.
Am Los getting a P1516 code now. What is scary now is when you start the engine it goes to 1000 rpm and slowly keeps increasing. There is zero control with the foot feet. Looks like now I can't even drive it to a shop if I have to. By the way I really appreciate your help.

Chicago1

take those codes that you have and do a search or just google them and you will see lots of threads about it. I just picked the first one I seen and they had the same issues. No problem I'm sure some of the experts will chime in but it's a holiday so it's slow around here today

Catman58

Thanks again

tommypenguin

In for results on what ends up being the cause.

Catman58

Problem turned out to be water in the TAC module plugs. Why on Gods green earth did GM put those modules in the right wheel well? The plugs also had a rinky dink plastic cover over them from what I could see all they do is fill up with water when it gets wet. Cleaned and dried the connections and siliconed the backs of the plugs where the wires enter the plugs to keep the water out. Also siliconed the cover edges in the wheel well and under the car. Wanted to get some time and miles on the repair before I posted the fix. Has been running great since this repair. Thanks for the help.

martysauto

Well done! How did you find the problem?

bjones7131

I am like marty, how did you figure it out. What are the tac module plugs?

martysauto

He's referring to the harness connectors at the tac module. I was wondering how he got there.

Catman58

That is correct the harness ends that plug in to the TAC module. First verified all the grounds as described in a sticky by Bill Curlee (thanks Bill) then just started checking harnesses for rubbing the started on connectors on all the components that were involved in the fault codes that I had. Pulled right front tire and removed cover to inspect and check the TAC module and ECM connectors. Removed the rinky dink plastic covers on the TAC connectors and there was water in the covers, disconnected harnesses and water was dripping out of both of the connectors. At the TAC module both connectors on the ECM were dry. Blew the connectors and the receptacle on the TAC module out with air. Plugged everything back in and checked to see if I could clear the codes. All codes cleared and have not returned in about 1000 miles. As I said I siliconed the back of the harness connectors so water could not enter and siliconed the inspection covers in the wheel well and under the car to prevent water intrusion. By the way the little plastic covers made their way to the trash can. Still think there is a better place for the 2 modules besides behind the fender well.