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My 99 hardtop 6spd has been throwing 1125 and 1276 with reduced engine power and service traction control system on every start now. Car was at Chevy dealer for 3 weeks where they replaced the pedal, TAC module and rewired the throttle body. They went thru all the usual procedures in the book. They even called the techs at GM and none of them had any idea what to do next. I can clear the codes and then car will run great until I turn it off and try to restart it after it's been off a while. Dealer said it needs a new wireing harness which is not availible for the hardtop anymore and could be the traction control system which is also not availible anymore. I can't even sell or trade it in this condition, I can only sell it to a scrap yard for parts! Sometimes after the reduced power is cleared and with no codes showing I still won't get any pedal response until the pedal is pressed passed 2 inches but will get full rpm range. If I then drive a minute or so and turn the car off then back on it will be fine, until it's turned off again for a few minutes. Any other ideas?

 

Wiring harness from a junkyard or a new engine mgmnt system like Big Stuff 3, depends on how much you already have invested and how much more you're willing to invest. If the car is in otherwise pristine shape, I'd first try a replacement harness from another car. With today's "parts finder" junkyard networks, it should be the most reasonably priced. A Big Stuff 3 will run you about $2,500... All I can think of off the top of my head at the moment. Good luck!

Just remembered; see if Painless or another vintage parts company makes a replacement harness... Also, all the computer parts can be had used, as well.

Best regards,
...z

 

Does the Big Stuff 3 system bypass the accelerator pedal sensors and reduced engine power problem? Is it a big deal to install? The car has 97k miles and runs great otherwise.

 

There is no sense in spending that kind of money, for what may amount to a $10 repair. A few things need to be evaluated during the failure:

1) 12 volts to pin 7; C2 of the TAC
2) Resistance to ground on pin 15:C2 of the TAC
3) Inspect S120

 

Normally, it's something you'd use on a race car, and maybe use a Painless race setup for lights, etc., if they were required for whatever race class you'd be going for. It would be for example, taking a junkyard engine & trans to put in a rock crawler, drag car, etc. So, yeah it's a big change, you'd be basically eliminating the GM engine & trans controllers, computer, everything to do with the drive train. I don't know what all you could disconnect and still keep other functions working, but I'm sure it's been done, I'd check for some racing forums for folks that have taken a C5 and turned it into a drag car. I know there's at least a couple of guys on this forum that have done that, you might PM Vega$Vette, I think he has one he has removed stuff from to race, and he would know a lot more about this than I do. That system would be a last resort for you though, for sure. But, if you can't find another way to get the right wiring harness, it WOULD work for a smooth running, powerful engine. You'd probably lose Active Handling, ABS, anything like that, not sure what all was on a '99.

Is your only choice using this dealer for mechanical work? At this point, I'd want another opinion from a good garage; give them the history, and see what they come up with. Someone like that would have resources for tracking down NOS and/or good quality junkyard parts, too. Dealers can't work that way. If the car is otherwise decent, don't give up, check around your area for good mechanics/garages.

I feel for ya man, but I'm sure you can solve this without spending a small fortune, and it still be worth keeping the car and/or getting it to where you can at least feel okay about selling it or trading for a newer Vette.

Best regards,
...z

 

I found a Corvette only shop south of here called Eiseman's Corvette's who does A to Z on Vettes. I'll try him as the dealer turned out to be a BIG dissapointment. I've owned 4-c3's, one c4 and have really loved this c5. Can't afford a c6 so Hope this guy can find the bug in the wires. I'll print out the checks on the TAC connector suggested above and take them to him also. Thanks.

 

Eisemans in Jupiter is good. Which dealer did you go to? Suburban Chevrolet in Stuart has been a good dealer for me but I am guessing that is where you went?

 

THERE y'go!!! Like lucky131969 says, it might be a $10 parts fix. Let us know what they find, that dealer has put you through the wringer...

Best regards,
...z

 

Does the car seem to run OK before the codes and messages come back ?? I would guess YES---I would check to see if the TPS is working with a scanner( after codes are cleared)
Start and watch the TPS % to see if it changes as it should
Rather then sorting out the actual cause of the situation and spending so much time and $$ on it--If it were my car I would just have your local tuner--turn OFF all the enablers for those codes P1125 P1276--The car shouldn't go into reduced power again for those codes . Also you can Disable or desensitize your traction control system if somehow the TC is involved with triggering those codes - I do it all the time-- especially on older C5's when people don't want to spend $1000's on finding out what causes it--It could be a glitch or some wearing in your T-Body---but again---if the car seems UN-AFFECTED with codes off and runs normally until reduced power comes on---Most likely it is a FALSE CODE anyway--
If disabling the TC is the ultimate fix---Just use common sense while driving and be careful as you won't have any TQ reduction--Don't let the kids drive it---LOL

 

It's weird but after getting the reduced power-service traction control bs, then going thru the routine of clearing the codes the pedal will work with the full rpm range( but only after pushing it past 2 inches or so.) Then if I turn it off then back on it works REALLY great. I mean the pedal is so sensitive it feels like I have extra horsepower if I even lightly touch it until I drive it for a mile or so then it is back to normal again. I don't know if the traction system is triggering the reduced power or the pedal sensor 1 is triggering the service traction system. It's ALWAYS sensor 1-performance on the pedal sensor. I didn't know you could disable the reduced power function, but turning off the traction control via the button on the console before starting doesn't seem to prevent the reduced power problem. It's got a new TAC module and the dealer rewired and checked the throttle body, plus they put a new pedal in(the last one in the US I was told) and that didn't help. I guess a few vette guys will have to die pulling into traffic then having the reduced engine thing happen like almost happened to me last week, before GM does anything. Athough I was told by the mechanic that the old GM is gone and the new one doesn't give a crap about cars made by the old one. It's a shame that c5's are old GM so good luck with service and parts for them!

 

If you want to fix your problem start here, if you want to keep throwing money at it take it to the dealer again

 

If you can do your own work start with this. Lucky is one of the forum's best...

If you can't; find a local corvette club and ask them to recommend a shop. NEVER EVER take it to the dealer unless you like paying super inflated prices for average quality work (usually the case).

 

Are you POSITIVE that the STEALERSHIP installed new parts???????? If it were me,,, I would lay eyes on the tac and accelerator pedal sensor and see if there new!

Theres a main engine wiring harness that runs down the drivers side of the of the engine. It where the head meets the intake manifold. It contains the injector wires, MAF wires, Throttle sensor wires etc..

That harness goes to the back of the engine and DOWN to the large main harness above the belhousing. Where the harness bends around the black metal bracket at the back of the fuel rail, it can chafe and rub theu the wires. Ive see this on a dozen or so cars with some pretty strange results:

Here's a pic:





See if the wires are rubbed thru and contacting the metal bracket.

Bill

 

They are a reputable dealer but you never know. I took it to a Corvette specialist(Eisemann's) nearby today and he was checking it out as I write this. Of course since I had to clear the codes to drive the car down there he wasn't pulling them up so I hope he'll get them in the morning like I usually do. I gave him the suggestion on what to check from Lucky so hope that helps him too. Keeping my fingers crossed!

 

I agree,suggesting that you need a new harness sounds like a guess from a tech who is not up to par. Sadly many don't understand electrical work.Find a good tech and it will probably be a relatively simple fix.

 

rolexfix, please keep us posted on your progress. Good luck.