Superduperduty

Please help. My 2000 C5 displays p1125 & p1281 codes after going to reduced engine power. Replaced pedal assy. & tps on engine with no
results. Took it to Chevy dealer, they "repaired high resistance wiring in circuit 1274 and replaced female tac module connector for that circuit."
It still does the same thing. Now they say it needs a $800.00 tac
module. I know how to get to the tac module but I cant find one for sale. What do you think? Could it be the tac module to throttle pedal
harness and is that something a do it yerselfer can do ?

funky_thumper

See the "2001 TAC Module Repair" thread.

You can get a TAC module cheaper at PSI if they still have any.

If that's the only codes you get and they are the same ones over and over, it's possible it's a harness. Could be just a couple wires have been damaged, rubbing somewhere.

You can get them from the gmpartshouse I think. It was $60 or $80 for the harness. When I look at how the cable harness is routed, it looks messy and I really never did get a good idea where it went through the fire wall. It looks to be a pain to route.

Since you already had the AP replaced (hope you got the old pedal back since there's nothing wrong with it) that kinda leaves the harness and TAC module.

I'd find the threads by Bill Curlee about cleaning grounds since that's cheap and nothing lost if there isn't an improvement.

My errors got progressively worse (happened more often). Hot weather and someone in the passenger seat aggravated it even more. The bigger the person the more likely the error would happen. It got to the point where a 6'5" 250lb person in the passenger seat stomping on the floor and bouncing in the seat with the car idling would cause it to error.

It's your choice on the harness or TAC module. One's more expensive (if you can find it) but easy to replace. The other is cheaper but harder to install.

Superduperduty

Thanks for the info. I have new tac module harness pigtails with plugs coming from EFI Connection. Since the Chevy Dealer found "spread" wire terminals in one of the tac module plugs I figured I'd try that untill I can find a TAC module. I will let you know what happens in about a week.

Bill Curlee

There are NOT any grounds that effect this issue. Look at the engine wiring harness on the drivers side of the engine. Loom where it goes towards the rear of the engine around the BLACK bracket at the rear of the fuel rail:



If the wires are chaffed / damaged there it will cause your issues/

BC

Superduperduty

Thanks Bill, I checked that location for damage at the black bracket. My harness has a slight amount of clearance,it doesnt rub there at all. I purchased a TAC Module from PSI yesterday, it will be here in about a week. I hope that will solve the problem. My Corvette only has 24,000 miles on it, always garaged and no sign of corrosion or rust anywhere. I will let you know what happens. P.S. I contacted GM customer service last week, they were no help whatsoever.

ALLEGRO

Over my head.

Superduperduty

After replacing the tac module my Corvette would still occasionally go to reduced engine power. I removed the battery and battery tray and upon very close inspection I found that a rodent of some kind had chewed the insulation from several wires of the tac module harness near the firewall. I then soldered in new wires and individually placed heat shrink tubing on each wire followed by 3M liquid tape.(thanks to the help of my Wife who has much smaller and more nimble hands than mine as the wire damage was in a very difficult location to reach) No more problems but now I have a good T.A.C. module for sale.

Tuscany103

Thanks Bill, My inspection indicates I have the condition shown in the photo you posted. Can the wiring harness be removed and repaired? and what is the procedure?

Bill Curlee

Just un-wrap the harness and find the damaged wires. If the wire strands are not damaged, seperate the wires and coat the wires with liquid electrical tape. Use a couple of coats. If the wire strands are broken/corroded, just splice in some same gage wire.. MAKE SURE that you solder the splices and DO NOT use wire crimps.

You can also apply a little electrical tape to the damaged wires.

Repape that harness. Put a piece of split rubber vacuum line on that bracket and adjust the harness to prevent it from contacting the bracket.

Thats how I would fix it.

BC

Tuscany103

Bill, Is shown in your photo there is very little space to work on this wire bundle. Can you suggest a way to loosen or remove the bundle? Thanks

Supercharged111

Remove the intake manifold. I bet you didn't want to hear that. Unless it unplugs somewhere without too much asspain and can be removed from the car. I believe that option would yield cleaner solder joints.

Bill Curlee

It does NOT unplug easily. Remove the manifold and there is plenty of room.

Tuscany103

Thanks for the advice. I want to think this over before I tackle removing the intake manifold.

Bill Curlee

Intake manifold removal is a SNAP!

Tuscany103

Thanks Bill, I don't have a service manual but it appears that as a minimum I would have to remove the injector manifold and the injectors to get at the bolts securing the intake manifold. Is there anything else. I have never worked on this car. It's my wife's Corvette she has never had it in the shop.

vectorz

I'm a mechanical novice and was able to do it by taking my time but if you follow my very old DIY oil pressure thread, it has pictures on how to remove the intake

http://forums.corvetteforum.com/c5-t...y-vectorz.html

Tuscany103

Thank you, I can do that. Very nice of you to help.

bikerjim2000

Good spot for everyone to check and do a little PM on that wire harness. My 01 was right around the upper rt corner of that bracket and tight. got to it before it chaffed, a bit of tubing goes a long way.Excellent Pics Mr Bill

Bill Curlee

The Injectors pop out of the manifold with the rails as a single assembly. You DO NOT need to disconnect the fuel line. Just flop the entire fuel rail/injector assy back on to the cardboard covered windshield. Then disconnect all the stuff on the manifold. There is a SHORT vacuum line that attachés to the back of the manifold. Go to AutoZone and purchase a nylon vacuum line repair kit and lengthen that vacuum line for an easier trouble free re-installation.

Bill

nitemaher

Bill ,
Thank you for helping everyone on the forum without your knowledge many of us would've spent lots of $$ on repairs they can do themselves . I always do a search for things I need to take care of and you are always there to help out so Thank you and if you ever come to the mid-west (we dont have any subs here though) please let me know and you can be my guest at my resturant. I am the Senior Kitchen Manager for The CheeseCake Factory in Overland Park KS. and it would be an honor to serve you