So basically I drove my car around on Saturday with almost no problems and let it sit on Sunday. This morning upon startup the car seems to be in limp mode with codes relating to "APP system" which have never come up before since I bought it 4 months ago. looking for any guidance on where to start first. Thanks.
P1125 (H/C) APP system
P1276 (H) APP sensor 1 circuit performance
P1280 (H/C) APP sensor 2 circuit
P1281 (H/C) APP sensor 2 circuit performance
P1286 (H) APP sensor 3 circuit performance
C1278 (H) TCS temporarily inhibited by PCM

A couple of recent problems and not sure if any of these contributed to the issues:
1. I still have water leaking on drivers side A pillar area. I recently had drivers door weather strip replaced and window adjusted but I still have a leak somewhere.
2. While driving through parking lot the car just shut off. while adjusting key to restart, but not turning key, it seemed to make a connection and give you all the light as if you turned key into ACC position. turned car on and drove with no problem. seems like there is jiggle issue/loose key slot that is giving connection issues.

 

So do you have electrical trouble shooting experience? APP is accelerator pedal position sensor. There are 3 separate circuits in the APP. Their output goes to the TAC (Throttle Actuator Control ) module, which is behind the RT fender. Then the Throttle position sensor tells the TAC the actual position of the throttle plate. The TAC module puts the car in limp mode if either the APP or TPS circuits toss codes. In your case, it is the APP circuits that are causing limp mode. IIRC two of the 3 APP circuits have to function AND both TPS circuits for the system to be happy.

I made a post last fall about a bad connector causing a similar problem. In your case, either your APP module or theTAC module is bad OR the associated wiring APP modules are out there, but TAC modules are a little harder to find. Rebuilt TAC modules used to be available, but to my knowledge, no one is rebuilding them anymore.

I would suggest you test the APP circuits first. You will need a wiring diagram and a good multimeter, or better yet, a Tech 2 clone. The T2 clone has measuring functions that will show you module performance as you press the pedal. I prefer pulling the connector from the TAC module and measuring voltage for each of the 3 APP sensors. That way you can test the circuits all the way to the end. where they terminate at the TAC. If you are getting good voltages, then the TAC module is likely bad.

 

I'm so-so at electrical but there will be no happiness doing this in the dark and raining. Being my daily I'll bring it into a shop. Thanks.

 

Just let us know what your shop finds...hopefully they are competent and can diagnose it to only one part and not to an APP sensor, TAC Module and TPS sensor !!

 

will do.

 

update: assessment #1

PCM was wet, mentioned that a drain hose was slow/blocked on passenger side. Also there are signs of a rat nest underneath cowl and some chewed harness wires. This will be first fix then go from there.
I was sure he said PCM, not TAC, but definitely right side.

 

There is a cowl drain udder right above the PCM/TAC Also the battery is over these modules, and battery acid leaking onto theses modules is a very common problem.

Even though the connectors are supposed to be water tight, they are almost 20 years old. If it were mine, I would take the right front fender off and disconnect both modules and do a thorough look see at the terminals in the connectors. A little cleaning, and you may have a problem solved. The APP, for example doesn’t suddenly die completely. You have all three circuits gone. Electrical problems almost ALWAYS have one root cause. Yours might be water/battery acid messing up the connections.

If you take it to a repair shop, be prepared for a good sized invoice. Unless the techs have experience with trouble shooting, they will just swap modules until the problem is fixed.

 

On passenger side the green arrow is pointing at the udder behind the PCM .
If you remove batterybase (second picture) it should be available.
The third photo show three udders on driver side

 

In the shop now as I don't have time to work on it. This Corvette has been a huge pain so far that I should've bought a beater car, too.

 

So, in this case it seems like chewed wires were the culprit. I'm sure the wet PCM didn't help but a mouse chewed 3-4 wires underneath the cowl area and this issue has been fixed and good to go.

Thanks.

 

Mice will ruin stuff for sure. Sounds like the shop got it right. They are probably keepers. For some reason, mice love insulation.
and that is an easy place for them to hide.

Some folks don’t like to poison them. My feeling: the outdoors is free space. No rent and one free last meal for mice in my garage.

 

I hear that!! I have actually considered buying a cat.....Or TWO!!!

 

Hey guys I could use some help I can't seem to get my car to idle for more the 3-4 seconds top end I completely redone codes I'm getting from the car information center
P1125
P1275,
P1280
P1285

 

These are all APP sensor DTC’s so it can be a bad sensor, wiring issue, or bad TAC module…you really need to have a scan tool to look at the APP voltages to see what you have..a DVOM can also be used to check these voltages at the APP sensor….this will take some diagnosis to nail down !!…also good idea to post this in a NEW thread and it helps us if you fill out your profile…model year, mods, tune etc…

 

1998 cam, heads, headers, intake, throttle body and I think that’s it.

 

Click on your username and go to your public profile and you can enter this info there…like I had said it can be a few things so you have to figure out how to fix this…fire the parts canon or do some detective work…there is not going to be just one easy fix !!