jwalton

Hi all, I need some help. I've been scouring all of the electrical gremlins posts and I see some similarities and some differences. Let me describe my problem.

I have a 98 Base with no modifications that could possibly relate to any of this (wheels, cat-backs, shocks and sways).

There are 2 primary issues (I sure hope they're related...). The annoying 1st one is that although I repeatedly re-sync the key fobs to the car, they don't work within 10's of minutes to an hour. The keys are still recognized and the seats move to their proper position when the key goes in the ignition, but the doors won't lock or unlock.

The really bad one is that the engine keeps going into the Reduced Power Mode, Service Traction Control System. It seems to start when I am cruising along, give it a little more gas, the car seems to hesitate and then the dash lights up. I have been noticing for the past month or so that the car randomly seems to hesitate or lose just a little bit of power (kinda like a small 4-cylinder motor when the AC compressor kick in) and then it comes back. If I'm doing a WOT type thing and the hesitation happens, the power hesitation is quite dramatic. If I'm just cruising, it's more like the 4-cyl AC thing.

The codes in the DIC are:

P1125-H
P1286-H
C1278-H
B2282-H
B2284-H
B2262-H
B2264-H
U1064-H
B2285-H
U1016-H
U1096-H

Last weekend I replaced the battery with an Optima Red Top and verified the grounds under the battery and the ground junction connectors behind the headlights. They all seemed fine with no obvious corrosion. The battery was kinda old so I just did it. I live in sunny SoCal so pretty much the only moisture happenning is when I wash the car.

Any help would be appreciated.

Thanks in advance,
Jim

msghuff

P1286 APP Sensor 3 Circuit Performance -C

P1125 Accelerator Pedal Position (APP) System

These are the two you need to worry about. I would start by ensuring the wiring that goes to the motor on the TB isnt damaged or loose also look up around the gas pedal and see if possibly a wire or connector got kicked around. reset the codes and when it happens again without shuting the car off extract the codes and see if it shows either as C or current.

jwalton

Thanks, I'll look at that tonight.

I was kinda wondering why everything was a History code considering it's a current issue. I finally put 2 and 2 together about that because everytime it happened, I would shut it off, wait a little bit, and then re-fire and continue my drive home until it happened again or I got there.

niskybrat

I have the exact same problem and my Z is still at the garage. They are pretty sure it's a lose wire or connector and are tracking it down as we speak. I had the whole pedal assembly changed out last year, but this didn't help much... so I had to wait until the codes popped again. I'll let you know when they find something out. Yes, I also cleaned the grounds...at least the ones I could get to.

jwalton

Well, I cleared the codes and drove it a little this morning. It kept giving me that throttle hesitation that I described earlier. I could almost do it on demand by just trying to accelerate. I finally got it to trip the CEL and repeat the messages I wrote about above. I, like an idiot, turned off the car because I didn't like the way that it was idling which I'm assuming immediately turned all of the current codes into history ones.

Anyway, I only got three codes this time:

P1125-H APP System
P1286-H APP Sensor 3 Circuit Performance
C1278-H TCS Temporarily Inhibitied by PCM

So I guess I need to check the grounds associated with the throttle position sensor at the throttle body and the fun pedal as well as all of the electrical connections between the two.

Couple of questions. Should I also check the connections at the TAC? Assuming that the pedal sensors are horked up, where is the best place to go to get a new one? Can the sensors be replaced without replacing the whole gas pedal assembly? I obviously haven't had a chance to get my head up in there to see if they are seperatable or an integrated unit.

Thanks in advance,
Jim

jwalton

Just a quick update. I drove it yet again and it happened just like I've explained. This time I just let it idle and pulled the codes and lo and behold, all of my H's were C's. The same three as my last post. So, for those lurking and learning, as soon as you turn the key from ON to ACC, your Current codes will become History codes. Now, to start diagnosing...

BTW, anyone have answers to the last post's questions?

msghuff

http://forums.corvetteforum.com/show...ighlight=P1286 This might be helpful post #146 esp

TTK98

Sounds like a familiar situation.Had the very exact same thing with our 98 vert.I started my diagnosis with the fine information from Bill Curlee's sticky.Thank you Bill ! He also mentioned that the tac modules on our cars should be replaced so with that in mind I began at the battery removed the tray and found some prior slight acid leakage.Cleaned all the grounds,pulled and inspected the connectors on the pcm and tac module.Checked the wire harnesses for abrasion especially at the drivers side between fuel rail and firewall (metal bracket).Checked connections at throttle body tps.Removed air bridge and checked throttle plate and bore for binding.Checked throttle pedal plug connector.The car continued to act the same so I ordered a new tac module from Bob @ Fitchner Chev. for $199.00 + shipping.Installed new tac module and same thing,guess the old one was okay.The failure would always occur at about 1200 to 1500 rpm,just about the position the accelerator pedal is maintained when driving normally.I could feel a bit of a hessitation/surge then bang the bells went off. I finaly borrowed my buddies Snapon Modis scanner (like a tech 2) and monitored the accelerator pedal position.There it was the three pots inside the pedal (non serviceable) went out of limits and threw the codes.I got lucky and found a used pedal assembly on the auction site and bingo no more reduced power and very smooth acceleration.I gave away my old tac module to another member who was having similar problems.Which reminds me I need to see how he made out.
Good luck with it and be patient you will get it!

mrC5er

I had this same problem with mine last year. I opened the access area behind the right front wheelhouse, and found a ground wire that, for some unknown reason, had been pinched/kinked, and the insulation was nicked and damaged in 3 places. I spliced in a new section of wire, reconnected to the frame ground under the battery, and it hasn't happened since.

YLWFVR

I had a similar problem about six months ago. I limped to the Chevy dealer and their diagnosis was that the fuel monitoring module/system (which is either a part of the ECM -or a separate computer -- not sure which). was malfunctioning. They replaced the faulty computerh module,,and all has been well since then. The fuel pump(s) were both relatively new, so that was not the problem.took a few bucks (well, more than a few..$800 to be exact)..but no further problems have been experienced.

It was the first major repair that I had experienced..so not so bad for a '97.

jwalton

Quick update. After a couple of days, my mechanic (I absolutley wince at the thought of tackling electrical gremlins) was able to reproduce the problem. Driving the car with a bunch of crap hooked up to it (I'm assuming it looked a lot like an ER episode in the car) he was able to see the APP Sensor acting up. A new one is on order. My fingers are crossed.

A pre-emptive thanks goes to everyone who offered there advice, guidance and general support.

0MrPickles

I had the same problem..and it turned out to be bad grounds for me. Re-terminating the eye-ends and scrubbing down the metal where the connection is..worked for me.

Good luck!

knightbird

The same happened to me today, exactly as explained above, and threw the same three codes, amogst others. I cleaned out as many ground connectors as I could and started the car. Still no luck. Check under the battery, everything looks fine. All wires properly attached to pedal assembly and throttle body. Interested to see if the APP sensor solves this problem...

knightbird

Anything progress with the APP sensor? I tried recleaning all the ground connectors and taking the battery out again, still the same problem. I have done searches on other posts with the same error message, but none are spitting out the same three codes as in jwalton's post. Please help

niskybrat

Okay, I've been reluctant to post any updates until I was sure the problem was fixed...and so far so good. It was a lose wire inside a bundle of 12 white wires going into one of the computer boxes RF wheel area. Now I was waiting for my new Corvette Service Manuals to arrive so I could be more technically accurate. But since I saw the "Please Help" sign-off, I thought I would let you know what I was told. By the way, the Z06 was at Rosenthal's Chevrolet/Jeep dealer in Arlington, Va., for three weeks. They worked on it.... off and on and finally traced it down...and guess what? The bill was only for 1-hour of service work!! Now that's what I call a good service center. When I have more time we can discuss the other two service centers that didn't fix this problem and the large bills that they gave me for replacing perfectly good parts.

knightbird

Thanks for the help. I've taken the battery out again looking specifically in the area you mentioned and am patiently trying one wire at a time. When your manuals arrive, please let me know which affected you, as I will pay closer attention to that group of wires. I'm still scratching my head on this one, but I appreciate the help

Z OHHH 6

Any Updates? Going through the same situation with my C5 Z. same codes as well!!

niskybrat

Well I finally received my three (3) books manual for the 2001 corvette but still haven't figured out where those bundle of "12 white wires" are. I'll take my manuals to the dealer and have the mechanic point it out to me...... but in the meantime, I did read that this appears to be a common complaint from the customer (us) and the advice given is to check harnesses for lose wires/connections that may have been installed too short and after awhile, the connections/wires can become dislodged through vibrations/bumps/etc...which is what caused my "Reduce Engine Power" DIC to engage.

Z OHHH 6

Quick update on my C5 Z. Let me start out by saying i did a hood and air bridge replacement. I replaced my air bridge with a carbon fiber one and put on a breathless performance hood. Anyway long story short, after a few weekends of taking the car out(not a daily driver), on the third weekend since the replacements i was driving along and got a reduced engine power and service traction control on my screen. pulled over and restarted the car ran fine. did it again about 15 miles down the road, same thing restarted and everything was fine. Made it home and was doing some research i checked my codes and they showed to be my APP (accelerator position sensor) and TB throttle body. So after checking all my connections to the APP and Throttle body etc. i found no problems. I happened to glance at the new carbon fiber air bridge that i installed and BAMM there it was!!! my hood had shut on top of the air bridge and caused it to split down the seam on one side. I replaced the airbride with the OEM and have drove the car about 200 miles since and no problems .
So basically i just wanted to post this incase it could be useful to someone else. The codes are great but sometimes that lead in the wrong direction and cause you to spend money that you don't need to!!

knightbird

I have been under the battery for a few days now and I even checked the air bridge and everthing looks nice and tight. I did however stumble upon something as i looked behind the front fender, almost where the passenger door meets the fender, and noticed what looks to be a severed small vacumn line of some type. I looked a bit deeper, but it is almost out of arms reach, and I do not know what it is. One of the other vacumn lines hooks up to one of the bundles of wires below the battery, but I do not know where this severed vacumn line leads to, of what system it is a part of. I don't know if anyone has access to diagrams that could help, but it defintely seems like it should hook up to something. When you remove the battery and look below and behind the computer at the inside of the fender wall, that is where the line comes from. We are getting close guys... If anyone know what this system is or what is does or where it goes, please let me know