Here's my situation.

I have a 98 coupe with 25k.

It's starting to act up. I get the following errors -

The check engine light comes on, and I get a display of "Traction Control System Alarm", "Service Engine", and "Reduce Engine Power".

It also idles like crap, and I can't rev over 1200ish rpm.

I had the check engine light scanned at Autozone, and it said - TPS 1 & 2 bad.

I called the dealer and it seems you can only replace the entire throttle body, not just the TPS sensor.

Anybody have any problems like this ever?

 

If you pull up the codes on the DIC and post them here, myself and others, I'm sure, will check the 98 service manual and attempt to convey diagnostics.

 

I believe this is the error -

P1221 TP Sensors 1, 2 Performance

Is it possible to just put in a new TPS sensor, vs the whole throttle body assembly? It looks like it comes off with a torx security bit.

 

OK, here is what the Service Manual states about the P1221 code:
The throttle Position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. 2 seperate signal, ground and 5.0 V reference ckts are used to connect the TP sensor assy and the Throttle Acuator Control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage increases as the throttle opens, from below 1.1 V at 0% throttle to above 3.7 V at 100% throttle. The TP sensor 2 signal voltage decreases from 3.7 V at 0% throttle to below 1.2 V at 100% throttle. Observe also that the signal ckt for TP 1 is pulled up to 5.0 V and the the signal ckt for TP 2 is pulled to ground within the TAC module.

Conditions:
TP sensor #2 disagrees with TP #1 by > 7.5%

Action Taken upon DTC setting:
If no other TAC system DTCs are set, the TAC System operateds in Reduced Engine Power mode. If certain TAC system DTCs are sert at the same time, the TAC system either defaults to a more tightly restricted mode of operation if the TAC determines that limited safe operation is possible, or the TAC commands the engine to shutdown.

Diagnostic Aids:
IMPORTANT: Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly.

The following may cause an intermittent:
Poor connections. Check for adequate terminal tension
Corrosion
Mis-routed harness
Rubbed through wire insulation
Broken wire inside insulation
Inspect the TAC module connectors for signs of water bintrusion

------------- With all that said, do you need to perform the diagnostic? The procedure indicates replacing the thrittle body and if that does not correct the situation, replacement of the TAC module is indicated. The service manual does not indicate replacing the sensors only. It does rfer you to the body and accessories wiring daigrams to correct various ckts.

HTH

 

If you do have a bad TPS I have one for sale, brand new cheap!

I had the same exact set of problems you did last year. I bought a new TAC module and a new TPS module for a weekend diagnosis session.

Turned out to be a bad wire going to the TB itself. I told the TAC but still have the TPS.

How often does it happen?

Best bet is to find a buddy with a C5 and swap the TPS sensors. Only takes a few minutes and if its a constant problem you'll get your answer quickly.

Other thing is to check the grounds which I believe is in the Electrical sticky at the top of the forum.

You can replace the TPS by itself however you will need a safety torx drive. That is the Torx drivers with the pin in the middle.

 

I Had The Same Problem With My 98 And Turned Out To Be Two Problems.the First Was Believe It Or Not A Loose Battery Terminal And The Second Was An Atc Scanner Was Used To Pull The Codes And That Threw The Tps Code.the Funny Thing Is It Was At A Gm Dealer For Two Days And They Couldn,t Find The Problem.a Former Gm Mechanic Figured It Out For Me.got The Car For 16k Because Of This.hope It May Help You.