01 c5 ls1 6spd. Had a wire chafed on the bracket behind the left side fuel rail that shorted the harness. Blowing P1518 &1515. Hear it is common. Fixed the wire and the fuse it popped and it idles just fine. Problem comes in at about 15% throttle or 2200rpm. I get the reduced performance light, check engine light and lack of pedal again. Pull codes P1515 is the only one. Replaced the TPS got a reworked TB and only reused the throttle motor itself. No problems what so ever before. Just the P1515 now. I don't have a Tech2 to watch both TPS values. I have done the GM diagnostics except the dual TPS value. My scanner only lets me see one. Did the short take out something else? All other fuses are good. Has any one else had this problem? I am new to this forum so any help would be fab.

Andrew. sailboatluvr@gmail.com

 

I'd suggest going back and taking a good look at the wiring harness you just fixed. It'd be a crazy coincidence to have two separate issues on the same circuit at the same time.

If you're 100% positive that the harness is repaired and in working order I'd probably suspect the TAC module (next to the PCM in the passenger front quarter panel); check the wiring going to that...

 

I did check power to both sides of the damage on the wire. The rub through was just enough to break the insulation and ground the harness. The TAC is not a cheap part. I would hate to buy one just to test. Any one got a spare I could borrow? I'll pay shipping both ways.

 

I had that same problem.... did exactly what you did.. I agree with the other gentlemen. check for any other damage to the harness.. I actually took it a step further and added a piece of hard plastic ( cut a super glue bottle,shaped to fit) that little blade on the back of the fuel rail where it rubbed initially. Is the car still stuttering while driving? Or is it simply throwing codes?

 

The car isn't drivable. Just about every throttle action requires more than 15% pedal. Only found damage to one wire.

 

Okay, so you found where the wiring harness had rubbed against that sharp bracket and damaged it and your car started throwing codes. Then you repaired the wiring and still had codes and reduced power. So you replaced the TPS (Throttle Position Sensor) and the Throttle Body? Is that right?

Out of curiosity... Why did you replace the TB?

To the best of my knowledge there are only three electrical components that can cause your issue. The TPS sensor (which you've already replaced), the TAC module which is located right in front of the PCM, and the Gas Pedal sensor (the proper name escapes me) which is located in the pedal linkage. The wiring between these components is also suspect.

Since you said you got a "re-worked" throttle body I'd start by checking that out. Remove the air bridge and watch the blade with the ignition on (motor OFF). Make sure it opens smoothly when someone in the car depresses the accelerator pedal and it closes smoothly when the let off. Look for any indication it is sticking.

Since you say you've verified the integrity of the wiring you've repaired the next step is to look at the modules themselves... I've never dealt with this issue personally so maybe someone else who has will chime in...

 

I used to the best of my ability the factory diag with the exception of the Tech 2 scanner that can check both TPS values and possibly what the TAC module is doing. The GM diag flow chart stated that on the end, step 12 to replace the TB. Later models have the TPS riveted in requiring a different unit. I found what was supposed to be a complete unit on ebay from Janzer performance. It showed up bare so I bought the TPS swapped the motor, greased the gears, and tested the operation by moving the butterfly back and forth to check for binding. I did also talk to a GM drivability tech who said if the TPS had a glitch you would only see it on an oscilloscope. The almost meeting the GM statement to replace the unit. What I think to be the issue is the two TPS values don't match causing the problem code P1515. The wire rub is minor but enough to ground the harness and blow the fuse. with it moved away and a fresh fuse it idles great, throttle snap is fine. I just can't push it past 15% or the story starts over.

 

One other note; with the air bridge off and observing the throttle flap. Once the 15% region is reached the gas pedal position no longer matters the plate returns to idle and the light comes on, TPS value doesn't change (stays low) . I can remove the harness from the motor and follow the TPS value to 100% on my scan tool when moving the flap by hand.

 

Just one code now. P1515.

 

Update; I checked the voltages at both TPS's. Voltage sweeps are good (one from 4.88 to .38v and one from .40 to 4.90). I checked continuity from them to the TAC module and they are ok as well. I also checked voltage sweeps at all three APP sensors (.64 to 2.8v, 2.9 to .63v, and a third at something like 0 to 2v) at the gas pedal and their continuity to the TAC module as well. Ok. I tested the throttle motor harness continuity, tested the motor itself and all is good their too. I'm not sure how a shorted wire could have taken out my module but everything leads me to that as the problem. Well guys what do think is my problem? Anyone have a used module I can buy to test this theory?