Hello all, I have a 1992 Trans Am with a LS swap. It started as a LQ4 from a 2003 2500HD truck Drive by wire and progressed into a LS2 short block, Soler ported LS3 TB, Dorman LS2 intake, Xlink for the throttle body conversion. Being tuned by PCM of NC. I recently got the car back on the road after a couple years painting it the only thing that is different is the Soler throttle body and the LS2 short block.

The problem I am having is while driving under part throttle around 2000 rpm and 50 mph if I lift off the throttle and back on too many times it is throwing codes P1516 and P2135, I then have to reset the codes while driving.

I changed the Accelerator pedal position sensor then it drove for about 45 minutes no issues then it happed a few times in the next 15 minutes on the way home.

I checked the Xlink OHMS per the website and it read fine, also tested the throttle body per a you tube video.

I also tested the 2 TPS sensors in the Throttle body they read ( 2.30 k ohms closed and 1.15 k ohms open) the other (2.11 k ohms closed and 3.22 k ohms open) neither had any weird readings in the travel of the blade. The throttle motor read 1.5 ohms a little on the low side the video I watched said they should be between 2 and 15 ohms.

I also checked all the wiring between the pedal and TAC module and it all rang under .4 ohms. Then rang the wires between the throttle body and the TAC all rang under .4 ohms, next range the 2 serial data wires from the TAC to the ECU and they also rang under .4 ohms. The ground from the TAC module to ground was also under .4 ohms. I pulled on all the wires on each plug and non pulled out, I also wiggled the wires while testing them and no issues. The wiring harness has been in the car for about 10 years and I have never had any issues with it so I believe the wiring to be in good shape.

After confirming all the wires where good I reattached all the plugs after cleaning them with electrical cleaner and adding dielectric grease. Went for another drive and it was worse, it seamed after it started pulling the codes the first time with the new Accelerator pedal sensor it progressively got worse to the point I couldn't get around the block with out it popping the codes.

I decided that maybe the new TPS sensor was bad from stock so I purchased another, went for a test drive and it drove great for about 30 minutes or so and it happened again. Once again after the first code pop, it of course progressively got worse on the drive home to the point when I go to my neighborhood I had to clear the codes 3 or 4 times just to get back to the house. I can feel in the throttle a slight hesitation when I lift and push again, after a few lifts and pushes it happens just about like clockwork.

It would seam as long as I don't lift and push back on the throttle too many times it will work good for a while but when I am on and off too much it get progressively worse. I don't understand why changing the Accelerator pedal sensor makes it work for while then fail again, the sensor reads the same as it did when it was installed so its not like something is damaging the sensor.

Since getting the car on the road it has gotten worse, I raced 2 autocross events about 2 weeks apart and had no issues it wasn't until after that point I started noticing every so often it would hiccup like this but clear and not come back for a while.

I also swapped the Throttle Actuator Unit with no change.

Could it be bad information coming through the serial data lines from the ECU?

I am desperate as I leave for work soon for a couple months and Myrtle Beach F Body week is the day after I get home. In its current state its basically undrivable

The readings for the throttle body are
Pins C&E 1.474 K Ohms,
Pins D&E Closed 2.743k Ohms Open 3.211K Ohms Push closed 2.125K Ohms
Pins E&F Closed 2.20K Ohms Open 1.144K Ohms Push closed 2.270 the only difference in this one is that after pushing it closed if i let it back to its resting state slowly the numbers go up to 2.3k ohms then back down to the 2.20K Ohms resting state. Maybe this is what the ECU is seeing as a TPS sensor difference to pull the codes?

 

Have you talked to PCM of NC about it?

 

Not yet I didn't think it would be a tune issue since it ran fine before with the GM OE 90mm TB. Looking at the tunes, they haven't changed anything about the throttle body in the tune, just the timing and fuel maps.

I spoke to Soler engineering yesterday afternoon and they are sending a new GM never used TB, I'll have it tomorrow for me to try out. Hopefully this does the trick, especially since the test readings seamed a little off.

 

Turned out to be a bad Throttle body the new GM part worked perfectly, it may have been a knock off looking like a GM unit