So, I've been fighting the P0121, throttle position sensor range error problem. I had the cable connector to the switch modified per the service bullitin and it helped for a while, but now I've got the problem again. My question is, why does a new throttle body help? Why is it I have to replace the entire throttle body. The sensor dosn't appear to be particularly special, there are places everywhere that give adjustment instructions for various TPS switches?

Does anyone know what actually goes wrong and what the new throttle body / switch does that the old one dosn't?

 

It appears no one heere seems to know from the responses so far.

I will say something interesting, I was frusterated because I finally got my missfire problem to go away (P0306, see previous posts), only to get the P0121 TPS out of range and engine failsafe problem back.

About three days after the P0121 showed back up, I started getting a coil fauld on cylinder 1. I moved the coil to 2 and the problem followed. I replaced the the coil, and plugs while I was there anyway. The TPS error went away.

I started looking at the wiring diagrams, according to the drawings I have, the ignition coils circuit and the TPS both have wires on the same connector on the ECM. My experience with industiral automation and controls tells me this is probably related. My hypothisis is that the failing coil was effecting the TPS via the ECM. So in this case the TPS must be more sensitive to interferrence, voltage fluctuations, ground problems, etc or the ECM may have an issue.

Anyone else had a similar experience? Other ideas? Cross my fingers, car's running great right now.