I have a 1997 4x4 5 speed that is a California truck. I bought it two years ago.

Last weekend I removed the EGR air horn and replaced it with a stock 49 state air horn. I drove it around the block to be sure everything was running right and I noticed that my check engine light did not come on. BTW I have a circuit that Dan Avila sent me that will "fool" the ECU to see a rise in temperature on the intake manifold temp sensor so the CEL will not come on.

Anyway, I took the dash apart to find the check engine light bulb missing. This explains no light from the missing EGR valve but I was concerned about why it was removed.

I borrowed an OBDII scanner and connected it up to the truck. I got three EGR valve related codes that I expected and one I didn't. This is what the scanner said:

P0123 - throttle/pedal position sensor A circuit high output

I thought only trucks with automatic transmissions had a throttle position sensor. This is very strange to me. The only 2 conclusions I can come up with are:

1. THe scanner has the wrong message for code P0123 (unlikely)
2. The DPO had a bad ECU and bought one out of a truck with an automatic transmission and rather than fix the problem he pulled the CEL bulb.

Are ECUs from manual and auto transmission trucks interchangeable? I know that GM vehicles during the late 90s had interchangeable ECUs. There was a removable PROM that went with the vehicle that had to be removed from eth old ECU and put into the new one. Did Chrysler do something similar with the trucks?

If anyone has information that could help me I would appreciate it. This explains why I haven't seen the CEL light come on when I turn the key to on to warm the grid heaters.

Bob

 

I think point #2 looks like the culprit. Either way its not a shut down issue.

 

The auto and manual PCMs (no ECU on a 12 valve) aren't interchangeable.
In fact the only PCMs that interchange are '94 and '95 auto to auto and manual to manual.
I don't know if the dealer can maybe reflash the PCM to the correct vehicle.
My bet is they don't know either. After all the 12s are getting pretty old now.

 

If my PCM is from a 97 5 speed why am I getting a TPS code?

 

I just got off the phone with the service department at Capitol Expressway Dodge in San Jose. He said that there is a TPS on the 5 speed diesel truck in the engine compartment. He said it is a small sensor that is hooked up to the linkage somewhere. He knew right away because he changed one on a 2nd gen CTD this morning (what are the chances). I asked him if a 96 had one and he said yes (I have my friend's 96 factory service manual so I was interested).

This is all news to me. Why would they put a TPS on a manual truck? I can't figure out what purpose it would serve.

Anyone have an idea?

 

I have the empty harness plug where the TPS should be. There is no TPS on this truck..

 

Me too. I can't wait to get home and check my throttle linkage for a TPS. I ghaven't seen one ever or heard of one, but the dealer says there is one there.

 

No TPS on my 97 5 speed, there is one on my 97 Auto truck though.

Bet someone stuck an Auto PCM in your truck at some point in the past.

 

I just called the auto parts store I deal with and got the part #s for the PCM for CA manual and auto as well as 49 state manual and auto trucks.

If you have a minute would you mind looking at your trucks and posting the part number on your PCM? These are the PCM numbers I was given:

CA manual 56040452
CA auto 56040454

49 manual 56040451
49 auto 56040453

 

The guy at Capitol Expressway was working on a 24 valve, both manuals and autos have a TPS.

Remember if you buy a new PCM that it may have to be flashed by the dealer to work correctly. Most charge $75 but you may want to find out if they even know how to do it.

 

The CA model 12 valves have a TPS. It is how they regulate the EGR.
A 48 state PCM should clear the problems. If they are passive codes (which I expect on a 12 valve) they shouldn't affect anything except the MIL (check engine) light.
Maybe there is a way to by-pass the old EGR control with a jumper.

 

I have a EGR bypass circuit that a guy named Dan Avilla sent me.

I looked at my truck when I got home and saw the TPS. When I sat down and thought about the EGR circuit it all made sense. The PCM must use the TPS and crank angle sensor to determine load and trigger the EGR.

I still have a code for the TPS. This may be why my truck ran rough before I got rid of the EGR air horn.

Does anyone know if the TPS crosses over to another vehicle? I am willing to get one at a junkyard. They want over $200 for a neqw one at the auto parts store.

Bob

 

I would put a rheostat in place and forget about it...

 

Any information on how to do this?

 

I was just searching on this.. Haven't got the exact answer yet..