multiple issues with 03 grand prix

i have issues with a 03 grand prix. i have a snapon "red brick" scanner. i dont know if there is an issue with it only going up to 01 and using 01 settings to try and diag this but i hope not. have high idle and jerking and bucking when taking off and slowing down. maf sensor was not responding, replaced maf, now response. still high idle but occasional now. noticed tps was showing incorrect data. replaced tps still no change. noticed that the iac clicks and tps still shows wrong data. all other data seems perfect. jerking and bucking seems to be in transmission. have p0742 code. i think thats in the tcc solenoid but i dont think that has anything to do with the tps incorrect data and iac clicking. any help would be greatly appricated. thanks.

Hi, Welcome to the forum!

The PCM relies on several sensors (MAF, TPS, etc.) to properly shift through gears and properly locking and unlocking the TQ. If one of those sensors is bad it will have a hard time deciding which speed should be used or if the TCC should be activated.

I might be wrong but I don't think the year would be a problem with a generic OBD scanner, I'm not sure which snap on scanner you mean, is it the one you insert different memory boards in the OBD connector? In that case I don't know if the serial communication or memory address changed between those years, but OBD II being a standard protocol shoulnd't change at all no matter what year, brand or model you have. That's the difference between OBD and OBD II.

I would inspect the connections and wiring at each sensor to make sure they are all OK. Also check the connector at the transmission and look for bad contact or fluid contamination.

Oscar.

checked all connectors: tps, pcm, fuse block, iac, maf, map. im thinking the computer might be bad but i hate to condemn a pcm bad cause i see too many times when techs do that.

another thing i noticed is when i monitor the throttle position sensor with key on engine off it reads 10-30% if i unplug the map sensor it reads 0%. could the map sensor cause all of these issues? if i drive the car with the map sensor unplugged it does not drive any better.

Do you have a local AutoZone? they have scanners you can have them read codes with....they also read data.....check the data while it's attached...

How about unplugging MAF and TPS one at a time and taking it for a short drive. Shifting might be a little harsh just be gentle with it.

I know you already replaced MAF sensor but that doesn't rules out the fact that you might have a bad one out of the box.

Oscar.

I think I would focus on cleaning up the IAC port, checking PCV piping for leaks (as this is a controlled vacuum "leak" around the throttle blade), and possibly fuel injector seals, and the MAP sensor (note NOT the MAF).

If truly the MAP was unplugged and it ran the same I think that may be the problem right there. I think a properly functioning MAP sensor would make a big difference if unplugged and would definitely give you a SES code.