I have a 1999 Saturn SL2. The check engine light came on and the car started shifting harder than normal. I had the codes pulled and the following came back.

P0717 ISS
P0452 fuel tank pressure sensor
P0113 Air intake temp circuit

I have replace the air intake temp sensor, the ISS and put a new fuel cap on the car and still the symptoms stay the same as before.

The car sometimes will shift race car hard, at other times the check engine light goes off and the car drives normally. Sometimes the car drives normally even when the check engine light comes on. Prior to this the check engine light was not on.

I checked the voltage at the air intake sensor and I got around 5 volts on the hot side of the plug which from what I read is normal. On the ISS I checked both sides and I wasn't detecting any voltage when the car was at idle, when I did it was around .5 volts maybe. However I could find anything that said for sure what voltage if any I was supposed to get there.

Since all three codes tripped at once it seems as if a common ground is missing (unlikely) or something else that ties all three items together in sort of an works/doesn't work scenario.

Anyone have any idea as to what might be going on or something else I can check? Thanks for the input, it is starting to drive me nuts. :-)

 

Noone has any ideas? This is quite annoying.