Vortec5300

For some reason when I run my AC for a while, it will set the SES. I took it up to Autozone to scan it and it had a TPS code and gas pedal position code. Anyone ever have this problem. If I don't run the AC I never get a light but...for some reason, AC triggers it. I am thinking the IAC motor is not keeping up fast enough because it does have a bad surge and sometimes dies if I start it up and instantly turn the AC on. The car has been tuned and the EGR and AIR codes are turned off. The TB has been drilled and normally it idles ok after the initial two surges after starting. Car has a MAGIC STICK and is M6. Eventually I will take it back to G-Force for more tuning. I don't think they tuned anything on the idle circuit other then the idle speed so...maybe they can tweak it.


Thanks in advance for any info...

fast98

iTrader: (16)

what are the codes for? the only thing i can think of is a bad ac high pressure switch pulling down the 5v reference. check to see if those are on teh same circuit. other than that you could have a bad diode and the compressor clutch cycling on and off createing voltage spikes could mess some suff up. just look over the circuits if you have diagrams and see if any ac stuff shares a power or ground with those sensors

Vortec5300

Not sure on the codes, hell I didn't even catch the code numbers when the guy was running it. I know there is several error codes for TPS so... Its weird I can drive it around for an hour or so with the AC on and have no problem. Shut the car off for a few mins, then take off again and within 20 mins the SES is on. I disconnected the battery for now and next time I run the AC and it trips the light, I will scan it and pay more attention to the codes. The car only has 28k miles on it and the AC has hardly ever been used(weekend car). Everything seems to work OK. It never did any of this until I put the cam in and tuned it about 1k miles ago. I think its in the tuning because the car has a hard time idling when first started and its magnified 10x with the AC on. I think the idle tuning needs to be redone.
Thanks for the reply. I am not much of an electrician so...troubleshooting diodes and circuits will be difficult.

SmokingWS6

iTrader: (1)

if your getting a pedal positon code perhaps the TPS is bad or the tb screw needs to be readjusted, or reset.

Also, you may be running out of air at idle, the iac might be maxing out with the ac on causing it to die. If you've already drilled out the tb some, It might need it a bit more. However I'd have your tuner check out the IAC motor counts first before over drilling. It should read below 60 with the AC off.

Vortec5300

Thanks Josh...Its still doing it. Sometimes it may take 2 or 3 days to trigger the light. Then it can be idling in the driveway with the ac on and trip the light. I guess I need to get it back to G-Force for more tuning. They never really tuned the idle adjustments. Just the idle speed and they drilled the TB so...


Its hot as hell now, gotta have the ac useable.
You think if I drive it with the SES light on for a while it will do anything stupid? Like go into some sort or safe mode or limp mode? will it affect the tune/timing or anything with the light on?

wrencher

iTrader: (2)

Well I've ran into this problem b-4 on lots of GM cars. I've posted it here to. The TPS & the A/C high pressure switch share the same 5 voly reference supply from the PCM. The pressure switch faults while under a load (A/C running) & shorts out the 5 volt ref.
The PCM obvouisly constantly monitiors TPS input, sees low input for a short time & sets a P0122 low TPS volts.
Have seen it happen quite a bit on quite a few GM cars, hope it helps.

Johnny Ray

Is there anything we can do to eliminate this problem other than just erasing the code once it comes up?

Our '98 T/A has seemed to do it every summer?

TIA!