Thread: New GTP problems.

Hey everyone,
I just picked up a 2000 GTP, and I'm loving it so far. Easy to work on, fast (ish), all the cool gadgets, etc. Anyways, car has 227,000 miles on it, so I'm going through it doing all the typical maintenance stuff. I've changed the S\C coupler, new belts, oil change, coolant flush, seafoamed, new thermostat, new 02 sensor, new ECT, and new plugs and wires. It still has a bit of a rough idle and it runs pretty hot. It will randomly throw a P0303 misfire code (which is why I did new plugs\wires), but I don't feel it misfire, seems to run fine. The PO replaced the coil that cylinder 3 runs off of, so I'm assuming that is not the problem. Whats the next step? ICM?

Also, the e-fans are not working, If I hot wire them, they work great. I checked everything up to the PCM, relays, fuses, etc. In my research online, the PCM provides a ground to the relays to turn the fan on, so I disconnected the PCM, grounded pin 5 and 6 (one at a time) and the fans turned on exactly like they should. Fans don't come on at all (A\C on or not). I've also gone around and cleaned most of the grounds, there's a few inside the cabin that I haven't gotten to yet, as well as the main ground by the battery.

I'm not new to wrenching at all, but I am new to Pontiacs, I've always worked on Fords, so this is a new field to me. I don't mind spending the money on a new PCM, but I want to make sure it is the problem before I do. Does anyone have any feed back on input on these 2 issues?

Thanks for any and all help you guys can provide.

Edit: The PO (genius BTW...) had a wire leading from the cruise (brown wire) to the e-Fans (Grey Wire). That has since been removed...not sure why he did that.

Edit 2: I read online that if you unplug the ECT the PCM should not only throw a code, but also have the fans on all the time. I unplugged it and nothing changed, no SES and no fans. Does this mean my problem revolves around the ECT? When the A\C is turned on is the ECT bypassed (when it comes to the e-fans)? My temp gauge works fine; I know there are 2 sensors inside the ECT, one for the PCM and one for the gauge.

Check your fuse for the fans and the relay

Welcome to GPF, hope you get it sorted. Someone should be able to figure this out for you, it's over my head.

Originally Posted by Booba5185

A little bit of an update, I went into the diagnostic mode of the CJ2 (digital climate control) and checked the ECT through that. The gauge was roughly 100 degrees higher...CJ2 showed 144 degrees before I shut it down because the gauge showed around 250 degrees. I'm sure it was wrong, but I'd rather not risk my motor.

Is my ECT bad? This would be the second new one I put in, the first one made the temperature gauge peg all the way bass hot the second I turned the key.

Sounds similar to what my ECT is doing.. My guess right now is a bad ECT sensor unless someone can give me another answer.
http://www.grandprixforums.net/2-24-...ues-62870.html

did you bleed the air out of the cooling system? via the bleeder a top the t stat? if not the temp sensor may not be getting any coolant to it. or maybe a bad temp sensor.

also does the a/c work? if the compressor dont turn the fans wont come on like they should. as far as a/c is concerned.


the misfire could be a bad icm, under the coils. some times you can take the coils off and clean it up (the icm) and it will work. you can also test them.

and the rough idle, check for vac leaks, the T's like to break, under the sc snout, and the one on the fpr.

the fat vac tube that curls back off the TB to the evap also likes to hide a crack as well.

if you find your self needing a new vac line on the vac tree on top of the sc, cut the line first with a razor then remove, or your sure to break that tree. its plastic, and been through a how many heat cycles? yeah, its brittle.

the old fashioned carb cleaner sprayed around the vac lines and sensors will make the idle jump some if theres a leak. you can pin point it like that.

Infrared? This guy has a CJ2 thingee, that most of us never consider looking at.

Since you have two ECT's built together, I would have scanned the pcm temp. The PCM and gauge should be reasonable close in temp. Fans don't kick on until at least 216F or if the AC actually requests them on. If your AC system isn't up to par, the request may not be happening. Sounds like you have determined that either the ECT or your cluster gauge is bad.

Please elaborate on the cruise issue. It sounded like he jumped a ground from cruise on/enable over to the fans to make them work when he wanted, which you since removed. You didn't mention much beyond that though.

Likely you are enjoying the lack of plumbing and vacuum lines GM vs Ford. You may notice a lack of inline connectors as well. Takes a lot of the easy clean, reconnect out of the diagnosis.

It's either the tool or a parameter in the climate control that he got the engine temp from. Pretty deep stuff compared to where we typically go for the temp.

Well, there's three places that temp is possible to be found.

1. PCM (seperate feed from dash gauge)
2. Dash gauge
3. Climate control (not sure which feed this uses, probably pcm)

If you have a scanner, you can typically read pcm, if you have a super deluxe scanner you can read climate control info/codes.

the abs/trac off light. first start off with jacking each wheel up, then grab the tire at the top, push and pull it firmly, you looking for some movement. should be rather tight feeling. you can also watch the rotor where it meets the brake caliper to see if its moving.

then clean the plug to each hub, and inspect the wires that run along the lca's they get torn up sometimes.

if you cant find any of these free checks to be the problem, its best to pony up and pay to have the abs scanned, or you could be just tossing money at it.

sounds like a plan. ive heard of testing the ohms of the sensor as well, i have no idea how to do that. i truly hate electrical problems.