Thread: Stalling - no DTC codes

2000 Grand Prix GT 3.8L 4T65E

Brief history: Bought the car with 121000 miles. Right front fender damage but sub-frame and other structural parts are straight. The transmission would shift hard so I figured the EPC was set to max. The engine would run rough with a bad miss. Initially DTC's 0716, 0303, 0203. After troubleshooting discovered that transmission 20 pin connector wired incorrectly and after rewire the hard shifts are gone. Also found bad wiring in harness, rubbing against AC accumulator. Input speed sensor wire(red/black) and others repaired. Checked #3 injector wire to control circuit, OK. There are now no codes after about 300 miles of driving and the car runs perfectly.

New problem: Sometimes the car just stalls; no fuel pressure. Replaced the fuel pump(knee jerk reaction). Still stalls. After toubleshooting there is no signal to the fuel pump i.e. no prime signal and no run signal. Let it sit for a few hours and it starts right up. Also if I, immediately after stall, jump the positive wire to the fuel pump it starts right up. Remove the jumper and it stalls. There are still NO DTC CODES! For some reason the fuel pump signal just disappears and then after a while it comes back.

Question: Does anyone have the PCM pinout for this car? I'm trying to figure out if the PCM is telling the fuel pump to prime when the ignition key is in the 'ON' position immediately after a stall. If the signal is being output from the PCM then why is it not at the pump? Any ideas?

Any help regarding this issue will be greatly appreciated.

Thanks for the replies.

Sabrewings
Already replaced the relay - first thing I did. I would like the pinout for future reference.

beast3300
I'll drive the car for a while and when it stalls I'll do what you said.

Update
Replaced Igntion relay - no change
Set up testing circuit from DkGr/white wire (from pin 3 on PCM clear connector)

Resolution
After driving the car with the test circuit in place I found that every time the car would stall and have no fuel pressure there would be no signal from the PCM on the Drk.green/white wire (clear connector pin#3).

I decided that there had to be a short in the wire somewhere from the PCM to the fuse box. So I tested the continuity and resistance in the wire. The wire tested good so I thought maybe with the engine under load there is an intermittent short. After dismantling the entire wiring harness from the PCM to the fuse box I find that the wire is in pristine condition. The connection from the wire to the fuse box is tight and solid. With the harness apart I checked the PCM grounds to distribution and they all read 0.0 ohms.

At this point I was worried that the PCM may be defective and the only option may be to replace it. This may get expensive!

Thinking
I sat wondering what might have caused this problem. There were no fuel pressure issues when I first purchased the vehicle. During previous troubleshooting I had disconnected the PCM to test the wires to the transmission (P0716). I made repairs to various wires and repinned the connector on the transmission. The transmission codes were gone but this is exactly when the trouble with the fuel pressure started.

One Last Try
Thinking that there may be a problem with the connector(s) on the PCM I removed them. Checking the continuity from the pins to the wires tested good. "Maybe I just didn't properly seat the connectors". At this point I removed the seal on both the blue and clear connectors at the PCM and reconnected them, using the bolts and making sure the connectors are properly seated. VOILA; I have put over 600 miles on the car without any stalling instances. The car runs absolutely perfect!

Lesson
If you are doing a substantial amount of troubleshooting on a vehicle and a new problem arises, retrace your steps because YOU MAY HAVE CAUSED A NEW PROBLEM!!!!

yeah i just had the same problem over this weekend. for me it ended up being the mass air flow sensor. the way you can check to see if it is that is to unplug the sensor. if the car starts and runs fine, then its the MAF sensor. but if the car still wont start then its another issue. what i did was unplug the MAF sensor. my car then started up just fine. but it was running on limp mode. so then i took off the MAF and cleaned it. you can use either MAF cleaner or brake parts cleaner. i used MAF cleaner. that didnt do the trick so one thing left and that meant the MAF was bad. So i went to a junk yard to find one, wasnt able to. then went to a used part place, got on, cleaned it, threw it on the car, and the car is now running just fine.