Problem with my 04 Grand Prix GT2

I am having issues with my 04 Grand Prix also. I am leaning towards the fuel pump but am a little leary about just dumpng more money into it. So far I have changed the MAF Sensor, Spark Plugs and wires, coils, Checked and cleaned fuel filter, changed MAP Sensor, o2 sensor are a little over 2 years old, changed oil and filter, and the thermostat. Any idea what could be the problem with this dinosaur?
Here is the freeze frame data:
Fuelsys1= OL_Fault
Fuelsys2= N/A
Load_PCT (%)= 16.9
ETC (°F)= 180
SHRTFT1 (%)= 0.0
LONGFT1 (%)= -25
MAP (inHG)= 19.8
RPM (/min)= 1577
VSS (mph) 55
MAF (lb/min)= 3.931
TP (%)= 23.1
Fault Codes= P0132, P0135, P0141
Catalyst= INC
Evap Sys Mon= INC
Oxy Sen Mon= INC

So Randy, are you working on other people’s car for money without actually being trained as a mechanic and coming here for us to tell you what to fix??

Again… no year, no engine type, no mileage…

Your repair technique is identical to the F150…throw plugs, coils, MAF and MAP, oil and filters… at the problem with no fix.

You’d probably save money taking your cars to an actual mechanic to have them repaired.

Your codes indicate a bad upstream O2 sensor in Bank 1, AND a bad O2 sensor in Bank 1 downstream. Since you replaced them 2 years ago, either they were cheap junk O2 sensors or the wiring harness is damaged or the ECU has failed.

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That really stands out . . . what are the fuel trim values for Bank 2?

How does the car run, btw?

No idea what that means, but it looks ominous. Assuming that’s not the problem, concur w/advice above, the -25% long term fuel trim is a big clue. That means the computer, comparing how much fuel it would deliver based on the intake airflow as measured by the MAF sensor, the computer is finding it necessary to reduce the amount of fuel delivered to the engine (or that bank of the engine) by 25 % in order that the O2 sensor reads the correct 13.6/1 mixture. Likely problems

  • Faulty MAF sensor
  • Faulty O2 sensor(s)
  • Faulty injector(s) (stuck open)
  • Spark problem is causing unburned fuel to pass through engine & into exhaust

If I had that problem I’d start by looking at the signals from the O2 sensor, pre and post cat, at a time when the fuel trim is out of whack. BTW, when the long term ft is -25 and the short term is 0, that means at that time the fuel trim is ok, but before the short term must have been out of whack as well. So best to choose a testing time when both short and long term are significantly negative.

Might be necessary to swap injectors, coils etc from bank to bank (assuming you have more than one bank) as diagnostic tests.

Don’t ignore the OL_Fault, first priority is to identify if that’s an actual problem.

No they are mine, and I don’t take older cars to a repair shop. Just so happens they have the somewhat of the same issue. No I am not a trained auto tech, I was a diesel mechanic I’m service for 14 year but as you know working on vehicle with electrical systems is quite different that working on a diesel engine with bare bones electronics. Grand prix is fixed btw. Guess I know better next time than asking anyone on forums for advice. No worries though I know not to ask for advice next time.

This Forum has quite a few very experienced mechanics that post good advice as they can with the limited info posted . You had 2 threads with 2 different vehicles . You could have made yourself a little more clear as what you needed .

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The freeze frame data indicates the Fuelsys1 is in the Open Loop mode.

The ETC indicates the coolant isn’t reaching the proper temperature.

The OEM thermostat for your vehicle is 195 degree.

And the catalyst, Evap system, and O2 sensors are incomplete.

So, either the battery was disconnected or codes were erased recently.

So, from what I read, the thermostat is stuck open and the computer is staying in the open loop mode.


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And we know better than to ask you what engine is in the car and the miles on it. I guess it would be useless to ask what actually fixed it as well


One of the things he did. Although I doubt even he doesn’t know which one.

Ideas are what internet forums such as this might provide; specific advice is best obtained from the staff of a trusted repair shop.

Some years ago I was looking for some ideas on better ways to replace my Corolla’s starter motor. It’s a bear doing it the way the shop manual says. Would work ok if car was on a lift, but very difficult while laying in driveway under the car, as a diy’er does the job. I signed onto an internet forum, a fellow for England told me how he does most of that work from above, working in the engine compartment. Very helpful. It wasn’t advice, but it was a very useful idea.