1999 GTP Service Engine Soon Light

[glss421]

1999 GTP with 91,000 miles

The service engine soon light comes on intermittently.

I had the code checked 3 different places and it comes back as the MAF sensor.

I changed the MAF sensor and the car was fine for a while but then the light came back. I had the code checked again and this time 2 codes came back as the 02 sensor and the MAF sensor.

Also when the light is off the car runs like a dream, but every once in a while it will have a rough start, sputter a little, and light comes on. The rough idle smooths out when the car gets going but the light is still on for 2 days before it shuts off again for another 2.

Where do I start?

[BNaylor]

Is your GTP stock or modded? Any CAI/FWI? What was the specific trouble code(s)? Post it.

What brand MAF sensor was used? Was it a new GM, new aftermarket or a used/remanufactured? Not uncommon to get re-ocurring MAF sensor faults with aftermarket or reman.

Also, is the throttle body inlet screen installed or removed?

[glss421]

I did install a remanufactured MAF and I think that's the problem because when i First start it up, I hear an unusual whine coming from the air box...as if an excessive amount of air is being sucked in.

Does that make any sense?

[BNaylor]

Many of us had bad luck with reman MAFs. What tool did you use to secure the two screws? Should use a tool with a Torx T20 tamper proof bit.

Here is source for a new GM MAF sensor.

Click here

[glss421]

I have been using a tamper proof bit, but on one of the screws, the metal peice in the center, which I'm assuming makes it tamper proof, broke off. It's secure but I don't see it have any affect on the performance of the sensor.

Anyway, I exchanged the MAF sensor for another remanufactured one and there are no codes and the car runs great.

Thanks for the help.

[lil_nages22]

While on this topic, I have replaced my MAF sensor on my 2000 GTP, but while replacing I came upon the problem of maybe a wire issue, mainly the harness that connects to the MAF sensor. Is there a way to fix this issue?

I am taking the car to a dealer soon anyways because of a safety recall but I would like more than one opinion. Thanks.

[BNaylor]

Originally Posted by lil_nages22

While on this topic, I have replaced my MAF sensor on my 2000 GTP, but while replacing I came upon the problem of maybe a wire issue, mainly the harness that connects to the MAF sensor. Is there a way to fix this issue?

Is it any of the 3 wires in the harness or the electrical connector? You can get a replacement electrical connector.

[lil_nages22]

That I am not sure of. What would be the procedures for fixing each problem?

[BNaylor]

To start you'll need a DMM (multimeter) and the GM wiring diagrams for your year and engine size. At the MAF electrical connector you can check for the PCM 5 volt reference signal at one of the pins. Do a wiggle test on the harness and connector. Next you can check the ground input at the connector. See if meter reads a short to ground in the ohms position. On the output signal you can ohm out from the pin to the input at the PCM module. There are two 80 pin connectors at the PCM. Wiring diagram should show the input pin and wiring color coding.