[BNaylor]

Don't feel bad, a lot of us have been through similar problems.

Do not be surprised if both MAF sensors already replaced are bad. I've seen people go through 3 to 4 of them to get one that works.

Another problem I have seen with consistent MAF sensor errors is a defective PCM module so unless it has been changed it cannot be ruled out. The reference voltage feeding the MAF comes from the PCM and the MAF will return specific performance values back in the form of frequency for the PCM to look at. Also, it would help to ohm out the wires from the MAF harness to the PCM and make sure there is continuity.

Further note: MAF sensors at the dealer or Autozone are not new but remanufactured so that explains the high failure rate. Also, make sure it is for your model '99 GTP. The MAF for a '97 -'98 will not work on a '99 properly. Parts stores have a tendency to mix them up and think all GP models are the same. That is not the case.

'99 GTP MAF sensor - AC Delco part #213-1617