Greetings.
My wife's beloved still shiny '99 GT keeps popping up a recurrent pair of codes. The first time, it was just the PO102, MAF sensor low output. I replaced the sensor, cleared the code. But when I re started the car, it popped right back up.
The car has the symptoms of a bad MAF, unstable idle, hesitation off idle on acceleration, and some times (never happens to me but happens to her) it does not want to re start hot. Used to do 300 miles to a tank in the city and is now down to about 260.
I exchanged the sensor today as it was under warranty. Again, change sensor, clear code, start car, BAM! 15 seconds after you start it, the MIL comes back on.
I finally bought a scanner, an Actron CP9580, rather than the code reader I had. So I can get real time data. I have not had much time to work with it yet but it will record, freeze frame and graph if needed. However, I did use the CODE CONNNECT feature which leads to common repairs for this code, and beyond replacing the sensor there is repair sensor wiring harness and repair sensor ground, replace ignition switch (don't know how that would relate) and replace PCM.
Anyway, back to the problems- you can clear the codes with the engine running, drive all over with no appearant issues, but when you shut the car off and re start, these two come right back up.
Now, I don't have a factory manual with a nice engine harness diagram but in my experience with electronic engine controls (diesels) a lot of things can be traced back to a bad common ground in a harness plug or an abraded/corroded connection.
Also, I have a coolant level switch I gave up and disconnected due to erroneous readings, and the exterior temp reads low by 15* and it all used to work fine.
The car has 210,000 on it, I repaced the original MAF at about 160,000, had NO trouble until last month at 108,000, then today as mentioned in the first paragraph I exchanged it to no avail.
Does anyone have any thoughts on this or have access to a wiring diagram for the engine? This whole thing seems to me to be a harness or connection problem. Want to get my poncho back to normal!