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OBD II P0102 - Replaced MAF, But Chk Eng Still On

Hi all:

I could use a bit of advice. I have a 99 Pontiac Grand Prix with 38000 Supercharged engine. The check engine light came on with code P0102 MAF Circuit Low Input. I bench tested the MAF sensor. It varied the output voltage signal, but not by much. I purchased a new MAF sensor and bench tested it as well for comparission. It varied the voltage signal by significantly more. I thought I had found the problem. I installed the new MAF sensor. Then I disconnected the battery to clear the old code, reconnected the battery, and then started the car. The Check Engine Light is still on. What else should I be looking at? Any other advice appreciated? Thanks in advance.

Reply to
jgrakla
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I'm not sure about every model, but with some, disconnecting the battery does not clear the error codes. The OBDII tool has to send a reset command to the controller.

Reply to
Paul Hovnanian P.E.

P0102 could mean that there is inadequate flow through the MAF, possibly due to a restriction inside it, an engine vacuum leak, etc. Assuming you didn't get a bad MAF out of the box, you could check the electrical basics as well. Your MAF generates a frequency, not a varying voltage, so your bench testing method was probably flawed.

First, check the pink wire for full battery+ voltage. Then check the Black/White wire for ground. Finally, test the yellow wire with engine idling and MAF connected: backprobe the yellow wire with positive lead, ground the neg lead, and set your DVOM to read frequency. You should see about 3000 Hz at idle. Below a certain threshold (about 1000 Hz) the PCM will flag a code P0102. If the freqency is good at the sensor, it should be good at the PCM given the 5v. reference circuit design used. This is where an oscilloscope would better show how clean the signal is and the low and high voltage points, but if you don't have a scope this sentence is academic.

Toyota MDT in MO

Reply to
Comboverfish

alot of GM vehicles with the obdII system will NOT clear code by unhooking the battery, you need a scan tool of some sort to clear the code.

Reply to
martinsauto

alot of GM vehicles with the obdII system will NOT clear code by unhooking the battery, you need a scan tool of some sort to clear the code.

Reply to
martinsauto

Reply to
philthy

Hi all,

Thanks for the good advice. I was finally able to get the error codes cleared. I tried disconnecting both positive AND negative battery cables. Previously I had just disconnected positive cable and let the car sit for about 15 minutes. Upon reconnecting and starting up, the check engine light finally stayed off. Not sure if it was a matter of both cables being disconnected, or I had read that some models require three good starts before self clearing a condition code.

Reply to
Jason Graklanoff

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