'99 P0101

Can anyone explain what is exactly happenening when code P0101 is stored (engine light is on)? Is a new MAF sensor the right move?

'99 AWD, 4.3l, W in VIN, 105K miles.

Thanks!

The MAF is not reporting to the PCM when there are ignition reference pulses. Instead of replacing the MAF on a hunch, make sure it has 12V, ground, and measure the output frequency right at the sensor.

Blue Bowtie, I have a universal voltmeter (the kind you get from Lowe's and can use in your house). Can I make the output frequency check with that device?

Also, when I have had MAF sensors go on other GM vehicles I owned, the service engine light came on and stayed on with the MAF code stored until I replaced the sensor. What my vehicle is doing is this - the engine light comes on with P0101 stored. I'll drive for awhile and the light will go off and may stay off for a day or so - then it comes back on. If the MAF sensor is shot, would I have an intermitent engine light?

The vehicle seems to run the same with the light on or off. Also, last night I unplugged the harness to the sensor with the van running and it stalled out.

Thanks!

Unplugging the sensor with your results seems to indicate that the MAF was indeed sending signal to the PCM. That means the MAF is not dead (or at least, not totally). I've had a few of the TB mounted MAFs with marginal connections right at the electrical socket and in the harness connector. Make sure the connector pins are clean, the socket contacts are tight (not sprung open) and the wires are intact. If you wiggle the harness connector while the engine is idling, does the engine stumble?

Have you tried to use a spray cleaner through the MAF screen to clean the elements? Make sure it is an electrical cleaner, and not a carburetor cleaning solvent, since the latter can be a bit too aggressive for the insulation.

Quick update...

I fooled around with this and couldn't get anywhere. Replaced the MAF sensor and the light has not come back on.

Thanks for all of the input!