Need help troubleshooting Maf on Avalanche

[Mobile Chassis Dyno]

Got a customer with no maf signal coming out of it. He has had to the dealer twice and they keep putting maf's on it. LOL I hooked the scanner up to it and we have 0 hertz coming from the maf. However, the IAT portion of things is working. It is a 02 model with the big V8. (8.1 maybe?) Any suggestions on where to get a wiring diagram or what pins I should be testing on the PCM? Where is the PCM located?

Thanks for helping out this Ford guy in advance.

[n0dih]

I would presume it has a MAF fault? Has the vehicle been tuned before and the MAF tuned out (aka, Speed Density mode)?

Yes, it is the 8100 Big Block Chevy if it is a 2500 Avalanche.

If none of the above I would be looking at verifying the MAF wiring. Throwing customer's hard earned cash at fault codes is NO method for troubleshooting (makes me wonder about some of the mechs these days....)

1. Verify fault/failure mode
2. Verify data/signal from device (backprobe the MAF signal with an oscilloscope or a frequency counter) at the MAF and the PCM.
3. Either MAF, wiring, or PCM (hardware or software) is the fault. OR, of course, there is no air coming through the MAF....

[jimmyblue]

On the Camaros the MAF being dead, seems most often to be
the ENG SEN fuse blown. Don't know about the wiring on this
truck. The IAT is separately sourced from the PCM (on my car).
MAF needs 12V power feed and the output has a soft pullup to
5V. Both of these voltages should be on the open connector at
key-on.

[12secSS]

On the Camaros the MAF being dead, seems most often to be
the ENG SEN fuse blown. Don't know about the wiring on this
truck. The IAT is separately sourced from the PCM (on my car).
MAF needs 12V power feed and the output has a soft pullup to
5V. Both of these voltages should be on the open connector at
key-on.

I got $20 on it being this. I have had a few cars with that exact problem (either blown fuse or attempt at disabling the ABS), once fixed the MAF was back.