Update: Unplugging the MAF works. MAF reference pin is in the correct spot. However i get no response from the sensor with key on engine off. Bad MAF? it was just working that morning.
Update: Unplugging the MAF works. MAF reference pin is in the correct spot. However i get no response from the sensor with key on engine off. Bad MAF? it was just working that morning.
My schematics are for a 2002 Express Van 5.7 Liter. I've used the schematics to build new Stand-Alone harness for both the Vortec 5.7 and Vortec 7.4 (1996 - 1999).
The sensor part # information below is from RockAuto: Same sensor part numbers, same wiring. There might be more than one source in the '0411 for 12 volts and sensor reference. There is only one place the sensor signal can be wired to. Check the sensor connector wiring, by unplugging the connector from the sensor ... Key On / Engine Off measure the pin voltages on the unplugged connectors.
The MAF will send a signal Key On / Engine Off if you have air flowing through it, like a blast of compressed air. Caution, do not BLAST compressed air next to the MAF, about 6" away from the MAF is safe.
dave w
2002 Express Van 5.7
CKP – SMP PC123
CMP - BECK/ARNLEY 1800750
1998 C2500 7.4
CKP – SMP PC123
CMP - BECK/ARNLEY 1800750
I can get it to fire up with the MAF unplugged. So I dont think CMP/CPK sensors are bad or mispinned. I'll check voltage later tonight when it cools off. I'll also visually inspect the maf to see if its dirty. I find it hard to believe the MAF is dead as it worked 8 hours earlierOriginally Posted by dave w
Update: MAF connector gets 12v with key on. Connector also has a good ground. Connector is showing 5v reference. There is continuity between reference line at connector and C2 31. So....bad MAF? Could the PCM have a fault in the tune?
It's interesting the engine runs without the MAF plugged in. So, I'm wanting to understand correctly, with the MAF plugged in the engine won't start?
lMAF sensors are the same part numbers, 2002 Vortec 5.7 liter and 1998 Vortec 7,4 liter.
The starter flash I use for the '0411 Vortec 7.4 liter conversion is a modified 2002 Express Van 5.7 liter flash. Basically a 5.7 liter flash with 7.4 fuel, air (displacement), & spark parameters.
dave w
Correct. It will run, and will pretty well with the MAF unplugged. The PCM was supposed to have been flashed accordingly by Jeff. So I dont know if the MAF is actually bad, bad tune parameters or what. But the pcm isnt showing any response from the MAF. It's not showing g/s or MAF frequency.
The MAF wire is in fact getting hot, so it is still receiving power and at least functioning.
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