MAF sensor electrical from fuse box

[TwistR]

Hello, I have a 96 K2500 with the 5.7 Vortec. It's running rough and idles up and down on start and hiccups on the highway; engine code P0102. I cleaned the MAF but no change. The engine does better if the MAF is disconnected, and my mileage takes a nosedive. I checked the electrical feed and ground is good, the sensor power is good at 5V, however the wire for the constant 12V is dead.

I tried tracing the wire, but it goes into a wire bundle then to the ECM or fuse box. I'm thinking next steps are to test the wire end to end continuity and check if the ECM or fusebox is putting out 12V. Does anyone
know or have an electrical diagram to point me to the wire connectivity on the ECM or fusebox side of the electrical?

I'm a DIY and I'm learning so any and all help is appreciated.

 

[1997]

welcome, what part of BC?

this might help you out, thank HATZIE.

https://www.gmt400.com/threads/88-95-service-manuals.43575/

unfortunately no 96-97, but i'm thinking if the color of the wires match the 98 diagram, it might help you out.

 

[stutaeng]

Hello, I have a 96 K2500 with the 5.7 Vortec. It's running rough and idles up and down on start and hiccups on the highway; engine code P0102. I cleaned the MAF but no change. The engine does better if the MAF is disconnected, and my mileage takes a nosedive. I checked the electrical feed and ground is good, the sensor power is good at 5V, however the wire for the constant 12V is dead.

I tried tracing the wire, but it goes into a wire bundle then to the ECM or fuse box. I'm thinking next steps are to test the wire end to end continuity and check if the ECM or fusebox is putting out 12V. Does anyone
know or have an electrical diagram to point me to the wire connectivity on the ECM or fusebox side of the electrical?

I'm a DIY and I'm learning so any and all help is appreciated.

All of the fuses are okay?

 

[TwistR]

All of the fuses are okay?

As far as I can tell, I was noping to identify the specific fuse for this sensor. I'm guessing the 12V is out of the fuse box and thee 5V is from the ECM, but I'm just guessing.

 

[JWOK]

I have the Chilton manual in front of me (pretty poor wiring diagrams), but it shows the MAF 12v feeding from ENG-1 20A fuse in the under hood fuse box. This circuit shows to be common with O2 heaters, canister purge solenoid, and ECM A4.

 

[Pinger]

I have the Chilton manual in front of me (pretty poor wiring diagrams), but it shows the MAF 12v feeding from ENG-1 20A fuse in the under hood fuse box. This circuit shows to be common with O2 heaters, canister purge solenoid, and ECM A4.

Haynes manual shows the same - a pink wire - possibly one of two - at the fuse box.
Signal wire is yellow and goes to PCM.

 

[TwistR]

I have the Chilton manual in front of me (pretty poor wiring diagrams), but it shows the MAF 12v feeding from ENG-1 20A fuse in the under hood fuse box. This circuit shows to be common with O2 heaters, canister purge solenoid, and ECM A4.

Yes, I used the manual posted above, wish I'd checked your post before I spent 2 hours pouring through the manual. But it's good to know I'm on the right path. It's snowing like crazy so I will check the connectivity later, but I have to assume that if that fuse was bad or if the power was dead at the fusebox that I'd have all sorts of codes. That isn't the case through, just the P0109 which is the MAF sensor low frequency. I do get 5V at the sensor but no 12V at the power (pink). I did find the solder point (s108) page 1710 of the manual "The engine harness, approximately 11 cm from the ignition coil breakout, toward the starter solenoid". Hopefully that's all it is. Thanks for posting.

 

[TwistR]

welcome, what part of BC?

this might help you out, thank HATZIE.

https://www.gmt400.com/threads/88-95-service-manuals.43575/

unfortunately no 96-97, but i'm thinking if the color of the wires match the 98 diagram, it might help you out.

Thanks the manual helped a lot. For others reference I used the 1998_GMT-98_CK-3_SERVICE_MANUAL-VOLUME_3_of_4.pdf

Pages:
1683 DTC code P0102
1696 MAF Schematic
1759 Diagnostics steps

I get 5V at the sensor, it's the pink wire 12V that is dead. The solder point is S108 and location is referenced on page 1710.

I also found a good page on the pin-outs on the ECM: https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/pcm-connector-pin-outs-1996-1997-page-4

Looks like it will be pretty simple I hope. I'm in the Kamloops area.

 

[TwistR]

First, thanks everyone for the help. I watched a video on replacing the ignition coil and worked my way to solder point S108 referenced above. Replaced the wire running to the 12v on the MAF sensor connector. Runs like a charm now.

Side Note: While checking my fuses, one 20A fuse looked good and was active, however it had over 800 ohms of resistance so I replaced it. Also my voltage lead on the multi-meter went bad while doing final testing. I almost ripped the wiring out again, glad I checked on the battery first.

Cheers!

 

[1997]

good to hear you got it sorted.