Service Engine Light Code P0102

[ted-hurst]

I have a 1999 Chevrolet K2500 Suburban with the 7.4L and except for a K&N filter it's all stock. The truck has 100K and all maintenance has been done and when we coming back from a road trip, the truck started idling rough and the SES light came on. When I got home I scanned the computer and code P0102 (Mass Air Flow Circuit Low Input) recorded, I replaced the Mass Air Flow Sensor, checked the air filter (was clean and not over oiled), made sure all the ducting was tight, made sure the whole intake was clean and checked the wiring which looked good. I had not had any problems until this weekend and now it's running rough (Runs rough at first start up and at idle but drives okay through the rest of the rpm range). Where do I need to look next?

 

Thanks

Ted Hurst

[Haulin' 8.1]

Look for a vacuum leak anywhere in the intake system, even a stuck open PCV valve or loose manifold bolts. Your vacuum leak is feeding the engine air after the MAF somewhere and it should be noticiable considering it's setting a code. A crack in the ducting or missing hose will do it. Don't forget the crankcase is part of the PCV system and is fed by the breather tube sealed to the intake duct. If the crankcase isn't sealed air will flow into the intake system unchecked by the MAF from the opening. Even a missing or loose dipstick would cause this.

 

Vernon

[flounderpounder115]

Look for a vacuum leak anywhere in the intake system, even a stuck open PCV valve or loose manifold bolts.  Your vacuum leak is feeding the engine air after the MAF somewhere and it should be noticiable considering it's setting a code.  A crack in the ducting or missing hose will do it.  Don't forget the crankcase is part of the PCV system and is fed by the breather tube sealed to the intake duct.  If the crankcase isn't sealed air will flow into the intake system unchecked by the MAF from the opening.  Even a missing or loose dipstick would cause this.

 

Vernon

 

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[ted-hurst]

Quick question, the low circuit input refers to the air coming in and not voltage? I checked the PVC and dipstick and intake routing and didn't see any problems. Is there a diagrahm showing the intake lines and hoses?

 

Thanks

Ted

[ted-hurst]

The problem was the wiring harness by the firewall over the transmission. I talked to the local GM dealer and one of the mechanics first suggestion was the wiring harness. This must be a common thing because he knew right where it was and didn't take him long to fix it. The sensor side of the O2 sensor (not the heat side) had a shorted wire which caused the ENG-1 fuse to blow. The sensor side is not in the wiring schematic so I only checked the heat side.

 

Ted