# Mass Airflow Sensor Intermittent Failure



## Uakari (Aug 29, 2012)

1994 Sentra LE 1.6 manual 230k miles. 

A few months back, I got a CEL and it was throwing code 12(MAF). It was the original sensor, so I figured it best to go head and change it anyway. I bought a remanufactured Cardone MAF from a major autoparts chain. After installation, the code went away and she ran great. 

Two days ago I got a CEL and the car ran terrible. All the signs of a bad MAF. Sure enough code 12 again. I have read remanufactured or aftermarket MAFs such as mine can be not up to spec, but I can't justify paying 400 bucks for a Nissan made MAF with a car this old. 

I purchased a volt meter and manual and checked the voltages. I was getting 14 or so volts from terminal C on the harness connector, so it's getting power. Plugged the harness connection back into in to the MAF and check the sensor voltage and idle and higher rpm. On this car, backprobing terminal A is supposed to give a reading of anywhere under a volt, then rise to 1.1-1.4v with rpms. 

On first backprobe I got .029v, and upon revving it only got up to .032v. I thought faulty sensor. I disconnected the connector again to check for battery voltage at terminal C - still 14v. I plugged the connector back in and noticed my engine idled better almost instantly. I reprobed terminal A and it went from .o3v to the correct 1.3v upon revving. The CEL went off and it ran great again. 

CEL just came back on. Same MAF symptoms. Code 12 yet again. no voltage fluctuation on upon revving again. Steady at .03v. Wiggled connector around, tapped on circuitry housing on MAF. No change.

My question is, can a sensor such as this intermittently fail, or would it just fail and that's the end of it? I know very little about wiring. Could it be a faulty connection or a wire? Possibly ECU problem? No other problems with codes or running except for this issue. 

I should note that sometime after replaced the original MAF, I'd be going down the road and the CEL would flicker really faintly or fast like something small was happening but then it would disappear. I've never cleared the codes since then and never got anything but 12(maf). 

Side question, since my knowledge is limited with electrical, should I take it into a professional or is this something I could do without too much trouble if it is indeed a wiring/connector problem?

Thanks!


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## smj999smj (Jan 1, 2006)

Something I've seen on several mid-90's Nissans is a bad ground develope at the ground wire pin terminal in the MAS harness connector. It was most common on 95 Pathfinders, but I have ran across a couple of B13 Sentras and U13 Altimas that exhibited the same issue. Often those vehicles would run poorly until one would wiggle the harness connector on the MAS and suddenly the engine would surge and run well for a period of time. You should double check a wiring schematic, but I believe it was the white wire that was the ground wire. The fix was to use a pin tool (which came in a Kent-Moore terminal kit force shipped to Nissan and Infiniti dealers) to remove the ground wire and terminal from the harness connector for the MAS. The terminal was cut off, a supplemental 18 gauge ground wire was run from the negative battery cable end to the harness connector, which was spliced (or twisted together with) the white ground wire and a new terminal was installed on the wires' end. The new terminal was then installed back into the harness connector and re-attached to the MAS. Tie straps (and small conduit to protect the wire, if you had it) were used to secure the supplemental ground wire to make it look neat and keep it from dangling around. This is not to say that you don't have a bad MAS or other issue, but might be something you want to try, first.


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## Uakari (Aug 29, 2012)

Thanks! I will give it a go this weekend and let you know how it goes.


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