Got a MAF sensor error code. Voltage output measurements for three different conditions indicate sensor working properly. What are the chances it is the cable or electronic engine control? Or, intermittent MAF?
Voltage output measurements for three different conditions indicate sensor working properly.
Based on what technical reference?
I would also keep in mind that the speed of the MAF output change, relative to the actual airflow change, may also be significant. In other words, a lazy sensor could flag an error.
As requested, posting the actual code(s) would be very helpful.
One long flash, two short flashes
Based on Haynes Repair Manual (yeah, I know, probably not the best source but I found no other sources). It is an A1 Cardone unit. Part number 74-10045.
Intake air thermistor is 2000 ohms at room temp, 7000 ohms in ice water, and 1500 ohms when I blow hot breath on it.
With the ignition on, engine not running, output is 0.5 volts
With engine idling, output is 1.35 volts
When engine rpm is increased and held, the output rises, then falls. Doesn’t get over 4 volts, and falls back to something over 2 volts; if I need a more precise output voltage to rpm, I will have to measure.
One long flash, two short flashes. No other error codes. I did a visual inspection with high intensity lamp and magnifying glass; no obvious visual problems. The integral screen was very clean.
DTC code 12 is for: “[Trouble with the] air flow meter”. At least the code gets you in the ball park.
Here are voltage charts and stuff on the MAF (air flow meter): http://www.aa1car.com/library/maf_sensors.htm
The MAF (Mass Air Flow sensor) voltage shouldn’t fall off if the air flow remains constant. A poor connection can cause voltage to drop.
Somebody had a problem with the MAF, before, evidenced by it being a replacement unit (aftermarket). Now, we can’t know, "Why?"
Check the supply voltage, to the MAF. It should stay at a certain value, depending on the car make (maybe 5 volts).
How old is Miss. Altima? How big is her engine, and is it V shaped?
Although the MAF appeared to be working, I replaced it with a rebuilt ($240…OUCH!)and it seems to have fixed the problem. Apparently, they can drift out of specification, that is the only conclusion I can form.