MAF testing

[Warren]

I have a '99 Protege with 1.8L engine.

Is there a way to test the MAF sensor?

I don't want to buy a faulty used part, and don't want to go through the expense if the existing part is still ok.

What is the exact part number for the part?

[goldstar]

Welcome to the Forum.

Since no one else has responded to your question, I'll try to provide some information although this material comes from the '02 FSM so may not be completely relevant for your car.

The first step is a visual inspection. "Visually inspect for damage, cracks, terminal bends and terminal rust on the MAF sensor. If any of the above is found, replace the MAF sensor."

The next step is to check the voltage reading at PCM terminal 88. If out of spec, the MAF wiring harness must be checked for a short or open condition and repaired if necessary. If no short or open condition is found, replace the MAF sensor.

VOLTAGE LEVELS
"The PCM monitors the input voltage from the MAF sensor. If input voltage at PCM terminal 88 is below 0.86 V, PCM determines that MAF circuit has a malfunction." If this is the case, the MIL will illuminate (P0102, MAF circuit low input). This signifies either MAF sensor malfunction or short or open in wiring harness.

"After ignition key is turned on, if input voltage at PCM terminal 88 is above 4.90 V, PCM determines that MAF circuit has a malfunction." Again, the MIL will illuminate (P0103, MAF circuit input high). And again, the problem lies either in a faulty MAF sensor or a short or open in the wiring harness.

The FSM explains how to check the wiring harness.

ONE FINAL POSSIBILITY
If the MIL illuminates and reads out as P0101 (MAF circuit range/performance problem), this indicates that the PCM has determined that the mass intake air flow amount is either too low or too high as a function of RPM or throttle opening angle. According to the FSM, the possible causes here are:
MAF sensor malfunction
TP sensor malfunction
Electrical corrosion in MAF signal or return circuit
Voltage drops in MAF signal or ground circuit

I hope this helps.

Happy Motoring!

[Warren]

I'll have a look at the MAF voltages.

Do you have a vacuum hose diagram?

Thanks!

[goldstar]

There is a vacuum hose diagram on a placard under the hood on my car. Of course, the FSM also provides this info. I don't have a scanner so I can't reproduce it here. Perhaps another Forum member can help you out with this. Good luck with your troubleshooting.

Happy Motoring!