|Step 1 - Throw antiquated worthless system tests in the Bentley boat anchor in the trash.
1 unfolded safety pin, 2 jumper wires, and a DVOM.
Looking from the FRONT of the car to the BACK of the car... there are 4 wires off the MAF.
Good, unhook the MAF the connector.
Ground one side of your meter to the intake manifold.
(NOTE IT WILL STAY GROUNDED FOR ALL THE TESTS IN THIS SECTION!)
Take your safety pin and stick it into the FRONT of the MAF harness. Insert it into PIN 3.
Turn the Ignition ON in the car. DO NOT START THE CAR, JUST TURN THE IGNITION ON!
You should get 12 volts or higher. (Battery voltage). If not, check the ECU and harness wires back at the ECU. This is the 12 volts sent to the MAF from the ECU to power the MAF.
TURN THE CAR OFF.
Set the meter to read OHMS. LEAVE THE CAR OFF!
Next, move the safety pin to pins 1 and 2. (do one at a time, same test…)
These are the internal grounds for the sensor, power and signal. You should get LESS then 3-4 ohms on BOTH pins. If you get MORE then 3-4 ohms check the harness for breaks or opens, or the connector at the ECU for damage.
Last test, Pin 4.
MAF signal return to ECU.
Remove your safety pin from the MAF sensor harness.
Set the DVOM to read Volts DC again.
Plug the MAF sensor back in.
BACKPROBE the RED wire, PIN 4 on the MAF sensor. Use the safety pin to SLIDE the probe down the wire into the connector base. The point is NOT to break the wires insulation.
START the CAR. Yes, RUN the CAR. Yes, with the safety pin JAMBED into the wire harness.
Voltage at IDLE should be around .9 volts DC.
Use this handy, dandy chart as a guide:
Idle .9 volts.
2000/3000 RPM 1.5 volts.
3000/Wide Open = up to 3.8 volts.
Note the speed at which the MAF can respond to the changes and airflow.
If your MAF is slow, or lazy, or does not match these values. Good chance its bad.
I was unable to get a power voltage reading on pin 3 while testing my MAF at first, but then I did a little research and found that on later model OBDII cars that the engine must be running versus the ignition being just switched to On to get a power reading. This could have saved me about an hour if I knew this! Dan J Reed, I implore you to make a modification to your MAF DIY test and mention this to save someone else the trouble in the future.
Modified by Dan J Reed at 2:09 AM 11-2-2007