Dan J Reed
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7-26-2004
15270 posts

Stinkville, NJ
95 Golf Sport, 1987 VW Vanagon, 98 Jetta GLS

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 DIY - MAF Testing. Reply to this postEdit this post

Step 1 - Throw antiquated worthless system tests in the Bentley boat anchor in the trash.

You'll need:

1 unfolded safety pin, 2 jumper wires, and a DVOM.

Got them?

Good.

Lets begin.

Looking from the FRONT of the car to the BACK of the car... there are 4 wires off the MAF.

See them?

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!

 (OBDII NOTE!! SEE BOTTOM OF PAGE!!!)

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.


Modified by Dan J Reed at 10:46 PM 6-15-2007


IMPORTANT NOTE!  HEY DUMMY!!  THIS IS FOR AN OBDI CAR! OBDII CARS ARE TESTED THE SAME WAY.. EXCEPT THAT AT THE MAF IS NOT POWERED UP UNTIL THE CAR IS RUNNING!

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