Air Flow Meter/Sensor: Testing and Inspection

CAUTION - Use only a digital multimeter when testing components and wiring. Use of an analog volt/ohm meter(VOM) may damage the engine control module.

1. Check ECM reference voltage to sensor:
a. Peel back rubber boot from air flow sensor harness connector.
b. Turn ignition key on.




c. Check for 5 volts between terminal 1 of harness connector and ground.
d. Turn ignition key off.

Engine Control System (DME M1.7, 4cyl. M42):

e. If voltage is not present or incorrect, check wring from ECM and check air flow sensor reference voltage output at ECM. Terminal 59.

2. Check air flow sensor potentiometer:
a. Remove intake air boot from sensor.
b. Connect a digital multimeter (ohms) across terminals 1 and 2. Swing air flow sensor vane through its travel range. Resistance should change steadily without interruption.
c. If any faults are found, the air flow sensor is faulty and should be replaced.
3. Check AT sensor resistance:
a. With harness connector disconnected at air flow sensor, check resistance across sensor terminals 4 and 5 of air flow sensor. Compare tests results to values in Table below. If any faults are found, the air flow sensor should be replaced.

14 +/- 2°F (-10 +/- 1°C) 7 - 11.6k ohms.
68 +/- 2°F (20 +/- 1°C) 2.1 - 2.9k ohms.
176 +/- 2°F (80 +/- 1°C) 0.27 - 0.40k ohms.