Federal or Canada Emissions

Volume Air Flow Sensor:

Symptoms
Engine Stalls occasionally, crank engine while shaking the air flow sensor harness. If the engine stalls, suspect a bad connection at the air flow sensor.

If the air flow sensor output frequency is other than - when the ignition switch is turned on (but the engine is not turning, suspect a faulty air flow sensor or engine control module.

If the engine can be run, even though the air flow sensor output frequency is out of specification, suspect problem is not air flow sensor.

Location
Air Flow Sensor located inside the air cleaner housing proceed as follows.

Test Connection:

Oscilloscope Testing Procedures
1. Run engine at idle speed.
2. Engine coolant temperature should be at: 85-95°C (185-205°F), with no electrical accessory loads on.
3. Connect the input probe of the oscilloscope, to the pickup point shown in the circuit diagram, and check the wave form.
If scope pattern is not as depicted in image, continue with the rest of the test procedures before replacing the assembly.

Normal Wave Forms:

Abnormal Waveform:

Frequency Testing Procedures
1. Warm engine. Coolant temperature should be at: 85-95°C (185-205°F), with no electrical accessory loads on. Connect a Frequency counter (HERTZ counter) between terminal 5 and 3 (do not remove the connector, instead insert a straight pin or needle from the back side of the connector) of the Air Flow Sensor (AFS) connector.
Terminal 5: Sensor ground
Terminal 3: AFS output
2. Measure the frequency across terminals 5 and 3.
Standard Values
25 to 50 Hz at 750 rpm
70 to 100 Hz at 2,000 rpm
Frequency increases as RPM increases

NOTE: If the air flow sensor fails, the intake air volume cannot be measured and as a result, normal fuel injection control is no longer available. However, the vehicle will run using the programmed value.

Harness Test
1. Disconnect the air flow sensor connector and turn the key to the ON position.
2. Using a voltmeter, measure the terminal voltage between the harness connector terminal 3 and ground.
Voltage: 4.8 - 5.2 Volts.
3. Using a voltmeter, measure the power supply voltage between the harness connector terminal 4 and ground.
Voltage: System voltage.
4. Check for continuity of the ground circuit of the air flow sensor, between the harness connector terminal 5 and ground.
Continuity: Should exist

If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, clear the trouble codes and road test the vehicle to confirm that the repair has corrected the problem and the code doesn't return.
If the same trouble code reoccurs, it is possible that there is an intermittent failure of the component or the ECM. Check for looseness at all harness junctions and test for an intermittent failure.