Summit Vista FWD L4-1795cc 1.8L SOHC (1992)
Air Flow Meter/Sensor: Testing and Inspection
To test the Air Flow Sensor, located inside the air cleaner housing proceed as follows.
Scope Pattern
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.
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 7 (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 7: AFS output
2.
Measure the frequency across terminals 5 and 7.
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 pre-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 7 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.
