Code 12

Air Flow Sensor Circuit:

To test the Air Flow Sensor, located inside the air cleaner housing, proceed as follows.

Air Flow Sensor, Test Hook-up:

VOLTAGE TEST
1. Connect a voltmeter between terminal 6 and 3 of the Air Flow Sensor (AFS) connector.
Terminal 6: Sensor ground
Terminal 3: AFS output
NOTE: To test pins do not remove the connector, instead insert a straight pin or needle from the back side of the connector to access the pin.

2. Warm the engine and bring it to a normal idle.
3. Measure the voltage of terminals 6 and 3 at both RPMs, to determine if it is within the given value.
Standard Values
Engine speed (rpm) Output voltage(V)
Idling to 3,000 RPM......2.7-3.2
Voltage should vary when racing the engine.

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 6 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 6: Sensor ground
Terminal 3: AFS output

2. Measure the frequency across terminals 6 and 3.

Standard Values
25 to 27 - 33 Hz at 750 rpm
67 to 60 - 80 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.