DTC 12

CIRCUIT DIAGRAM





USING MULTI-USE TESTER





USING OSCILLOSCOPE

Steps 1-2:

Steps 3-4:

HARNESS INSPECTION



OPERATION

AFS is integrated in the air cleaner to measure the intake air flow rate by using the Karman vortex phenomenon. The Karman vortexes are asymmetrically and regularly generated downstream from the triangular pillar when the pillar is placed in the air stream. The generation rate of vortexes is proportional to the air flow rate.

AFS uses ultrasonic waves to convert the generation rate of vortexes into the pulse signal which is proportional to the air flow rate, and inputs the signal to ECU. ECU calculates and determines the standard injection time from the intake air flow rate signal and the engine revolution speed signal (crank angle sensor signal).

On the turbo vehicle, to eliminate the measurement error of the intake air flow rate influenced by the turbo system during deceleration from high speeds (high load) in the turbo supercharging state, another circuit is added to send the reset signal from ECU to AFSI. When the reset signal is inputted, AFS resets the modulator to select the circuit which attenuates the turbo noise.

TROUBLESHOOTING HINTS

1. If the output frequency of AFS rapidly varies greatly, it may result from an improper contact of the AFS connector.

2. If the AFS output frequency is excessively high or low, check the air cleaner element.

3. If the AFS output frequency is high, the engine resistance may increase or the compressed pressure may leak.

4. If a wire is broken in the filter reset circuit of a turbo vehicle. shock may be felt during deceleration from the high speed (high load) operation.