Air Flow Meter/Sensor: Testing and Inspection

CIRCUIT DIAGRAM





INSPECTION USING SCAN TOOL














HARNESS INSPECTION PROCEDURE

USING OSCILLOSCOPE





1. Run the engine at idle speed.
2. Connect the probe to the oscilloscope pick-up point as shown in the circuit diagram and check the waveform.

TROUBLESHOOTING HINTS
- If the engine sometimes stalls, try starting the engine and shaking the volume air flow sensor harness. If the engine then stalls, Incorrect or improper contact of the volume air flow sensor connector is the probable cause.
- If, when the ignition switch is switched ON (but the engine is not started) , the volume air flow sensor output frequency is any value other than zero, a malfunction of the volume air flow sensor or of the engine control module is the probable cause.
- If idling is possible even though the volume air flow sensor output frequency is deviated from the standard value, the cause is usually a malfunction other than of the volume air flow sensor .
[Examples]
- The flow of air within the volume air flow sensor is disturbed. (Air duct disconnection or clogged air cleaner element.)
- Incomplete combustion within a cylinder. (Malfunction of spark plugs. ignition coil, injectors, compression pressure, etc.)
- Incomplete combustion within a cylinder. (Malfunction of spark plugs. ignition coil, injectors, compression pressure, etc.)
- EGR valve - Improper adhesion of gasket.