Air Flow Meter/Sensor: Testing and Inspection

Volume Air Flow Sensor:

TROUBLESHOOTING HINTS
Hint 1: If the engine stalls occasionally crank the engine and shake the volume air flow sensor harness. If the engine stalls poor contact of the volume air flow sensor connector is suspected.

Hint 2: If the volume air flow sensor output frequency is other than 0 when the ignition switch is turned ON (but not starting the engine), faulty volume air flow sensor or engine control module is suspected.

Hint 3: If the engine can be run idle even though the volume air flow sensor output frequency is out of specification, troubles are often found in other than the volume air flow sensor itself.

[Examples]

1. Disturbed air flow in the volume air flow sensor (Disconnected air duct. clogged air cleaner element)
2. Poor combustion in the cylinder - Faulty spark plug, ignition coil, injector, incorrect compression pressure, etc.
3. Air leaking into the intake manifold through gap of gasket etc..
4. Loose EGR valve seat.

Air Flow Sensor:

NOTE: Check to be sure that cycle time T becomes shorter and the frequency increases when the engine speed is increased.

EXAMPLES OF ABNORMAL WAVE PATTERNS

Example 1 - Sensor interface malfunction

Wave pattern characteristics
- Rectangular wave pattern is Output even when the engine is not started.

Example 2 - Damaged rectifier or vortex generation column

Wave Pattern Characteristics
- Unstable wave pattern with non-uniform frequency.
- However when an ignition leak occurs during acceleration the wave pattern will be distorted temporarily even if the volume air flow sensor is normal.

HARNESS TESTING

Air Flow Sensor:

SCAN TOOL TESTING