USING A MULTIMETER

Air Flow Meter function test (2004 Vauxhall Astra SRI)

In many cases, it is worth checking the resistance of an existing component before condemning it. Even if an engine management light is not illuminated, you can also identify a component that might be failing but is just about operating within tolerance. The following sequence proves that the air flow meter is in good condition.

Check the condition of your multimeter and that its readings are zeroed. Discharge any residual voltage, as shown, before starting work.

Check the battery. As this one is discharged and measuring only 8.9 volts between its terminals, a higher voltage cannot be expected at the sensor.

The earth connection between the battery and engine is verified as being in good order by a near identical reading being noted.

A low voltage reading can also result from dirty battery terminals. Prior to replacing the battery, observe any necessary disconnection procedure that might damage ECUS.

Wiring insulation should never be compromised for diagnostic testing – resulting in the pictured damage – because it introduces a weak point for corrosion to enter.

Instead, a metal back-probe (you can use a needle in an emergency) can be tucked behind the plastic plug moulding until it touches a metal contact.