How to test the Air Flow Meter on a GT4 ST165

Test the AFM

* Only applicable to the 165 and 185 - the 205 is not fitted with an AFM *

Why do I want to test my AFM?

If your car won't start or you have a problem, or you have error codes that you are using to track down the fault, then you can eliminate or identify the AFM as your problem using this test procedure.

How do I test it?

You can leave it in the car. To test it you can either:

Unplug the connector to it - it just pulls off. Make sure you pull it via the plastic housing and not the wires - you don't want to introduce faults!
Carry out the test at the ECU

As a functional test you can push the flap at the intake to the unit and ensure that the flap swings smoothly.

What's next?

Take your multimeter, set it to "Resistance Ω" and test between the following connections...


165 AFM connector	185 AFM connector	At the ECU. 165 pin out article here

Between terminals...	165 Resistance Ω	185 Resistance Ω	Temperature ^oC
VS - E2	200 - 600	200 - 600	n/a
VC - E2	200 - 400	200 - 400	n/a
THA - E2	10 - 20k 4 - 7k 2 - 3k 0.9 - 1.3k 0.4 - 0.7k	10 - 20k 4 - 7k 2 - 3k 0.9 - 1.3k 0.4 - 0.7k	-20 0 20 40 60
FC - E1	Infinity	n/a	n/a

What's the temperature column all about?

In the AFM inlet is a small white plastic thing, this is the air intake temperature sensor. The resistance value of this sensor changes as the air intake temperature changes. Simply take a reading and compare to the chart, guessing at what the ambient temperature might be.

Anything else?

Note that FC is connected to earth, E1, in order to turn on the fuel pump on the 165, the 185 does not have this arrangement.

The 185 CS/RC uses a different AFM to both the 165 and 185. This is physically larger, but I would assume that the wiring would remain the same.