Technical Handbook • Fuel / Intake / Diagnosis
Porsche 944 AFM Testing
Key pinout, voltage targets, and resistance values for testing the Porsche 944 air flow meter (AFM) on the bench or through the DME harness.
The late Porsche 944 AFM operates on a 5-volt supply. For bench testing apply 5V to AFM Pin 3 and ground to Pin 4. Then check the two output signals.
Air-Flow Signal
≈0.25 V closed → ≈4.6 V open
Voltage should increase smoothly as the flap moves, with no dropouts or dead spots.
Air Temperature Signal
≈3.6kΩ → 1.4kΩ (50-86°F)
≈1.3kΩ around 104°F. Resistance decreases as temperature rises.
Healthy AFM behavior: correct start and end values with a smooth voltage progression as the air flap moves.
The AFM pin numbers are molded into the connector port on the meter itself. When looking directly at the male connector blades on the AFM, the pins run:
4 → 3 → 2 → 1 (left to right)
| Pin | Function | Expected Value |
|---|---|---|
| 1 | Air Temperature | ≈3.6k-1.4kΩ depending on temperature |
| 2 | Air Flow Signal | ≈0.25-4.6V across flap travel |
| 3 | 5V Supply | Bench test supply |
| 4 | Ground | Signal reference |
| DME Pin | Equivalent | Function |
|---|---|---|
| 6 | AFM 4 | Ground |
| 9 | AFM 3 | 5V Supply |
| 7 | AFM 2 | Air Flow Signal |
| 22 | AFM 1 | Air Temp Signal |
Testing from the DME connector allows you to check both the AFM and the harness at the same time.
- Hesitation or stumble during acceleration
- Mixture or fueling problems
- Unknown component history
- Suspected worn AFM track
- Baseline diagnostic testing