With Generic Scan Tool

Engine Speed (RPM) Sensor -G28-, checking

Function
The Engine Speed (RPM) Sensor -G28- detects engine speed and reference marks. Without an engine speed signal, the engine will not start. If the engine speed signal fails while the engine is running, the engine will stop immediately.

Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 Connector test set
- Wiring diagram

Test sequence





- Disconnect gray 3-pin harness connector (arrow) to the engine speed (RPM) sensor.

NOTE: To reach this harness connector, remove coolant reservoir attachment screws and tilt coolant reservoir to the side. The coolant hoses remain connected.

Vehicles with engine code AHA





- Measure sensor resistance between terminals 1 + 2 at connector to
sensor.
Specified value: 480 to 1000 Ohms

Vehicles with engine code ATQ





- Measure sensor resistance between terminals 2 + 3 at connector to sensor.
Specified value: 730 to 1000 Ohms

Continuation for all vehicles
- Check sensor for short circuit between terminals 1 + 2 as well as 1 + 3.
Specified value: Infinity Ohms

If specified values are not obtained:
- Replace Engine Speed (RPM) Sensor -G28-, item no. 20 .
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no DTC is found on sensor:
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test

Vehicles with engine code AHA





- Check wires between test box and 3-pin connector for open circuits according to wiring diagram.
Terminal 1 + socket 67
Terminal 2 + socket 63
Terminal 3 + socket 56
Wire resistance: max: 1.5 Ohms

Vehicles with engine code ATQ





- Check wires between test box and 3-pin connector for open circuits according to wiring diagram.
Terminal 1 + socket 108
Terminal 2 + socket 90
Terminal 3 + socket 82
Wire resistance: max: 1.5 Ohms

Continuation for all vehicles
- Also check wires for short circuits to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinity Ohms

If no malfunctions are found in wires:
- Remove sensor and check sensor wheel for secure fit, damage, and run-out.

NOTE: There is a larger-sized gap on the sensor wheel. This gap is the reference mark and does not mean that the sensor wheel is damaged.

If nothing seems to be wrong with the sensor wheel:
- Replace Motronic Engine Control Module (ECM) -J220-.