Engine Speed Sensor: Testing and Inspection

Diagnostic Procedures


Engine Speed Sensor, Checking

Function

The Engine Speed (RPM) Sensor (G28) detects engine speed and reference marks. The engine will not start if there is no engine speed signal. If the engine is running and the engine speed signal stops, the engine will stop immediately.

Special tools, testers and auxiliary items required

• Hand multimeter (V.A.G 1526) or Multimeter (V.A.G 1715)

• Test adapter kit (V.A.G 1594)

• Wiring diagram

Test conditions

• Battery voltage (both batteries) must be at least 11.5 Volts.

• All electrical consumers such as, lights and rear window defroster must be switched off.

• For vehicles with automatic transmission, selector lever must be in " P".

• Parking brake must be engaged.

• The Ground (GND) connections between engine and body must be OK.

• Ignition switched off.

• Fuses in right instrument panel fuse holder must be OK:

Right instrument panel fuse holder





Test Sequence

- Disconnect 3-pin connector - arrow - to Engine Speed (RPM) Sensor (G28).


Checking Voltage Supply

- Connect multimeter between terminal 1 (B+) and 3 (Ground (GND)) (connector to ECM) for voltage measurement.





- Switch ignition on. Specification: at least 4.5 V

- Switch ignition off.

If no voltage is present:

- Check wires to control module according to wiring diagram.

Check Wires to Control Module

- Connect test box to Engine Control Module (ECM) (J623) wiring harness on connecting test box for wiring test, refer to Repair Manual,

- Check wires between test box and 3-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram. Terminal 1+Socket 98, Terminal 2+Socket 82, Terminal 3+Socket 90, wire resistance: max. 1.5 ohms





- Check wires for short circuit to each other. Specification: infinite ohms

- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.

If no malfunction is found in the wires and there was voltage between terminals 1 + 3:

- Remove sensor and check sensor wheel for secure fit, damage and run-out.

• There is a larger gap on sensor wheel. This gap is a reference mark and not damage.

If no malfunction can be detected at sensor wheel:

- Replace Engine Speed (RPM) Sensor (G28).

- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.

If no malfunction is found in the wires and there was no voltage between terminals 1 + 3:

If no malfunction is detected in the wiring, replace the engine control module.