Engine Speed Sensor, Checking

Engine Speed Sensor, Checking

• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Engine Speed (RPM) Sensor (G28).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Engine Control Module (ECM) (J623) fuses OK.

• Battery voltage at least 12.5 V.

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

• Vehicles with automatic transmission, shift selector lever into position "P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test Procedure

- Perform a preliminary check to verify the customer's complaint. Refer to => [ Preliminary Check ] Preliminary Check

The Engine Speed (RPM) Sensor (G28) detects RPM 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.

Function test

- Connect the scan tool.

- Switch the ignition on.

- Using the scan tool, check the engine speed:





- End diagnosis and switch ignition off.

If the specified value was not obtained:

Checking internal resistance

- Disconnect the electrical harness connector - arrow - from the Engine Speed (RPM) Sensor (G28).





- Using a multimeter, check the Engine Speed (RPM) Sensor (G28) terminals1 to 2 for resistance.





Specified value: 450 to 1000 ohms.

• Resistance value of the engine speed (RPM) sensor is based on a temperature of 20° C. Resistance increases as temperature increases.

If specified value is not obtained:

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

If specified value is obtained:





- Using a Multimeter , check the electrical harness connector terminals for voltage.





Specified value: Battery voltage.

If specified value is not obtained:

- Check the wiring for short circuit to each other as well as to Battery positive (+) and Ground (GND).

- If necessary, repair the wiring connection.

If no malfunctions are detected in the wiring and if the voltage supply was OK:

Checking wiring connections

If the manufacturers test box is being used, perform the following step.

- Connect the Test Box 105 Pin (VAG1598/42) with Adapter Cable (1598/39-1).

If the manufacturers test box is not being used, perform the following step.





- Remove the Engine Control Module (ECM) (J623). Refer to=> [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

Using a Multimeter, check the Engine Speed (RPM) Sensor (G28) electrical harness connector terminals to the Engine Control Module (ECM) (J623) electrical harness connector terminals for resistance.





Specified value: 1.5 ohms max.

If the specification is not obtained:

- Check the wiring for a short circuit to Battery positive (+) or an open circuit.

- If necessary, repair the wiring connection.

If no malfunctions are detected:

- Replace the Engine Control Module (ECM) (J623). Refer to=> [ Engine Control Module, Replacing ] Engine Control Module, Replacing

Assembly is performed in reverse order of removal, note the following:

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.