Engine Speed Sensor, Checking

Engine Speed Sensor, Checking

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 volts.

• 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 connections between engine/transmission/chassis OK.

• Ignition switched OFF.

Test procedure

- Observe safety precautions. Refer to => [ Safety Precautions ] Safety Precautions

- Observe Clean Working Conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions

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

Start diagnosis

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 stall.

Function test

- Connect the scan tool.

- Start the engine.

- Using the scan tool, check the engine speed:






- Switch ignition OFF.

If the specified value was Not obtained:

Checking internal resistance

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

- Using a multimeter, check the Engine Speed (RPM) Sensor (G28) resistance by connecting the RED lead to terminal 1 and the BLACK lead to terminal 2.

Specified value: 7.52 Mohms

- Using a multimeter, connect the RED lead to terminal 3 and the BLACK lead to terminal 2.

Specified value: 1.38 Mohms

If any of the specified values are Not obtained:

- Replace the Engine Speed (RPM) Sensor (G28). Refer to the Repair Information.

If the specified values are obtained:

Checking wiring

- Remove the Engine Control Module (ECM) (J623). Refer to the Repair Information.

- Using a multimeter, check the Engine Speed (RPM) Sensor (G28) electrical harness connector terminals to the Engine Control Module (ECM) (J623) electrical harness connector T60 terminals for resistance.










Specified value: 1.5 ohms Max.

If the specification was Not obtained:

- Check the wiring for an open, high resistance or short circuit to voltage or ground.

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Remove the Engine Speed (RPM) Sensor (G28) and check the sensor wheel for proper seating, damage and run out.

If the sensor wheel is OK , no malfunction is detected in the wiring and the voltage supply is OK:

- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.

Final procedures

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

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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