Engine Speed Sensor, Checking

Special tools and workshop equipment 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.

Function 

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

Test procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK 

Start diagnosis 

-- Connect the scan tool.

-- Start the engine.

-- Using the scan tool, check the engine speed at idle:

Diagnostic text on Scan Tool		Specified value
Engine revolutions per minute (RPM)		Idle speed

-- Switch ignition OFF.

If the specified value was obtained:

-- The fault is intermittent. Check for loose connection or spread/damaged terminals at the sensor.

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- terminals 1 to 2 for resistance.

Specified value: 650 to 1100 Ω

If the specified value was Not obtained:

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

If the specified values were 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 an open circuit.

Engine Speed (RPM) Sensor -G28- electrical harness connector terminals:	Engine Control Module (ECM) -J623- electrical connector T60 terminals:
1	51
2	36

Specified value: 1.5 Ω Max.

If the specified value was Not obtained:

-- Check the wiring for an open circuit, high resistance or a short circuit to Battery positive.

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

-- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

-- Remove the Engine Speed (RPM) Sensor -G28- and check the sensor wheel for proper seating, damage and runout. Refer to the Repair information.

If the sensor wheel is OK:

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

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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .