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 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.

Test procedure 

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

Function test 

-- Connect the scan tool.

-- Switch the ignition On.

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

Diagnostic text		Specified value
Engine rotations per minute (RPM)		Idle speed

-- Switch ignition Off.

If the specified value was Not obtained:

Start diagnosis 

-- Disconnect the Engine Speed Sensor -G28- electrical harness connector.

Checking internal resistance 

-- Using a multimeter, check the Engine Speed Sensor -G28- terminals 2 to 3 for resistance.

Specified value: 700 to 1000 Ohm

-- Check Engine Speed Sensor -G28- terminals 1 to 2 and 1 to 3 for short circuits.

Specified value: ∞ (infinity)

If any of the specified values are Not obtained:

-- Replace the Engine Speed Sensor -G28-.

If the specified values were obtained:

Checking wiring 

If the manufacturers test box is being used. Perform the following step.

-- Install the test box.

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

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

-- Using a multimeter, check the Engine Speed Sensor -G28- electrical harness connector terminals to the Engine Control Module (ECM) -J623- electrical harness connector T121 terminals for resistance.

Engine Speed Sensor -G28- electrical harness connector terminals	Engine Control Module (ECM) -J623- electrical connector T121 terminals or test box sockets
1	108
2	90
3	82

Specified value: 1.5 Ω Max.

If the specification was Not obtained:

-- Check the wiring for an open circuit, high resistance, a short circuit to each other, Battery (+) or Ground.

-- Check wiring shield for proper ground.

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

-- If necessary, repair the faulty wiring connection.

If the specification was obtained:

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

If the sensor wheel is OK:

-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Perform a road test to verify repair.

If the DTC does not return:

Generate readiness code. Refer to READINESS CODE .

If the DTC returns, no malfunction is found in the wiring and the voltage supply was OK:

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

-- Assembly is performed in the reverse of the removal.

Final procedures 

After 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 .