Engine Speed Sensor, Checking: Notes

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 will not start. If the engine speed signal fails while the engine is running, the engine will stop immediately.

Test procedure 

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

Start diagnosis 

-- Connect the scan tool.

-- Start the engine and allow it to idle.

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

Diagnostic text		Specified value
Engine revolutions per minute (RPM)		Cranking or idle speed

-- Switch ignition OFF.

If the specified value was obtained: 

-- Check the wiring connection for an open circuit or short circuit.

-- Check the wiring connection for damage, corrosion, loose or broken terminals.

-- If necessary, repair the faulty wiring connection.

-- Go to Final procedures

If any of the specified value was not obtained: 

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

-- Switch the ignition on.

-- Using a Multimeter, Check the Engine Speed Sensor -G28- electrical harness connector terminals X to X for voltage.

Specified value: near 5.0 V

-- Switch the ignition off.

Continue test according to the following table: 

Value	Cause	Test
If the specified value was not obtained:	Open or shorted circuit	Checking wiring
If the specified value was obtained:	Check reference signal circuit	Check reference signal