CM870 and ISX Engines – 019-049   Fuel Shutoff Valve Circuit

The fuel shutoff valve is located on the fuel system housing. The valve is controlled by the ECM.

NOTE: Only one wire from the ECM will be attached to the valve post. The ECM is not capable of supplying power for other auxiliary components. If an external voltage source is attached, a fault code will be induced.

Turning the vehicle keyswitch on signals the ECM to open the fuel shutoff valve. The valve closes when the ECM senses the vehicle keyswitch is turned off or when the ECM senses an engine overspeed.

The fuel shutoff valve circuit consists of the fuel shutoff valve and fuel shutoff valve signal.

Disconnect the engine harness from the ECM. Check for damaged pins.

Disconnect the fuel shutoff valve signal wire from the valve terminal post.

CAUTION  Do not use probes or leads other than Part No. 3822758. The connector will be damaged. The leads must fit tightly in the connector without expanding the pins of the connector.

Insert a test lead into the fuel shutoff valve signal pin of the engine harness connector. Connect it to the multimeter probe.

Touch the other multimeter probe to the fuel shutoff valve signal wire. Measure the resistance. The multimeter must show a closed circuit (10 ohms or less). If the circuit is not closed, repair or replace the engine harness.

Refer to Procedure 019-250 or 019-043.

If the circuit is closed, it must still be checked for a short circuit to ground and a short circuit from pin to pin.

Insert a test lead into the fuel shutoff valve signal pin of the engine harness connector and connect it to the multimeter probe. Touch the other multimeter probe to engine block ground. The ring terminal at the solenoid must be disconnected and can not touch anything that is grounded. Measure the resistance. The multimeter must show an open circuit (more than 100k ohms). If the circuit is not open, there is a short circuit to ground in the wire connected to the fuel shutoff valve signal pin. Repair or replace the engine harness. Refer to Procedure 019-250 or 019-043.

Check for a short circuit from the fuel shutoff valve signal pin to all of the other pins in the engine harness connector. Insert a test lead into the fuel shutoff valve signal pin of the engine harness connector and connect the lead to the multimeter probe. Insert the other test lead into all other pins of the engine harness connector, one at a time.

The ring terminal at the solenoid must be disconnected and can not touch anything that is grounded. The battery voltage supply must be disconnected.

Measure the resistance.

The multimeter must show an open circuit (more than 100k ohms). If the circuit is not open, there is a short circuit between the fuel shutoff valve signal pin and any pin that did not measure an open circuit.

Repair or replace the engine harness. Refer to Procedure 019-250 or 019-043.