Electronic Control System Signature, ISX and QSX15 Engines – 019-045   Fan Control Circuit

The Signature system can control the fan clutch activation. The ECM energizes the fan clutch or air valve solenoid.

Refer to vehicle manufacturer’s publications for more information on troubleshooting and repair of the fan clutch wiring.

The fan clutch circuit resides in the actuator harness. The circuit extends from pins 5 and 42 in the actuator harness to pins 12 and 13 in the 31-pin Deutsch connector of the sensor harness. From the 31-pin Deutsch connector, the circuit passes through the OEM wiring to the fan clutch.

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.

Disconnect the actuator harness connector from the ECM. Disconnect the OEM wiring at the fan clutch solenoid.

Insert a test lead into pin 5 of the actuator harness connector and connect it to the multimeter probe.

Touch the other multimeter probe to the connector terminal of the fan clutch solenoid. Make sure the fan clutch solenoid is disconnected.

Measure the resistance.

The multimeter

must show a closed circuit (10 ohms or less). If the circuit is closed, it

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

not closed, there is a connection problem or an open circuit in the wiring harness.

Remove the lead from pin 5 and insert it into pin 42 of the actuator harness connector. Touch the other multimeter probe to the connector terminal of the other fan clutch solenoid. Make sure the fan clutch solenoid is disconnected.

Measure the resistance.

The multimeter

must show a closed circuit (10 ohms or less). If the circuit is closed, it

must still be checked for a short circuit to ground and a short circuit from pin to pin.

If the circuit is

not closed, there is a connection problem or an open circuit in the wiring harness.

Check the harness connections at the 31-pin Deutsch connector. If the connections are good, isolate the open circuit to the OEM wiring to the fan clutch solenoid or the actuator harness as described in the following steps.

Check the OEM wiring to the fan clutch solenoid for an open circuit. Disconnect the 31-pin Deutsch connector.

Insert the multimeter probe with attached lead to pin 12 of the 31-pin connector.

Touch the other multimeter probe to the fan clutch solenoid connector terminal. Measure the resistance.

The multimeter

must show a closed circuit (10 ohms or less). If the circuit is

not closed, there is an open circuit in the OEM wiring to the fan clutch solenoid. Repair or replace the OEM harness according to the OEM procedures.

Remove the lead from pin 12 of the 31-pin connector and insert it into pin 13 of the 31-pin connector.

Touch the other multimeter probe to the fan clutch solenoid connector terminal. Measure the resistance.

The multimeter

must show a closed circuit (10 ohms or less). If the circuit is

not closed, there is an open circuit in the OEM wiring to the fan clutch solenoid.

Repair or replace the OEM harness according to the OEM procedures.

Connect all components after completing the repairs.

Check for a short circuit between pin 5 and all of the other pins in the actuator harness. Make sure the fan clutch solenoid is disconnected. Make sure the battery voltage supply is disconnected.

Insert a test lead into pin 5 of the actuator harness connector. Insert the other test lead into all of the other pins of the actuator harness connector, one at a time.

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 pin 5 and

any pins that measured a closed circuit.

Repair or replace the actuator wiring harness.

Refer to Procedure

019-250
or

019-043.

Check for a short circuit between pin 42 and all of the other pins in the actuator harness connector. Make sure the fan clutch solenoid is disconnected. Make sure the battery voltage supply is disconnected.

Insert a test lead into pin 42 of the actuator harness connector. Connect it to the multimeter probe. Insert the other probe into all of the other pins of the actuator harness connector.

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 pin 42 and any pins which measured a closed circuit.

Repair or replace the actuator wiring harness. Refer to Procedure

019-250or

019-043.

Connect all components after the repair is complete.