019-033   Engine Brake Enable Circuit

The CELECT™ system controls when the engine brakes can be activated. The CELECT™ system does

not control the engine brakes. The system uses a relay to enable the engine brakes to be on when certain conditions are present. The activation and power of the engine brake solenoids are supplied through the vehicle OEM wiring and switches.

The engine brake enable circuit is in the actuator wiring harness and the sensor wiring harness. The circuit goes from pin 18 in the actuator wiring harness to pin C in the three-way connector of the sensor wiring harness. The circuit then goes to pin F in the 9-pin OEM connector. From the 9-pin OEM connector, the circuit goes through the OEM wiring to the engine brake enable relay.

Disconnect the actuator connector from the ECM.

Remove the engine brake enable relay. Refer to the vehicle wiring diagram for the location of the relay. The location will vary with vehicle make and model.

CAUTION  To reduce the possibility of connector damage, do not use probes or leads other than Part Number 3822758. The leads must fit tightly in the connector without expanding the pins in the connector.

Insert the pin of one lead into pin 18 of the actuator connector. Connect the alligator clip to one multimeter probe.

Touch the other multimeter probe to the connector terminal at the engine brake relay socket. 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 to ground and a short from pin to pin. If the circuit is

not closed, there is either a connection problem or there is an open circuit in the wiring harness. Repair according to the OEM instructions.

Check the harness connections at the three-way connector on the sensor harness and at the 9-pin OEM connector. If the connections are good, isolate the open circuit from the OEM wiring to the engine brake enable relay, the sensor wiring harness, or the actuator wiring harness as follows.

Check the OEM wiring to the relay for an open circuit. Disconnect the 9-pin OEM connector. Touch the multimeter probe to pin F at the 9-pin OEM connector. Touch the other multimeter probe to the connector terminal at the engine brake relay. 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 engine brake relay. Repair according to the OEM instructions.

Connect the 9-pin OEM connector. Check the sensor harness for an open circuit. Disconnect the three-way connector from the sensor harness. This connector is near the 9-pin OEM connector.

Touch the multimeter probe to pin C at the three-way connector, sensor harness side. Touch the other multimeter probe to pin F of the 9-pin OEM connector. 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 wire between pin C of the three-way connector and pin F of the 9-pin OEM connector of the sensor harness. Repair or replace the sensor harness. Refer to Procedure 019-043.

Check the actuator harness for an open circuit. Insert the pin of the electrical lead into pin 18 of the actuator connector. Connect the alligator clip to the multimeter probe. Touch the other multimeter probe to pin C at the three-way connector, the actuator wiring harness side.

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 actuator wiring harness. Repair or replace the actuator harness. Refer to Procedure 019-043.

Connect the three-way connector.

CAUTION  To reduce the possibility of connector damage, do not use probes or leads other than Part Number 3822758. The leads must fit tightly in the connector without expanding the pins in the connector.

Check for a short circuit to chassis ground in the engine brake enable wire connected to pin 18. Make sure the engine brake enable relay is removed.

Insert the pin of one lead into pin 18 of the actuator connector. Connect the alligator clip to the multimeter probe.

Touch the other multimeter probe to the engine block. Measure the resistance. The multimeter

must show an open circuit (100k ohms or more). If the circuit is

not open, there is a short to ground in the wire connected to pin 18.

Isolate the short circuit to ground from the OEM wiring to the engine brake enable relay, the sensor harness, or the actuator wiring harness.

Check the OEM wiring to the relay for a short circuit to ground. Disconnect the 9-pin OEM connector. Touch the multimeter probe to pin F of the 9-pin OEM connector, OEM wiring side. Touch the other multimeter probe to chassis ground. Measure the resistance. The multimeter

must show an open circuit (more than 100k ohms). If the circuit is

not open, there is a short to ground in the OEM wiring to the relay. Repair according to the OEM instructions.

Connect the 9-pin OEM connector. Check the sensor harness for a short circuit to ground. Disconnect the 3-way connector from the sensor harness. This connector is near the 9-pin OEM connector.

Touch the multimeter probe to pin C of the three-way connector, sensor harness side. Touch the other multimeter probe to the engine block. 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 between pin C of the three-way connector and pin F of the 9-pin OEM connector sensor harness. Repair or replace the sensor harness. Refer to Procedure 019-043.

Connect the three-way connector. Check the actuator wiring harness for a short circuit to ground. Insert the multimeter lead into pin 18 of the actuator connector. Connect the alligator clip to the multimeter probe. Touch the other multimeter probe to the engine block. 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. Repair the wire connected to pin 18 or replace the actuator wiring harness. Refer to Procedure 019-043.

Check for a short circuit between pin 18 and all other pins. Make sure the engine brake enable relay is removed and the battery voltage supply is disconnected. Insert the pin of the lead into pin 18 of the actuator connector. Connect the alligator clip to the multimeter probe. Insert the pin of the other electrical lead into all of the other pins of the actuator 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 18 and any pin that measured a closed circuit. If the short circuit is measured between any pin except pin 7 or pin 26, the short circuit will be in the actuator wiring harness. Repair or replace the actuator wiring harness. Refer to Procedure

019-043.

If there is a short circuit between pin 18 and pin 7 (fan clutch circuit)
or 26 (keyswitch circuit), the short circuit is in one of the following circuits:

1. OEM wiring to the engine brake enable relay
2. Sensor wiring harness between pin C of the three-way connector and pin F of the 9-pin connector
3. Actuator wiring harness between pin C of the three-way connector and pin 18 of the actuator harness connector.

Check the OEM wiring to the relay for a short from pin to pin. Disconnect the 9-pin OEM connector. Touch the multimeter probe to pin F of the 9-pin OEM connector, OEM wiring side. Touch the other multimeter lead to pin D, then pin E. Measure the resistance. The multimeter

must show an open circuit (more than 100k ohms) for both checks. If the circuit is

not open, there is a short circuit to any wire that measured a closed circuit. Repair or replace the OEM wiring to the relay according to the OEM instructions.

Connect the 9-pin OEM connector. Check the sensor harness for a short circuit from pin to pin. Disconnect the three-way connector from the sensor harness. This connector is near the 9-pin OEM connector.

Touch the multimeter probe to pin C of the three-way sensor harness connector. Touch the other multimeter lead to pin A (vehicle keyswitch circuit);
then touch pin B (fan clutch circuit).

Measure the resistance. The multimeter

must show an open circuit (more than 100k ohms) for both checks. If the circuit is

not open, there is a short circuit to any wire that measured a closed circuit. Repair or replace the sensor harness. Refer to Procedure

019-043.

Connect the three-way connector. Check the actuator wiring harness for a short circuit from pin to pin. Insert the lead into pin 18 (engine brake enable circuit) of the actuator connector. Insert the other lead into pin 7 (fan clutch circuit), then pin 26 (vehicle keyswitch circuit).

Measure the resistance. The multimeter

must show an open circuit (more than 100k ohms) for both checks. If the circuit is

not open, there is a short circuit to any wire that measured a closed circuit. Repair or replace the actuator wiring harness. Refer to Procedure

019-043.

Check for a short circuit from the engine brake circuit to a 12-VDC source. Connect the battery voltage supply if it has been disconnected. Disconnect the 9-pin OEM connector. Touch the multimeter probe to pin F at the connector, OEM wiring side. Touch the other multimeter probe to the engine block.

NOTE: An external voltage source is

any wire in the OEM wiring that carries voltage.

Turn the multimeter dial to measure voltage. Turn the vehicle keyswitch ON. Measure the voltage. The voltage

must be 1.5 VDC or less. If the voltage is

not correct, there is a short circuit between the OEM wiring to the engine brake enable relay and an external voltage source. Remove the voltage source.