3406E, C-10, C-12, C-15, C-16 and C-18 On-highway Engines Caterpillar

Use this procedure under the following situation:

There is an active diagnostic code or a diagnostic code can easily be activated. This procedure covers open circuit diagnostic codes and short circuit diagnostic codes that are associated with the following sensors:

• Coolant Temperature Sensor

• Intake Manifold Air Temperature Sensor

• Fuel Temperature Sensor

• Optional Ambient Air Temperature Sensor

The following background information is related to this procedure:

The troubleshooting procedures for the diagnostic codes of each temperature sensor are identical. The temperature sensors are sensors that have two terminals. Terminal 2 is the common wire that is shared between all temperature sensors. The common wire provides a path to ground. Terminal 1 is the signal wire from each temperature sensor. The signal wire connects to a unique terminal on the J2/P2 ECM connector for each temperature sensor.

Illustration 1	g00994858
C-10 and C-12 Temperature sensors

Illustration 2	g00995917
3406E Temperature sensors

Illustration 3	g00994860
C-15, C-16 and C-18 Temperature sensors

Illustration 4	g00970545
Schematic for engine temperature sensors

Illustration 5	g00970546
P1 and P2 ECM connectors

Test Step 1. Inspect Electrical Connectors and Wiring

1. Thoroughly inspect the J2/P2 ECM connector and the suspect sensor connector. Refer to Troubleshooting, "Electrical Connections - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the sensor connector and the ECM connector that are associated with the active diagnostic code.

3. Verify that the latch tab of the connector is properly latched and that the latch tab of the connector has returned to the Fully Latching position.

4. Check the ECM Connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

5. Check the harness and wiring for abrasion and pinch points from the sensor to the ECM.

Expected Result:

All connectors, pins, and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion, or pinch points.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Determine the Condition that is Present

1. Connect the electronic service tool to the data link connector.

2. Turn the keyswitch to the ON position. Wait at least 30 seconds for activation of the diagnostic codes.

3. Check for active diagnostic codes on the electronic service tool.

4. Determine if the problem is related to a "voltage high" diagnostic code (open circuit) or a "voltage low" diagnostic code (short circuit).

Expected Result:

A "voltage high" diagnostic code (open circuit) or a "voltage low" diagnostic code (short circuit) is active.

Results:

• Voltage High (Open) - A "voltage high" diagnostic code (open circuit) is active at this time. Proceed to Test Step 5.

• Voltage Low (Short) - A "voltage low" diagnostic code (short circuit) is active at this time. Proceed to Test Step 3.

Test Step 3. Disconnect the Suspect Sensor

1. Turn the keyswitch to the OFF position.

2. Disconnect the sensor with the "voltage low" diagnostic code (short circuit).

3. Turn the keyswitch to the ON position. Wait at least 30 seconds for activation of the diagnostic codes.

4. Check for an active "voltage high" diagnostic code (open circuit) on the electronic service tool.

Expected Result:

A "voltage high" diagnostic code (open circuit) for the suspect sensor is now active.

Results:

• OK - A "voltage high" diagnostic code (open circuit) for the suspect sensor is now active.

  Repair: Temporarily connect a new sensor.If the new sensor fixes the problem, reconnect the suspect sensor.If the problem returns, permanently replace the sensor.Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a short circuit between the sensor harness connector and the ECM.

  Repair: Leave the sensor disconnected.

  Proceed to Test Step 4.

Test Step 4. Disconnect the ECM Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the J2/P2 ECM connector. Thoroughly inspect both halves of the connector for signs of corrosion or moisture.

   Note: If the Ambient Air Temperature Sensor is being tested, a 140-2266 Cable (Seventy-Pin Breakout) is required in order to maintain the battery connections.

3. Turn the keyswitch to the ON position. Wait at least 30 seconds for activation of the code.

4. Check for active diagnostic codes on the electronic service tool.

   Note: When the J2/P2 ECM connector is disconnected, all of the "voltage high" diagnostic codes (open circuit) for the temperature sensors will be active. This is normal.

Expected Result:

"Voltage high" diagnostic codes (open circuit) are active when the J2/P2 ECM connector is disconnected.

Results:

• OK - The ECM is working properly.

  Repair: There is a short circuit in the harness between the connector for the sensor and the ECM connector. Repair the wiring and/or the connector.

  STOP

• Not OK - A "voltage low" diagnostic code (short circuit) is still active for the suspect sensor.

  Repair: Temporarily connect a test ECM.If the test ECM fixes the problem, reconnect the suspect ECM.If the problem returns, permanently replace the suspect ECM.Verify that the repair eliminates the problem.

  STOP

Test Step 5. Create a Short at the Sensor

1. Fabricate a jumper wire 150 mm (6 inch) long.

2. Turn the keyswitch to the ON position.

3. Monitor the active diagnostic code screen.

4. Install the jumper wire between terminal 1 and terminal 2 of the sensor connector.

Expected Result:

A "voltage low" diagnostic code (short circuit) is active when the jumper wire is installed.

Results:

• OK - A "voltage low" diagnostic code (short circuit) is active.

  Repair: Temporarily connect a new sensor.If the new sensor fixes the problem, reconnect the suspect sensor.If the problem returns, permanently replace the suspect sensor.Verify that the repair eliminates the problem.

  STOP

• Not OK - A "voltage high" diagnostic code (open circuit) is still active.

  Repair: Remove the jumper wire.

  Proceed to Test Step 6.

Test Step 6. Create a Short at the ECM

1. Turn the keyswitch to the OFF position.

2. Disconnect the P2 ECM connector.

3. Fabricate a jumper wire 150 mm (6 inch) long.

4. Install the jumper wire between the terminal for the sensor's signal wire and the terminal for the sensor common on the P2 ECM connector.

5. Reconnect the P2 ECM connector.

6. Turn the keyswitch to the ON position.

7. Monitor the active diagnostic code screen.

Expected Result:

A "voltage low" diagnostic code (short circuit) is active when the jumper wire is installed.

Results:

• OK - A "voltage low" diagnostic code (short circuit) is active when the jumper wire is installed.

  Repair: There is an open circuit in the harness between the connector for the sensor and the ECM connector. Repair the wiring and/or the connector.

  STOP

• Not OK - A "voltage high" diagnostic code (open circuit) is still active.

  Repair: Temporarily connect a test ECM.If the test ECM fixes the problem, reconnect the suspect ECM.If the problem returns, permanently replace the suspect ECM.Verify that the repair eliminates the problem.

  STOP