C175 Oil&Gas Offshore Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with a sensor. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

Table 1

J1939 Code and Description	CDL Code and Description	Comments
105–3 Engine Intake Manifold #1 Temperature : Voltage Above Normal	172–3 Intake Manifold Air Temperature Sensor : Voltage Above Normal	The code is logged.
105–4 Engine Intake Manifold #1 Temperature : Voltage Below Normal	172–4 Intake Manifold Air Temperature Sensor : Voltage Below Normal	The code is logged.
110-3 Engine Coolant Temperature : Voltage Above Normal	110-3 Engine Coolant Temperature : Voltage Above Normal	The ECM detects that the voltage is not in the acceptable range. The code is logged.
110-4 Engine Coolant Temperature : Voltage Below Normal	110-4 Engine Coolant Temperature : Voltage Below Normal	The ECM detects that the voltage is not in the acceptable range. The code is logged.
171-3 Ambient Air Temperature : Voltage Above Normal	3667-3 Aftertreatment #1 SCR Cabinet Air Temperature Sensor : Voltage Above Normal	The code is logged.
171-4 Ambient Air Temperature : Voltage Below Normal	3667-4 Aftertreatment #1 SCR Cabinet Air Temperature Sensor : Voltage Below Normal	The code is logged.
174-3 Engine Fuel Temperature 1 : Voltage Above Normal	174-3 Fuel Temperature Sensor : Voltage Above Normal	The code is logged.
174-4 Engine Fuel Temperature 1 : Voltage Below Normal	174-4 Fuel Temperature Sensor : Voltage Below Normal	The code is logged.
3468-3 Engine Fuel Temperature 2 : Voltage Above Normal	2323-3 Fuel Rail Temperature Sensor : Voltage Above Normal	The code is logged.
3468-4 Engine Fuel Temperature 2 : Voltage Below Normal	2323-4 Fuel Rail Temperature Sensor : Voltage Below Normal	The code is logged.

Illustration 1	g06322023
Schematic for the primary passive sensors

Illustration 2	g06322034
Schematic for the secondary passive sensors

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat® Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged.	Codes	Result: A -3 code is active. Proceed to Test Step 2. Result: A -4 code is active. Proceed to Test Step 3. Result: For a code that is logged, but not currently active. Proceed to Test Step 4.
2. Create a Short at the Sensor Connector A. Remove electrical power from the engine. B. Disconnect the sensor with the active -3 code. C. Install the jumper wire between the following terminals at the sensor connector: - Terminal 1 (sensor signal) and Terminal 2 (sensor return) D. Connect Cat ET. E. Use Cat ET to monitor the following: - -4 code F. Remove electrical power from the engine.	Create a Short	Result: The -3 code remains active. Repair: There is a short in the wiring harness. Repair or replace the wiring harness. Verify that the repair eliminated the problem. Result: A -4 code became active. Repair: The wiring harness is OK. Replace the sensor. Verify that the repair eliminated the problem.
3. Create an Open at the Sensor Connector A. Remove electrical power from the engine. B. Disconnect the sensor with the active -4 code. C. Connect Cat ET. D. Use Cat ET to monitor the following: - -3 code Note: For a 110-3 code, start the engine and let the engine idle for 7 minutes. The engine must be running for at least 7 minutes in order for the diagnostic to run. E. Remove electrical power from the engine.	Create an Open	Result: The -4 code remains active. Repair: There is a short in the wiring harness. Repair or replace the wiring harness. Verify that the repair eliminated the problem. Result: A -3 code became active. Repair: The wiring harness is OK. Replace the sensor. Verify that the repair eliminated the problem.
4. Perform the Wiggle Test Carefully following this procedure is the best way to identify the root cause of an intermittent problem. A. Connect Cat ET. B. Use CAT ET to perform the following test: - "Wiggle Test" C. Slowly wiggle the wiring and the connectors between the P2 connector and the sensor. Slowly wiggle the wiring and the connectors between the P1 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all the wiring. D. As you wiggle the wiring look for the following problems: - Loose connectors or damaged connectors - Moisture on the connectors or the wiring - Damage that is caused by excessive heat - Damage that is caused by chafing - Improper routing of wiring - Damaged insulation	Test	Result: The wiring failed the Wiggle Test. Repair: There is a problem with the wiring harness. Repair or replace the wiring harness. Verify that the repair eliminated the problem. Result: The wiring passed the Wiggle Test. Repair: The problem may be intermittent. Inspect the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information. The wiring looks OK perform the following procedure. 1. Remove electrical power from the engine. 2. Disconnect the connectors. Carefully inspect the terminals for proper installation. Make sure that each terminal is clean and dry. 3. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems. 4. Connect all connectors. 5. Verify that the repair eliminated the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).