C175 Petroleum Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engines Electronic Control Module (ECM). Use this procedure if any of the codes in Table 1 are active or easily repeated.

Table 1

J1939 Code and Description	CDL Code and Description	Comments
168-3 Electrical System Voltage : Voltage Above Normal	168-3 Battery Potential / Power Input #1 : Voltage Above Normal	The ECM detects voltage that is above the acceptable value.
168-4 Electrical System Voltage : Voltage Below Normal	168-4 Battery Potential / Power Input #1 : Voltage Below Normal	The ECM detects voltage that is above the acceptable value.

Probable Causes

• Codes

• Circuit

• Battery

Recommended Actions

Table 2

Troubleshooting Test Steps	Value	Results
1. Check for Codes A. Establish communication between the Cat® Electronic Technician (ET) and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Start the engine. Run the engine until the engine is at normal operating temperature. C. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 30 seconds so that any codes may become active.	Codes	Result: A -3 or -11 diagnostic code is active. Proceed to Test Step 2. Result: A -4 diagnostic code is active. Proceed to Test Step 3
2. Check the Charging Circuit A. Check the charging circuit. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting".	Charging circuit	Result: The charging system is OK. Proceed to Test Step 3. Result: The charging system is not OK. Repair: There is a problem with the charging system. Make the necessary repairs. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting". If the problem is not resolved, proceed to Test Step 3.
3. Load Test the Battery A. Load test the battery. Refer to Systems Operation and Testing and Adjusting, "Battery - Test"	Load test	Result: The battery voltage is low or the battery did not pass the load test. Repair: Recharge or replace the faulty batteries. Verify that the repair eliminates the problem. Result: The batteries pass the load test. The measured voltage is between 11.5 VDC and 13.5 VDC for a 12 v system. The measured voltage is between 23.0 VDC and 27.0 VDC for a 24 v system. Repair: Check the wiring between the batteries and the ECM / NOx sensor. Refer to the application-specific wiring schematic for pin locations. Check the connectors between the batteries and the ECM / NOx sensor for moisture and/or corrosion. Repair or replace the wiring and/or the connectors. Verify that the repair eliminates 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).