C27 and C32 Engines for Caterpillar Built Machines Caterpillar

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

Table 1

Diagnostic Codes
CDL Code	Code Description	Comments
168-2	Electrical System Voltage : Erratic, Intermittent, or Incorrect	The engine is running. The battery voltage falls below 6 VDC and the voltage returns above 9 VDC for three voltage readings in the last seven seconds.
168-3	Electrical System Voltage : Voltage Above Normal	The ECM detects voltage that is above the acceptable value.
168-4	Electrical System Voltage : Voltage Below Normal	The ECM detects voltage that is below the acceptable value.
1834-2	Ignition Key Switch loss of signal	The ECM detects an erratic signal from the keyswitch. The keyswitch is cycled at least three times in the last second.

The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Cat^® Electronic Technician (ET).

Illustration 1	g02060084
Schematic for the electrical power supply circuit

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat ET to the service tool connector. B. Look for active codes that are associated with the system for the event code.	Codes	Result: An active 168-2 or 1834-2 code is present. Proceed to Test Step 2. Result: An active 168-3 is present. Proceed to Test Step 3. Results: An active 168-4 is present. Proceed to Test Step 4.
2. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the connectors. C. Perform a 45 N (10 lb) pull test on the connector wires. D. Check the harness for abrasions and pinch points.	Connectors and Wiring	Result: The connectors and wiring appear to be OK. Proceed to Test Step 3. Result: There is a problem with the connectors and/or wiring. Repair: Repair or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. If the problem is not resolved, proceed to Test Step 3.
3. Check the Charging Circuit	Charging Circuit	Result: The battery voltage is high. Repair: There is a problem with the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting". If the problem is not resolved, proceed to Test Step 4.
4. Check the Battery A. Turn the keyswitch to the ON position. Do not start the engine. a. Check the brightness of the lights. B. Turn the keyswitch to the ON position. Start the engine. a. Check the brightness of the lights.	Battery	Result: The lights are dim when the engine is not running. The lights are brighter when the engine is running. Repair: There is a problem with the battery. Proceed to Test Step 5. Result: The lights are dim when the engine is not running. The lights are still dim when the engine is running. Repair: There is a problem with the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting". If the problem is not resolved, proceed to Test Step 5.
5. Check the Battery Charge A. Measure the no-load battery voltage at the battery posts. B. Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8 Volt and 12 Volt Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure".	Battery Charge	Result: The batteries pass the load test. The measured voltage is between 11.0 VDC and 13.5 VDC for a 12 V system and between 22.0 VDC and 27.0 VDC for a 24 V system. Repair: Check the wiring between the batteries and the ECM. Check the connectors between the batteries and the ECM for moisture and/or corrosion. Repair the wiring and/or the connectors. Verify that the repair eliminates the problem. 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. 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).