0304644 JOHNSON NUT,Hex switch

Table 1
Diagnostic Codes Table    
Code and Description    Conditions which Generate this Code    System Response    
168-0 Electrical System Voltage high - most severe (3)     The battery supply voltage is greater than 32 VDC for 0.5 seconds.
The engine's ECM has been powered for three seconds.
The engine is not being cranked.     The code is logged.    
168-1 Electrical System Voltage low - most severe (3)     The battery supply voltage is less than 18 VDC for 0.5 seconds.
The engine's ECM has been powered for three seconds.
The engine is not being cranked.    
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.    Unswitched battery voltage is supplied to the ECM at P1-48, P1-52, P1-53, and P1-55. The negative battery is supplied to the ECM at P1-61, P1-63, P1-65, and P1-67. The ECM receives the input from the keyswitch at P1-70 when the keyswitch is in the ON position or in the START position. When the ECM detects battery voltage at this input, the ECM will power up. When battery voltage is removed from this input, the ECM will power down. The ECM continuously receives battery voltage through the fuse F2 and the battery disconnect switch is in the ON position.The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g01394414
Schematic for the electrical power supply circuit
Illustration 2 g01395011
Terminal locations of the connectors for the fuse block assemblyTest Step 1. Inspect the Electrical Connectors and the Wiring
Turn the battery disconnect switch to the OFF position.
Illustration 3 g01141049
J1/P1 ECM connectors (typical left side engine view)
Thoroughly inspect the J1/P1 ECM connectors. Inspect all of the connectors that are in the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 4 g01302249
P1 connections for the electrical power supply circuit (P1-48) +Battery (P1-52) +Battery (P1-53) +Battery (P1-55) +Battery (P1-61) −Battery (P1-63) −Battery (P1-65) −Battery (P1-67) −Battery (P1-70) Keyswitch
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.Results:
OK - The harness and wiring appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the connectors and/or wiring.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.STOPTest Step 2. Check the Battery Voltage at the ECM
Disconnect the J1/P1 ECM connector.
Turn the battery disconnect switch to the ON position.
Turn the keyswitch to the ON position.
Wiggle the wires in the harness while performing the following test steps.
Measure the voltage between P1-48 (Unswitched +Battery) and P1-61 (−Battery).
Measure the voltage between P1-52 (Unswitched +Battery) and P1-63 (−Battery).
Measure the voltage between P1-53 (Unswitched +Battery) and P1-65 (−Battery).
Measure the voltage between P1-55 (Unswitched +Battery) and P1-67 (−Battery).
Measure the voltage between P1-70 (Keyswitch) and P1-63 (−Battery).Expected Result:The measured voltage is between 22 VDC and 27 VDC.Results:
OK - The ECM is receiving the correct voltage.Repair: There may be an intermittent electrical problem in a harness or in a connector. If an intermittent condition is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - Unswitched power out of range - The voltage is not correct for one of the unswitched battery circuits at the ECM. Verify that the −Battery connections to the ECM have continuity to the engine ground. If the connections are OK, Proceed to Test Step 3. If the connections are not OK, repair the connectors or wiring and/or replace the connectors or wiring.
Not OK - Keyswitch voltage out of range - The voltage is not correct for the keyswitch circuit at the ECM. Proceed to Test Step 5.Test Step 3. Check the Batteries
Measure the no-load battery voltage at the battery posts.
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 and 12 Volt Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure".Expected Result:The batteries pass the load test. The measured voltage is the minimum specification for a 24V system.Results:
OK - The batteries pass the load test. The batteries are OK. There is an open circuit or excessive resistance in the wiring or connections between the batteries and the ECM. Proceed to Test Step 4.
Not OK - 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.STOPTest Step 4. Check the Voltage from the Fuse Block Assembly to the ECM
Disconnect the F-C13 connector from the fuse block assembly.
Turn the battery disconnect switch to the ON position.
Measure the voltage between terminal F-C13-G on the fuse block assembly and engine ground.Expected Result:The measured voltage is between 22 VDC and 27 VDC.Results:
OK - The correct voltage is present at the output of the fuse block assembly.Repair: There is a problem in the wiring between the fuse block