0304500 JOHNSON PIN

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 two 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 9 VDC for two 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 momentarily drops below 9 VDC or the voltage drops below 9 VDC for three voltage readings in the last seven seconds.    Unswitched battery voltage is supplied to the ECM at terminals P1-4 and P1-6. The negative battery is supplied to the ECM at terminals P1-5 and P1-11. The ECM receives the input from the keyswitch at terminal P1-23 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 circuit breaker for the engine ECM.The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g01798313
Schematic for the electrical power supplyTest Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the engine ECM.
Illustration 2 g01139425
ECM (1) J1/P1 connectors (2) J2/P2 connectors
Thoroughly inspect ECM connector J1/P1, ECM connector J2/P2, and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect".
Illustration 3 g01394751
P1 terminals that are associated with the electrical power supply circuit (P1-4) Unswitched +Battery (P1-5) −Battery (P1-6) Unswitched +Battery (P-11) −Battery (P1-23) Keyswitch input
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector.
Check the allen head screw on each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasions and for pinch points from the batteries to the ECM.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.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 circuit. Ensure that all of the seals are properly in place and 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.
Restore electrical power to the ECM.
Turn the keyswitch to the ON position.
Measure the voltage between terminal P1-4 (unswitched +Battery) and terminal P1-11 (−Battery).
Measure the voltage between terminal P1-6 (unswitched +Battery) and terminal P1-5 (−Battery).
Measure the voltage between terminal P1-23 (keyswitch) and terminal P1-11 (−Battery).Expected Result:The measured voltage is between 22 VDC and 27 VDC.Results:
OK - The ECM is receiving the correct voltage.Repair: 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 at the ECM. Proceed to Test Step 3.
Not OK - Keyswitch voltage out of range - Proceed to Test Step 4.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 are OK.Repair: There is an open circuit or excessive resistance in the wiring or connections between the batteries and the ECM. Verify that the 15 Amp circuit breaker for the ECM is not tripped. Verify that the connection at the engine ground stud is clean and tight and that the battery disconnect switch is functioning properly. Repair the connectors or wiring and/or replace the connectors or wiring.STOP
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 Keyswitch to the ECM
Remove electrical power from the engine ECM.
Turn the keyswitch to the OFF position.
Remove the wire from the terminal R of the keyswitch.
Restore electrical power to the engine ECM.
Turn the keyswitch to the ON position.
Measure the voltage on terminal B of the keyswitch to engine ground.
Measure the voltage on terminal R of the keyswitch to engine ground.
Turn the keyswitch to the OFF position.Expected Result:Voltage is present on terminal B and terminal R at the keyswitch.Results:
OK - Voltage is present on terminal B and terminal R at the keyswitch.Repair: If voltage is present on terminal R, repair the circuit between the keyswitch and the ECM. Ensure that the main power relay for the machine is receiving the correct control. Check the condition of the fuse that is in the circuit for the keyswitch. Verify that the problem is eliminated.STOP
Not OK - Voltage is not present on terminal B at the keyswitch.Repair: If voltage is not present on terminal B, repair the wire between the +Battery and the keyswitch. Verify that the circuit breaker for the keyswitch is not tripped. Verify that the problem is eliminated.STOP
Not OK - Voltage is not present on terminal R at the keyswitch.Repair: If voltage is present on terminal B of the keyswitch but not present on terminal R, replace the keyswitch. Return all wiring to the original configuration. Verify that the problem is eliminated.STOP