0437193 JOHNSON ENGINE COVER ASSY., 60

Table 1
Diagnostic Codes Table    
Description    Conditions which Generate this Code    System Response    
168-1 Electrical System Voltage : Low     The battery supply voltage is less than 9 VDC for two seconds.
The engine ECM has been powered for three seconds.
The engine is not being cranked.     The code is logged if the engine is running.    
168-2 Electrical System Voltage : Erratic, Intermittent, or Incorrect     The engine is running. The battery voltage falls below 9 VDC for at least .06 seconds. The voltage returns above 9 VDC.
or
Three voltage readings in the last seven seconds were below 9 VDC.    Unswitched battery voltage is supplied to the ECM at P1-52 and P1-53. The negative battery is supplied to the ECM at P1-63 and P1-65. 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 circuit breaker for the ECM.The ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g01145646
Typical schematicTest Step 1. Inspect Electrical Connectors and Wiring
Check all circuit breakers.
Turn the keyswitch to the OFF position.
Illustration 2 g01234146
Location of ECM connectors
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect the connections for the battery and the connections to the keyswitch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01526167
P1 ECM connector (P1-52) +Battery (P1-53) +Battery (P1-63) −Battery (P1-65) −Battery (P1-70) Keyswitch
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins, and sockets are coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and wiring are 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 coupled.Verify that the repair eliminates the problem.STOPTest Step 2. 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 V and 12 V 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 12V or 24V system.Results:
OK - The batteries are OK. Proceed to Test Step 3.
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 3. Check the Voltage at the ECM
Disconnect the J1/P1 ECM connector.
Measure the voltage between P1-52 (Unswitched Positive Battery) and P1-63 (Negative Battery).
Measure the voltage between P1-53 (Unswitched Positive Battery) and P1-65 (Negative Battery).
Measure the voltage between P1-70 (Keyswitch) and P1-63 (Negative Battery).Expected Result:The voltage is 1 VDC from the voltage at the battery terminals.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 - Keyswitch voltage out of range - Proceed to Test Step 4.
Not OK - The voltage is not 1 VDC from the voltage at the battery terminals. The voltage is not correct at the ECM.Repair: There is an open circuit or excessive resistance in the wiring or connections between the batteries and the ECM. Verify that the circuit breaker for the ECM is not tripped. Verify that the battery disconnect switch is in the ON position. Verify that the connection for the engine ground is clean and tight. Repair the connectors or wiring and/or replace the connectors or wiring.STOPTest Step 4. Check the Voltage from the Keyswitch to the ECM
Turn the keyswitch to the OFF position.
Remove the wire from the terminal R of the keyswitch.
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 wire between the keyswitch and the ECM. 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 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