5030542 JOHNSON O-RING

Table 1
Diagnostic Codes Table    
Description    Conditions which Generate this Code    System Response    
168-0 Electrical System Voltage high - most severe (3)     The Electronic Control Module (ECM) detects excessive voltage for 0.5 seconds.     The code is logged.
The warning lamp will illuminate, if equipped.    
168-1 Electrical System Voltage low - most severe (3)     The ECM detects low voltage for 0.5 seconds.     The code is logged.
The warning lamp will illuminate, if equipped.    
168-2 Electrical System Voltage erratic, intermittent, or incorrect     The ECM detects voltage that drops below 6 VDC, then rises above 9 VDC, three times in 7 seconds.
The engine is running.     The engine may be shut down.
The check engine lamp and the warning lamp will illuminate, if equipped.    
1834-2 Ignition Key Switch loss of signal     The ECM detects an erratic signal from the keyswitch because the keyswitch was cycled at least three times in the last second     The code is logged.
The warning lamp will illuminate, if equipped.
The engine will be shut down.    Note: Diagnostic code 1834-2 can be generated by rapidly cycling the keyswitch. If diagnostic code 1834-2 is logged but not active, this condition may be the cause.Use this test if there are intermittent engine shutdowns or if a difficulty in starting is not accompanied by loss of electrical accessories. Engine shutdowns that are accompanied by a loss of other electrical accessories indicate a problem in the keyswitch. This situation does not indicate a problem in the wiring at the engine ECM. Verify that there are no problems with the starting system or the charging system before you use this test.Unswitched battery voltage is supplied through P1: 7, 8, 15, 16. The negative battery is supplied through P1: 1, 2, 3, 9, 10. The ECM receives the input from the keyswitch at P1:40 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.An intermittent power supply to the ECM can occur on either the positive side or on the negative side of the battery circuit. The connections for the unswitched +Battery may be routed through a dedicated protection device (circuit breaker).Some applications may be equipped with an engine protection shutdown system or an idle timer shutdown system that interrupts electrical power to the keyswitch. The engine protection shutdown system can be an aftermarket device and the idle timer shutdown system can be external to the ECM. Some of these systems will not supply power to the ECM until one of the following conditions is met:
The engine is cranked.
The engine oil pressure achieves acceptable limits.
An override button is pressed.Keep in mind that these devices may be the cause of intermittent power to the ECM. These devices may also shut down the engine.The engine ECM requires electrical power in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g01346566
Schematic for the electrical power supply circuit
Illustration 2 g01325674
A typical view of the P1 connector (harness side) pin locations. (1) − Battery (2) − Battery (3) − Battery (7) + Battery (8) + Battery (9) − Battery (10) − Battery (15) + Battery (16) + Battery (40) Ignition key switchTest Step 1. Inspect Electrical Connectors and Wiring
Remove the electrical power from the ECM.
Thoroughly inspect connector P1, the battery connections, and the connections to the keyswitch. Refer to service Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the electrical power supply.
Check the allen head screw on each ECM connector for the proper torque. Refer to service Troubleshooting, "Electrical Connectors - Inspect".
Check the harness for abrasion and for pinch points from the battery to the ECM, and from the keyswitch to the ECM.Expected Result:All connectors, pins, and sockets are correctly coupled and/or inserted and the harness is free of corrosion, of abrasion and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a fault with the connectors and/or the harness.Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are correctly coupled.If applicable, use Cat ET to perform the "Wiggle Test" on the wires that are associated with the electrical power supply.Use Cat ET in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOPTest Step 2. Check the Battery Voltage at the ECM Connector
Disconnect P1 from the ECM connector.
Restore the electrical power to the ECM.
Measure the voltage between P1-7 (Unswitched +Battery) and P1-1 (-Battery).
Measure the voltage between P1-8 (Unswitched +Battery) and P1-2 (-Battery).
Measure the voltage between P1-15 (Unswitched +Battery) and P1-9 (-Battery).
Measure the voltage between P1-16 (Unswitched +Battery) and P1-10 (-Battery).
Measure the voltage between P1-40 (keyswitch) and P1-3 (-Battery).
Remove the electrical power from the ECM.Expected Result:The measured voltage is a constant 22 VDC to 27 VDC with no suspected intermittent faults at this time.Results:
OK - The ECM is receiving the correct voltage. Repair: If an intermittent condition is suspected, refer to service Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - The voltage for the keyswitch is out of the acceptable range. Proceed to Test Step 4.
Not OK - The unswitched power is out of the acceptable range. Proceed to Test Step 3.Test Step 3. Check the Batteries
Measure no-load battery voltage at the battery terminals.
Load-test the batteries. Use a suitable battery load tester.Expected Result:The batteries pass the load test. The measured voltage is the minimum specification.Results:
OK - The batteries pass the load test. Repair: The batteries are OK. 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 connection at the engine ground stud is clean