PLATE 9R8760 - Caterpillar

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 does not indicate a problem with the wiring at the Electronic Control Module (ECM). Verify that there are no problems with the starting system or the charging system before you use this test.Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the ECM or if any one of the diagnostic codes in Table 1 is active or easily repeated.
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 3 seconds.
The engine has been running for at least 30 seconds.     The code is logged.    
168-1 Electrical System Voltage low - most severe (3)     The battery supply voltage is less than 9 VDC for 0.5 seconds.
The engine's ECM has been powered for 3 seconds.
The engine is running for at least 3 seconds.    
168-2 Electrical System Voltage erratic, intermittent, or incorrect     The battery voltage falls below 6 VDC and the voltage returns above 9 VDC for three voltage readings in the last 7 seconds.
The engine is running.    Unswitched battery voltage is supplied to the ECM at P1-48, P1-52, and P1-53. The negative battery is supplied to the ECM at P1-61, 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 g01368963
Schematic for the electrical power supply circuit
Illustration 2 g01364991
Location of the connectors that are for the electrical power supply circuit (typical left side engine view) (1) Engine interface connector (2) J1/P1 ECM connectors
Illustration 3 g01341802
Terminal locations at the P1 ECM connectors for the electrical power supply circuit (P1-48) +Battery (P1-52) +Battery (P1-53) +Battery (P1-61) −Battery (P1-63) −Battery (P1-65) −Battery (P1-70) Keyswitch
Table 2
Troubleshooting Test Steps     Values     Results    
1. Inspect the Electrical Connectors and the Wiring
A. Remove electrical power from the engine ECM.
B. Thoroughly inspect connectors (1) and (2). Inspect all of the connectors that are in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a
45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
D. Check the allen head screw for each of the ECM connectors for