CLAMP 9M0164 - Caterpillar

System Operation Description:This procedure tests whether proper voltage is being supplied to the Engine Control Module (ECM).Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:
168-02 System Voltage intermittent/erraticAlso, use this procedure if you have been directed from Troubleshooting, "Electronic Service Tool Will Not Communicate with ECM" or Troubleshooting, "Engine Cranks but Will Not Start".Unswitched battery voltage is supplied through the customer connector 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 STOP 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 cause of an intermittent power supply to the ECM can occur on either the positive side or on the negative side of the battery circuit. Both sides are routed from the ECM to the battery. The three connections for the unswitched +Battery must be routed through a dedicated protective device (circuit breaker).The engine ECM requires the input for the keyswitch to be powered in order to maintain communications with the electronic service tool.For intermittent problems such as intermittent shutdowns that could be caused by engine wiring, temporarily bypassing the engine wiring may be an effective means of determining the root cause. If the symptoms disappear with the bypass wiring, the engine wiring is the cause of the problem. A means of bypassing engine wiring is explained in this test procedure.
Illustration 1 g01388327
Schematic for electrical power supply circuit
Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01146374
Left side engine view (typical example)
(1) J1/P1 ECM connector
Illustration 3 g01388311
Left side engine view (typical example)
(2) Customer connector
(3) Service tool connector
Thoroughly inspect connectors (1), (2), and (3). Inspect the terminal connections from the battery to the ECM. Also, inspect the connections from the keyswitch to the ECM. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 4 g01172797
Terminal locations at the P1 ECM connector that are associated with the electrical power supply
(P1-40) Run/stop switch
(P1-48) +Battery
(P1-52) +Battery
(P1-53) +Battery
(P1-61) −Battery
(P1-63) −Battery
(P1-65) −Battery
(P1-70) Keyswitch
Illustration 5 g01172799
Terminal locations at the customer connector that are associated with the electrical power supply
(1) +Battery
(5) +Battery
(8) +Battery
(19) Run/stop switch
(30) Keyswitch
Illustration 6 g01388321
Terminal locations at the service tool connector that are associated with the power supply
(A) Keyswitch
(B) −Battery
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 the ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasions and for pinch points from the battery to the ECM. Also, check the harness and wiring for abrasions and for pinch points from the keyswitch to the ECM. Expected Result:All connectors, pins, and sockets are completely coupled