VALVE GP-CONTROL 3736976 - Caterpillar

This procedure covers the following diagnostic codes:
168-00 System Voltage High
168-01 System Voltage Low
168-02 System Voltage intermittent/erraticThis procedure tests whether proper voltage is being supplied to the Electronic Control Module (ECM). Use this procedure to troubleshoot any suspect problems with the electrical power supply.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 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 cause of an intermittent power supply to the ECM can occur on either the positive side or the negative side of the battery circuit. Both sides are routed from the ECM to the battery.The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).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.
Illustration 1 g01141675
Schematic for the electrical power supply circuit
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01143178
Location of the J1/P1 and J2/P2 ECM connectors (typical left side engine view)
(1) J2/P2 ECM connectors
(2) J1/P1 ECM connectors
Thoroughly inspect connectors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01218813
P1 ECM connections
(P1-48) +Battery
(P1-52) +Battery
(P1-53) +Battery
(P1-61) −Battery
(P1-63) −Battery
(P1-65) −Battery
(P1-70) Keyswitch
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the electrical power supply.
Check the torque of the allen head screws for the ECM connectors. Refer to 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 and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The harness and the connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with the harness and/or the connectors.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 completely coupled.STOPTest Step 2. Check the Battery Voltage at the ECM
Disconnect the J1/P1 ECM connectors.
Turn the keyswitch to the ON position.
Measure the voltage between P1-52 (unswitched +Battery) and P1-63 (−Battery).
Measure the voltage between P1-48 (unswitched +Battery) and P1-61 (−Battery).
Measure the voltage between P1-53 (unswitched +Battery) and P1-65 (−Battery).
Measure the voltage between P1-70 (keyswitch) and P1-63 (−Battery). Expected Result:The measured