5033959 JOHNSON COVER Assy, ENGINE

Illustration 1 g00676880
Schematic for the lamp circuit
Illustration 2 g01150930
Pin locations on ECM connector
(P1-28) Check engine lamp Test Step 1. Inspect Electrical Connectors and Wiring
Thoroughly inspect ECM vehicle harness connector J1/P1, the firewall bulkhead connector, and the check engine lamp (terminal 28). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the check engine lamp. Refer to Illustration 2.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for abrasion and pinch points from the battery 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 or of pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - 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 for Normal Operation of the Lamp
Monitor the check engine lamp.
Turn the ignition key switch to the ON position. The lamp should illuminate for five seconds. Then, the lamp should turn off.
The lamp will continue flashing if there is an active diagnostic code. If there is an active diagnostic code, connect Caterpillar Electronic Technician (ET) in order to read the active diagnostic code. Troubleshoot the problem. Expected Result:The check engine lamp turns on and the check engine lamp turns off per the above description.Results:
Yes - The check engine lamp appears to operate correctly at this time.STOP
No - Proceed to Test Step 3.Test Step 3. Test the Lamp Circuit
Illustration 3 g01150934
Pin locations on ECM connector
(P1-28) Check engine lamp
(P1-67) - Battery
(P1-65) - Battery
Turn the ignition key switch to the OFF/RESET position.
Disconnect ECM vehicle harness connector J1/P1.
Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch pin to both ends of the wire.
Insert the jumper into P1-28 (check engine lamp).
Connect the other side of the jumper wire to P1-65 (-Battery).
Turn the ignition key switch to the ON position.
While the lamp is being watched, insert the jumper wire and remove the jumper wire. Refer to Illustration 3.Expected Result:Result 1 The check engine lamp turns on while the jumper is connected to both sockets. Also, the check engine lamp turns off when the jumper is removed from one of the sockets.Result 2 The check engine lamp does not turn on while the jumper is connected to both sockets.Result 3 The lamp will stay on while the ECM vehicle harness connector is disconnected.Results:
Result 1 - The check engine lamp circuit is functioning properly. Proceed to Test Step 4.
Result 2 - The lamp did not turn on. The vehicle's lamp circuit is not functioning properly. The lamp is probably burned out or there is a problem in the wiring from the cab to either the ECM or the +Battery connection. Repair the lamp circuit or send the vehicle to the OEM dealer for repairs.STOP
Result 3 - Repair: Perform the following diagnostic procedure:The circuit between the ECM and the lamp is shorted to chassis ground. Repair the circuit or send the vehicle to the OEM dealer for repairs.STOPTest Step 4. Check the Operation of the ECM Output for the Check Engine Lamp
Illus