PLATE & BOSS GP-COUPLER 4494688 - Caterpillar

The external lamps should go out when the truck is moving. If the external lamps do not go out, the cause is probably that the PMC is not receiving a speed signal. Test Step 1. CHECK THE SPEED SENSOR
Observe the speedometer while accelerating the truck to about 16 km/h (10 mph). Expected Result:The speedometer indicates speed normally.Results:
OK - The speedometer indicates speed normally. The speed sensor is working correctly. Proceed to Test Step 2.
NOT OK - The speedometer does not indicate speed normally.Repair: Check the the speed sensor, the speed distributor, the Transmission ECM, and the associated wiring.STOPTest Step 2. VERIFY THE SPEED SIGNAL
Press the mode switch until mode "-7-" is shown on the display of the POD.
Press the "Test/Set" switch until circuit "A20" (transmission output speed) is shown on the display of the POD.
Accelerate the truck to about 5 to 8 km/h (3 to 5 mph). Expected Result:"A20" changes to "C20" on the display of the POD.Results:
OK - "A20" changes to "C20" on the display of the POD. The PMC is receiving a good speed signal. Repair: Check the lamp circuits for a short to the +battery circuit. Repair the harness or replace the harness. If no fault is found, replace the PMC.STOP
NOT OK - "A20" does not change to "C20". Proceed to Test Step 3.Test Step 3. CHECK THE SPEED DISTRIBUTOR
Turn the key start switch to the OFF position.
Connect a jumper wire between socket 6 and pin 3 of the connector for speed distributor.
Start the truck.
Accelerate the truck to about 5 to 8 km/h (3 to 5 mph). Note: The speedometer will not work when the speed distributor has been bypassed.Expected Result:"A20" changes to "C20" on the display of the POD. Results:
OK - "A20" changes to "C20" on the display of the POD. The speed distributor has failed.Repair: Replace the speed distributor.STOP
NOT OK - "A20" does not change to "C20" on the display of the POD. Proceed to Test Step 4.Test Step 4. CHECK THE HARNESS
Turn the key start switch to the OFF position.
Disconnect the machine harness connector from the PMC.
Measure resistance between socket 6 of the machine harness connector for the PMC and pin 3 of the machine harness connector for the speed distributor. Expected Result:The resistance is less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. The circuit is correct. Proceed to Test Step 5.
NOT OK - The resistance is greater than 5000 ohms. Wire 794-YL(Yellow) is open in the harness.Repair: Repair the harness or replace the harness.STOPTest Step 5. CHECK THE MACHINE HARNESS
Turn the key start switch to the OFF position.
Disconnect the machine harness connector from the PMC.
Measure resistance between the socket 6 of the machine harness connector for the PMC and all other contacts in the connector and frame ground. Results:
OK - All measurements are greater than 5000 ohms. The circuit is correct. Proceed to Test Step 6.
NOT OK - One or more of the measurements are less than 5 ohms.Repair: Wire 794-YL(Yellow) is shorted in the harness.STOPTest Step