0342386 JOHNSON ARM

Illustration 1 g00702019
Schematic for coolant level switch
Illustration 2 g00702199
ECM connector P1
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect the J1/P1 ECM connector, the J800/P800 coolant level switch connector, and any other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM machine harness connector that are associated with the coolant level switch. Refer to Illustration 2.
Check the ECM machine harness connector (allen head screw) for the proper torque of 6.0 N m (55 lb in).
Check the harness and wiring for abrasions and for pinch points from the coolant level switch back to the ECM.Expected Result:All connectors, pins, and sockets should be completely coupled and/or inserted. The harness and wiring should be free of corrosion, abrasion, and 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. Stop.Test Step 2. Check the Engine Coolant Level
Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.
Stop the engine.
After allowing the engine to cool, check the coolant level. Refer to the operating documentation that was supplied with the equipment for the proper procedure.
Check for external coolant leaks.Results:
OK - Proceed to Test Step 3.
Not OK - Add coolant, as needed. Repair any coolant leaks that are found. Stop.Test Step 3. Check Coolant Level Status on Cat ET
Connect the Caterpillar Electronic Technician (Cat ET) to the service tool connector.
Turn the keyswitch to the ON position. Start the engine and run the engine for 15 minutes.
Observe the status of "Coolant Level" on Cat ET.Expected Result:"Coolant Level" should read "OK".Note: The coolant level should be at the proper height.Results:
OK - The coolant level switch is sending the correct signal. Stop.
Not OK - Proceed to Test Step 4.Test Step 4. Short the Wires at the Switch
Illustration 3 g00702132
Breakout T
Turn the keyswitch to the OFF/RESET position.
Disconnect the J800/P800 coolant level switch connector.
Use a jumper to short P800:1 and P800:2.
Insert a "70-Terminal" Breakout T between ECM machine harness connector J1 and ECM machine harness connector P1.
Turn the keyswitch to the ON position. Do not start the engine.
Measure the voltage between P1:54 coolant level switch and P1:5 coolant level return at the breakout.
Remove the jumper.
Measure the voltage between P1:54 coolant level switch and P1:5 coolant level return at the breakout.
Turn the keyswitch to the OFF/RESET position. Expected Result:The voltage should be less than 0.5 VDC with the jumper installed. The voltage should be greater than 9.0 VDC when the jumper is removed.Results:
OK - The harness and the ECM are working properly. Temporarily replace the switch. Verify that the replacement of the switch solves the problem before permanently installing the switch. Stop.
Not OK - Proceed to Test Step 5.Test Step 5. Check for Shorts in the Harness
Illustration 4 g00702199
ECM connector P1
Disconnect the J1/P1 ECM connector.
Measure the resistance between P1:54 coolant level switch and P1:5 coolant level return. Measure the resistance between P1:54 and the remaining terminals.Expected Result:Results:
OK - Proceed to Test Step 6.
Not OK - There is a short in the harness. Repair the harness or replace the harness, as needed. Stop.Test Step 6. Check the Resistance Through the Harness
Use a jumper to short P800:1 to P800:2.
Measure the resistance between P1:54 coolant level switch and P1:5 coolant level return.Expected Result:Resistance should be less than 10 Ohms.Results:
OK - Proceed to Test Step 7.
Not OK - There is an open circuit or excessive resistance in the harness. Repair the harness or replace the harness, as needed. Stop.Test Step 7. Short the Switch Inputs at the ECM
Turn the keyswitch to the OFF/RESET position.
Insert a "70-Terminal" Breakout T at the J1/P1 ECM connector.
Use a jumper to short P1:54 coolant level switch and P1:5 coolant level return at the breakout.
Turn the keyswitch to the ON position. Do not start the engine.
Alternately remove the jumper and then insert the jumper. At the same time, watch the status screen on Cat ET.Expected Result: The status of the "Coolant Level" should change to "ON" with the jumper in place. The status of the "Coolant Level" should change to "OFF" when the jumper is removed from the circuit.Results:
OK - The ECM properly reads jumper inputs at P1 but not at the switch. The harness is faulty. Repair the harness or replace the harness, as needed. Stop.
Not OK - Repair: Correct switch inputs appear at the J1/P1 ECM connector, but the ECM is not reading the inputs properly. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM. Stop.