LINES GP-HEATER 2868891 - Caterpillar

Table 3
Troubleshooting Test Steps Values Results
5. Check the Output Voltage for the Air Shutoff Relay at the ECM
A. Ensure that the keyswitch is in the OFF position.
B. Disconnect the P1 ECM connector.
C. Fabricate a jumper wire that is long enough to reach from the P1-54 ECM connector to engine ground. Crimp a connector socket to one end of the jumper wire.
D. Remove the wire from terminal location P1-54 (overspeed verify switch) at the ECM connector. Insert the jumper wire into this terminal location.
E. Fabricate two other jumper wires that can be used as test leads at the ECM connector. Crimp a connector socket to one end of each jumper wire.
F. Remove the wires from terminal locations P1-11 (air shutoff solenoid) and P1-67 (solenoid return) at the ECM connector. Insert one of the jumper wires into each of these terminal locations.
G. Connect the J1/P1 ECM connectors.
H. Connect the loose end of the jumper wire that is in terminal location P1-54 to the engine ground stud.
I. Connect the leads of the voltage test lamp to the loose ends of the other two jumper wires that are in the P1 ECM connector.
J. Start the engine.
K. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint.
L. Stop the engine.
Output Voltage
Results: The test lamp illuminated.
Repair: The ECM is operating correctly. Perform the following procedure:
1. Verify the continuity of the ground circuit for the overspeed verify switch.
2. Isolate the overspeed verify switch from the circuit. Close the switch and measure the continuity across the switch. Open the switch and measure the continuity across the switch.
3. Verify the continuity of the circuit between the overspeed verify switch and the P1 ECM connector.
4. Restore the wiring to the original configuration.
If the overspeed verify that switch is OK and the circuit has continuity from the P1 and the engine ground stud, there is a problem in the wiring between the P1 ECM connector and the air shutoff relay. Repair the circuit connectors or wiring and/or replace the circuit connectors or wiring. Verify that the problem is resolved.
STOP
Results: The test lamp did not illuminate.
Repair: Restore the wiring to the original configuration. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".
STOP
Illustration 3 g00761537
Diode leads
Table 4
Troubleshooting Test Steps Values Results
6. Test the Diode for the Control Circuit
A. Disconnect the air shutoff relay's control wires at the relay.
B. Remove the diode from the air shutoff relay.
C. Select the "Diode Check" function on a digital voltmeter.
D. Place the red lead of the digital voltmeter on the diode at location (A). Place the black lead of the digital voltmeter on the diode at location (B).
E. Measure the voltage drop across the diode.
Diode
Results: The voltage drop across the diode is less than 1 V. The voltage drop across the diode is OK. Proceed to Test Step 7.
Results: The voltage drop across the diode is greater than 1 V.
Repair: The diode is damaged. Replace the diode. Verify that the problem is