PLATE 5259798 - Caterpillar

the timer and the relay is OK. The problem is with the air shutoff relay's secondary circuit or the relay. Proceed to Test Step 8.
Not OK - The voltage is not 24 3 VDC for 2.5 seconds.Repair: There is voltage at the output of the timer but not at the control input of the relay. The problem is in the harness between the air shutoff timer and the air shutoff relay. The problem may be in a connector. Repair the harness and/or the connector. Replace parts, if necessary. Verify that the original problem has been corrected.STOPTest Step 6. Check the Harness Between the Air Shutoff Relay and the ECM
Remove the wire connection from the control input at the air shutoff relay.
Turn the battery disconnect switch to the ON position.
Start the engine and allow the engine to run at low idle.
Use Cat ET to activate the "Overspeed Verify" feature. Wait at least 30 seconds for activation of the feature.
Increase engine speed to the rated speed of the engine.
As the engine speed increases above 75 percent of the rated engine speed, measure the voltage between the loose wire at the air shutoff relay and the engine ground stud.
Stop the engine. Turn the battery disconnect switch to the OFF position.Restore the wiring to the original configuration.Expected Result:As the engine speed increases above 75 percent of the rated engine speed, the voltage is 24 3 VDC.Results:
OK - The voltage is 24 3 VDC when the engine speed increases above 75 percent of the rated engine speed. The ECM and the wiring to the air shutoff relay are OK. The problem is with the air shutoff relay's secondary circuit or the relay. Proceed to Test Step 8.
Not OK - The voltage is not 24 3 VDC when the engine speed increases above 75 percent of the rated engine speed. There is a problem in the circuit between the ECM and the air shutoff relay. There may be a problem with the ECM. Proceed to Test Step 7.Test Step 7. Check the ECM Output for the Air Shutoff Relay at the ECM
Disconnect J1/P1 ECM connector.
Fabricate a jumper wire that is long enough to use as a test lead at the ECM connector. Crimp a connector socket to one end of the jumper wire.
Remove the wire from terminal location P1-10 (air shutoff) at the ECM connector. Install the jumper wire into this terminal location.
Connect the J1/P1 ECM connectors.
Start the engine.
Use Cat ET to activate the "Overspeed Verify" feature. Wait at least 30 seconds for activation of the feature.
Increase engine speed to the rated speed of the engine.
As the engine speed increases above 75 percent of the rated engine speed, measure the voltage between the loose wire at the air shutoff relay and the engine ground stud. Note: The ECM applies a voltage to the circuit for approximately one second. Run the test as many times as necessary in order to verify that a voltage is present at this output. The emergency