3512C Petroleum Engines with Dynamic Gas Blending Caterpillar

Use this procedure in order to troubleshoot the emergency stop system. Or, use this procedure if the following diagnostic code is active or easily repeated.

Table 1

Diagnostic Codes Table
J1939 Code and Description	Conditions which Generate this Code	System Response
970-2 Engine Auxiliary Engine Shutdown Switch : Erratic, Intermittent, or Incorrect	The two inputs from the emergency stop switch are in the opposite state.	The code is logged.

The Electronic Control Module (ECM) receives two signals from the emergency stop switch. The signals allow the ECM to determine the status of the emergency stop switch. The ECM will shut down the engine when both of the signals are open. When both of the signals are connected to the −Battery the emergency stop switch is not active, and the engine will run.

If two different signals are detected during the powerup, the ECM will determine that one of the signals is incorrect. A diagnostic code will be logged and a diagnostic code will remain active. The engine will continue to run when the ECM detects two different signals. If both of the signals are open, the engine will stop.

The customer can install multiple emergency stop switches. When the Engine Control Switch (ECS) is turned to the ON position, the engine will begin the sequence for start-up.When the emergency stop switch is activated, the ECM will stop firing the injectors. The engine will stop. When an emergency stop is received by the ECM, the ECM will activate the output for the solenoid valve that controls the air shutoff valve. When the solenoid valve activates, the air shutoff valve closes removing the intake air to the engine. Manually open the air shutoff valve in order to start the engine.

Note: The air shutoff is optional. Set the programmable parameter with Caterpillar Electronic Technician (ET) in order to enable the air shutoff.

The 970-31 Engine Auxiliary Engine Shutdown Switch event code will be set when the remote emergency stop switch is activated. This event will prevent engine operation. Electrical power to the ECM must be removed for three seconds in order to clear this event.

Illustration 1	g03382536
Emergency stop schematic

Illustration 2	g03393097
P1 ECM connector (P1-5) Digital return (P1-19) Air shutoff relay (P1-23) E-Stop 1 (P1-40) Start/Run/Stop 1 (P1-52) +Battery (P1-53) +Battery (P1-54) Start/Run/Stop 2 (P1-55) +Battery (ECM) (P1-56) E-Stop 2 (P1-61) −Battery (P1-62) Air shutoff feedback (P1-63) −Battery (P1-70) Keyswitch

Illustration 3	g03393098
Customer connector (Terminal 01) +Battery (Terminal 02) +Battery (Terminal 04) Air shutoff (Terminal 09) Digital return (Terminal 16) E-Stop 1 (Terminal 17) E-Stop2 (Terminal 23) Start/Run/Stop 1 (Terminal 24) Start/Run/Stop 2 (Terminal 27) Keyswitch (Terminal 34) −Battery (Terminal 35) −Battery

Table 2

Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Verify that the air shutoff mechanisms are set to the OPEN position. C. Thoroughly inspect the ECM connectors. Also, inspect the connectors at the air shutoff mechanism that are for the solenoids. Also, inspect the switches for the air shutoff. Refer to Troubleshooting, "Electrical Connectors - Inspect" D. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the air shutoff system. E. Check the allen head screw on each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. F. Check the harness and the wiring for abrasion and for pinch points from the air shutoff solenoid to the ECM.	Connectors	Result: The connectors and wiring appear to be OK. Proceed to Test Step 2. Result: The connectors and/or wiring are Not OK. Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the repair eliminated the problem.
2. Test the Operation of the Control Solenoid for the Air Shutoff Relay and Check for Logged Codes A. Connect Cat ET to the service tool connector. B. Restore the electrical power to the ECM. C. Test the air shutoff system with the emergency stop switch: a. Start the engine. b. Place the emergency stop switch in the STOP position. c. Check the position of the air shutoff mechanisms. Activation of the emergency stop will activate the air shutoff system and the air shutoff mechanisms will close. Check that the solenoid has de-energized after the air shutoff mechanisms are closed. d. Turn the main disconnect switch to the OFF position. D. Check the status of the "Air Intake Shutoff Position" parameter in Cat ET. a. While the air shutoff mechanisms are shut, check the status of the "Air Intake Shutoff Position" parameter in Cat ET. Note: Wait at least 30 seconds in order for diagnostic codes to become active. b. Reset the air shutoff mechanisms. Check the status of the "Air Intake Shutoff Position" parameter in Cat ET while the air shutoff mechanisms are open. E. Use Cat ET to check for logged diagnostic codes. Check if the following codes are logged: - 970-2 F. Reset the air shutoff mechanisms for the air shutoff to the open position. - Place the emergency stop switch in the RUN position. - Turn the main disconnect switch to the OFF position. - Restore the wiring to the original configuration.	Codes	Result: The valve mechanisms are operating correctly. There are no diagnostic codes that are logged during the test. Repair: The air shutoff system appears to be operating correctly. The original problem seems to be resolved. There may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent problems. Result: The valve mechanism did not close when the emergency stop switch is activated. There is a logged 970-2 diagnostic code. Proceed to Test Step 3.
3. Check the Voltage at the Emergency Stop Switch (Customer) A. Remove the wire from the output terminal at the connector for the emergency stop switch. B. Restore the electrical power to the ECM. C. Connect a voltmeter between the output terminal of the emergency shutdown switch and the −Battery. D. As the emergency stop switch is activated, measure the voltage at the output of the switch. - Place the emergency stop switch in the RUN position. - Turn the main disconnect switch to the OFF position. - Restore the wiring to the original configuration.	24 ± 3 VDC	Result: The voltage is 24 ± 3 VDC. The output from the emergency stop switch is correct. Proceed to Test Step 4. Result: The voltage is not 24 ± 3 VDC at the output of the emergency stop switch. Repair: There is a problem with the emergency stop switch. There may be a problem in the circuit for the supply voltage to the switch. Perform the following procedure: 1. Check that the main circuit breaker is not thrown. Reset the breaker, if necessary. 2. Isolate each circuit and check for 24 ± 3 VDC. Note: During the measurements, ensure that the electrical power is restored to the ECM. Ensure that the emergency stop switch is activated. Place the emergency stop switch in the RUN position. Turn the main disconnect switch to the OFF position. Restore the wiring to the original configuration. If voltage is 24 ± 3 VDC at the connector for the emergency stop switch, there is a problem with the emergency stop switch. Replace the switch. Verify that the repair eliminates the problem. If voltage is not 24 ± 3 VDC at one of the test locations, the problem is in the wiring. Repair the harness. Replace the harness, if necessary. Verify that the repair eliminates the problem.
4. Check the Harness Between the Emergency Stop Switch and the Air Shutoff Solenoid A. Remove the connector from the air shutoff solenoid. B. Restore the electrical power to the ECM. C. Connect a voltmeter between the return terminal and the control coil voltage terminal on the harness side of the connector at the solenoid. D. As the emergency stop switch is activated, measure the voltage at the connector. - Place the emergency stop switch in the RUN position. - Turn the main disconnect switch to the OFF position. - Restore the wiring to the original configuration.	24 ± 3 VDC for 2.5 seconds	Result: The voltage is 24 ± 3 VDC for 2.5 seconds. Repair: The harness between the emergency stop switch and the air shutoff solenoid is OK. There may be a problem with the air shutoff solenoid. Perform the following procedure: 1. Disconnect the connector from the solenoid. Use a multimeter to check the resistance of the coil across the output terminal and the control coil voltage terminal at the solenoid connector. The correct resistance of the coil is approximately 33 Ohms at a temperature of 25 °C (77 °F). If the condition of the solenoid is suspect, replace the solenoid. 2. Verify the mechanical condition of the air shutoff mechanisms. Ensure that the air shutoff mechanisms close freely without binding. Check that adequate oil pressure is reaching the valve assemblies. Perform any necessary repairs. 3. Check that the return circuit has continuity from the terminal of the solenoid connector to −Battery. Perform any necessary repairs. 4. Verify that any repairs eliminate the original problem. Place the emergency stop switch in the RUN position. Turn the main disconnect switch to the OFF position. Restore the wiring to the original configuration. Proceed to Test Step 5.
5. Check for Proper Operation of the ECM A. Disconnect the J1/P1 ECM connectors. B. 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. C. Remove the wire from terminal location P1-19 (air shutoff) at the ECM connector. Install the jumper wire into this terminal location. D. Connect the J1/P1 ECM connectors. E. Restore the electrical power to the ECM. F. Measure the voltage between the jumper wire and the engine ground stud while you place the remote emergency stop switch in the STOP position. G. Turn the main disconnect switch to the OFF position. Restore the wiring to the original configuration.	ECM	Result: When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for one second. Repair: There may be a problem with the control circuit for the air shutoff. Refer to Troubleshooting, "Air Shutoff - Test". Result: When the remote emergency stop switch is placed in the STOP position, the voltage is not 24 ± 3 VDC for one second. Repair: The ECM is not reading the correct status for the switches. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. Verify that the repair eliminates the problem.