Use this procedure in order to troubleshoot the air shutoff system or use this procedure if any one of the diagnostic codes in Table 1 is active or easily repeated.
| Diagnostic Codes Table | ||
|---|---|---|
| Code and Description | Conditions which Generate this Code | System Response |
| 446-5 Air Shutdown Relay current below normal | The Electronic Control Module (ECM) detects low current in the circuit. The ECM can only detect this condition when the output driver is not activated. | The code is logged. |
| 446-6 Air Shutoff Relay short | The ECM detects excessive current flow in the circuit. The ECM can only detect this condition when the output driver is activated. | |
| E2087(3) Air Intake Shutoff Closed | The ECM detects an "Active" condition in the detection circuit that monitors the state of the air shutoff valves. The configurable parameter for the air shutoff system is set to "Installed". | The code is latched until power is cycled to the ECM. The process for starting the engine will be stopped and the process for starting the engine will be disabled. If engine rpm is present, the air shutoff relay will be activated. The code is logged. |
| E2088(1) Air Intake Shutoff Detection Circuit Detected but Not Installed | The ECM detects an "Active" condition in the detection circuit that monitors the state of the air shutoff valves. The configurable parameter for the air shutoff system is set to "Not Installed". | The code is logged. |
A normally closed switch at the air shutoff valves will open when the air shutoff solenoid activates the air shutoff valve. The switch input to the ECM notifies the ECM that the air shutoff valves are closed. The ECM will not send injection signals to the injector solenoids until the switch inputs from the air shutoff valves indicate that the valves are open. If the circuit indicates that the air shutoff valves are closed, the ECM will generate the E2087 event code.
Note: The air shutoff is optional. A programmable parameter needs to be set to "Installed" with Caterpillar Electronic Technician (ET) in order to enable the air shutoff system. If the air shutoff system is installed on the engine but the configurable parameter is not set to "Installed", the ECM will detect the air shutoff system through the normally closed switches on the air shutoff valves. If this happens the E2088(1) event code will be generated.
The ECM has the ability to stop the engine in an emergency situation by shutting off the air supply to the engine. The ECM activates a relay which energizes two air shutoff solenoids. The solenoids trip the air shutoff valves.
There are three conditions which can cause the ECM to activate the air shutoff:
Engine Overspeed - The first condition occurs when the ECM detects an engine overspeed. During an engine overspeed, the ECM energizes the air shutoff relay. The ECM supplies voltage to the air shutoff relay for one second. The output of the relay will energize the air shutoff solenoids in order to shut down the engine. Once an event for the air shutoff system is activated, the event is latched until electrical power to the ECM system is cycled.
Overspeed Verify Feature - The second condition occurs when the overspeed verify feature is initiated with Cat ET. This feature will energize the air shutoff relay when the engine speed is increased above 75 percent of the rated engine speed. The ECM supplies voltage to the air shutoff relay for one second during the shutdown. The overspeed verify feature can be initiated in order to test the operation of the air shutoff system.
Remote Emergency Stop Switch - The third condition occurs when the remote emergency stop switch is activated. When the remote emergency stop switch is placed in the STOP position, the switch inputs at J1-23 and J1-28 are opened. The ECM supplies voltage to the air shutoff relay for one second during the shutdown. The remote emergency stop can be activated in order to test the operation of the air shutoff system.
The air shutoff relay can also be activated without the aid of the ECM. When the customer's emergency stop switch is placed in the STOP position, voltage is supplied to the relay control for the ECM relay. The ECM relay removes electrical power from the ECM. Voltage is also supplied to the air shutoff timer. The air shutoff timer supplies voltage to the air shutoff relay for 2.5 seconds. This latches the air shutoff valves in the closed position. The timer has been placed in the circuit in order to prevent the shutoff solenoids from being powered for extended periods.
After the air shutoff mechanism has been tripped the following actions must be taken in order to start the engine:
- A manual reset of the valve mechanism is necessary.
- Verify that the switches that detect air shutoff are closed.
- Remove electrical power from the ECM for 3 seconds in order to reset any event codes that are latched.
 | |
| Illustration 1 | g01443822 |
Schematic for the air shutoff system | |
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| Illustration 2 | g01444508 |
Location of the ECM connectors (1) J2/P2 ECM connectors (2) J1/P1 ECM connectors | |
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| Illustration 3 | g01210157 |
Air shutoff mechanism (typical example) (3) Terminals for the air shutoff solenoid | |
 | |
| Illustration 4 | g01444514 |
P1 ECM connector (P1-23) Remote emergency stop (signal 1) (P1-28) Remote emergency stop (signal 2) (P1-52) +Battery (P1-53) +Battery (P1-55) +Battery (P1-56) Air shutoff switch (P1-63) −Battery (P1-65) −Battery (P1-67) −Battery (P1-70) Keyswitch | |
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| Illustration 5 | g01444518 |
(P2-13) Digital return (P2-66) Drive for the air shutoff | |
 | |
| Illustration 6 | g01209281 |
Terminal locations for the air shutoff timer (1) +Battery (2) −Battery (3) Control (6) Load | |
 | |
| Illustration 7 | g01444669 |
Generator connector (Terminal 4) auxiliary power (Terminal 5) auxiliary power (Terminal 15) Digital return (Terminal 17) E-Stop 2 (Terminal 18) Keyswitch (Terminal 19) E-Stop 1 (Terminal 23) Timer/Shutdown | |
Test Step 1. Inspect the Electrical Connectors and the Wiring
- Turn the Engine Control Switch (ECS) to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Verify that the air shutoff mechanisms are set to the OPEN position.
- Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect connections (3) at the air shutoff solenoid. Refer to Troubleshooting, "Electrical Connectors - Inspect".
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the air shutoff system.
- 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.
- Check the harness and the wiring for abrasion and for pinch points from the air shutoff solenoid to the ECM.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - The connectors and wiring appear to be OK. Proceed to Test Step 4.
- Not OK - 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 completely coupled. Verify that the problem is resolved.
STOP
Test Step 2. Check for "Active" Diagnostic Codes or for "Active" Event Codes
- Connect Cat ET to the service tool connector.
- Turn the main disconnect switch to the ON position. Turn the ECS to the STOP position.
- Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Determine if a diagnostic code has occurred several times.
Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal. The problem may be caused by moisture, corrosion, or wear.
- Determine if the problem is active and related to one of the following diagnostic codes:
- 446-5
- 446-6
- E2087
- E2088
- 446-5
Expected Result:
A diagnostic code or an event code is not active.
Results:
- OK - A diagnostic code or an event code is not active.
Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - A E2088 event code is active. The configurable parameter for the air shutoff is set to "Enabled". The configurable parameter "Air Inlet Shutoff Detection" is set to "Not Installed".
Repair: Go to Troubleshooting, "Configuration Parameters". Set the parameter for the "Air Inlet Shutoff Detection" to "Installed". Clear the event code.
STOP
- Not OK - A E2087 event code is active.
Repair: Verify that the air shutoff valves are in the closed position. If the air shutoff valves are in the closed position, determine the reason for activation of the air shutoff system. After the reason for the air shutoff system's activation has been resolved, remove power from the ECM. Manually open the air shutoff valves. Restore power to the ECM and check for an active E2087 event code. If the air shutoff valves are in the open position and the E2087 event code is active, go to the following test step.
Proceed to Test Step 3.
- Not OK - A 446-5 event code or a 446-6 diagnostic code is active. Proceed to Test Step 4.
Test Step 3. Check the Detection Circuit for the Air Shutoff System
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Disconnect the ECM connector J1/P1.
- Check continuity between terminals P1-55 and P1-56 on ECM connector P1.
- Check the continuity between switch terminals at each air shutoff valve.
- Each continuity check should indicate a closed circuit.
- If a continuity check indicates an open circuit, repair the wiring and/or replace the switch(s).
- If the E2087 event code is still active after repairing any wiring or repairing any switch, disconnect the wiring from ECM terminals P1-55 and P1-56. Ensure that the wires are not touching engine ground or any other wire in the harness.
- Install wire jumpers into the terminals for the air shutoff switches. Create a short circuit between the wire jumpers that were just installed.
- Reconnect ECM connector J1/P1.
- Restore electrical power to the ECM.
- Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Expected Result:
The E2087 event code is no longer active.
Results:
- OK - The E2087 event code is no longer active.
Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - The E2087 event code is still active.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".
STOP
Test Step 4. Test the Operation of the Control Solenoid for the Air Shutoff Relay
- Turn the main disconnect switch to the ON position. Turn the ECS to the STOP position.
- Check the position of the air shutoff valves. Activation of the remote emergency stop will activate the air shutoff system and the valve mechanisms will close.
Expected Result:
The valve mechanisms operate correctly at this time.
Results:
- OK - The valve mechanisms are operating correctly.
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 the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent problems.
STOP
- Not OK - - The valve mechanisms do not close when the remote emergency stop switch is activated. Proceed to Test Step 5.
Test Step 5. Check the Harness Between the Air Shutoff Relay and the ECM
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Remove the wire connection from the control input at the air shutoff relay.
- Turn the main disconnect switch to the ON position. Turn the ECS to the STOP position.
- Measure the voltage between the loose wire at the air shutoff relay and the engine ground stud while you place the remote emergency stop switch in the STOP position.
Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
Restore the wiring to the original configuration.
Expected Result:
When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Results:
- OK - When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second. 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 7.
- Not OK - When the remote emergency stop switch is placed in the STOP position, the voltage is not 24 ± 3 VDC for 1 second. 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 6.
Test Step 6. 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 P2-13 (air shutoff) at the ECM connector. Install the jumper wire into this terminal location.
- Connect the J1/P1 ECM connectors.
- Turn the main disconnect switch to the ON position. Turn the ECS to the STOP position.
- Measure the voltage between the jumper wire and the engine ground stud while you place the remote emergency stop switch in the STOP position.
- Stop the engine.
Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
Restore the wiring to the original configuration.
Expected Result:
When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Results:
- OK - When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Repair: There is an electrical problem in the harness between the ECM and the air shutoff relay. The problem may be in a connector. Repair the harness and/or the connectors. Replace parts, if necessary. Verify that the original problem is resolved.
STOP
- Not OK - When the remote emergency stop switch is placed in the STOP position, the voltage is not 24 ± 3 VDC for 1 second.
Repair: The ECM is not responding to the overspeed condition. There is a problem with the ECM. Replace the ECM. Refer to the electronic troubleshooting procedure Troubleshooting, "ECM -Replace" for information that is related to ECM replacement.
STOP
Test Step 7. Check the Relay Output at the Air Shutoff Solenoids
- Remove the supply wires from the terminals of each air shutoff solenoid.
- Measure the voltage between the supply wires for the air shutoff solenoids and the engine ground stud while you place the remote emergency stop switch in the STOP position.
Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
Restore the wiring to the original configuration.
Expected Result:
When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Results:
- OK - When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Repair: The air shutoff solenoids are receiving the correct voltage. There may be a problem in the ground circuit to the air shutoff solenoids or the solenoids and/or the valve mechanisms may not be operating correctly. Perform the following procedure:
- Check the ground circuit to the air shutoff solenoid:
- Remove the ground wire from the air shutoff solenoid.
- Turn the main disconnect switch to the ON position.
- Check continuity of the ground circuit from the solenoid to the battery.
If continuity does not exist in the ground circuit to the air shutoff solenoid, repair the circuit.
- Check the mechanical condition of the valve mechanisms.
- Visually inspect the mechanical condition of the valve mechanisms.
- Manually operate the valve mechanisms. Check that the mechanisms are operating freely. Check the mechanisms for binding.
If a mechanical problem with the valve mechanisms is suspected, repair the mechanisms. Replace parts, if necessary.
- Check the electrical condition of the solenoids:
- Use 24 ± 3 VDC to test the operation of the solenoids.
If the solenoids are not operating correctly, replace the solenoids.
- Use 24 ± 3 VDC to test the operation of the solenoids.
STOP
- Check the ground circuit to the air shutoff solenoid:
- Not OK - When the remote emergency stop switch is placed in the STOP position, the voltage is not 24 ± 3 VDC for 1 second. The air shutoff solenoids are not receiving the correct voltage. Proceed to Test Step 8.
Test Step 8. Test the Output Voltage at the Air Shutoff Relay
- Remove the wire from the terminal of the air shutoff relay that is for the secondary output to the air shutoff solenoids.
- Turn the main disconnect switch to the ON position. Turn the ECS to the STOP position.
- Measure the voltage between the secondary output terminal of the air shutoff relay and the engine ground stud while you place the remote emergency stop switch in the STOP position.
Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
Expected Result:
When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Results:
- OK - When the remote emergency stop switch is placed in the STOP position, the voltage is 24 ± 3 VDC for 1 second.
Repair: The voltage is present at the output of the relay, but not at the solenoid. There is an electrical problem in the harness between the air shutoff relay and the air shutoff solenoids. The problem may be in a connector. Repair the harness and/or the connectors. Replace parts, if necessary. Verify that the original problem is resolved.
STOP
- Not OK - When the remote emergency stop switch is placed in the STOP position, the voltage is not 24 ± 3 VDC for 1 second. The secondary output of the air shutoff relay is not supplying the correct voltage. There may be a problem with the relay. Proceed to Test Step 9.
Test Step 9. Check the Supply Voltage to the Air Shutoff Relay
- Remove the wire from the supply to the secondary circuit of the air shutoff relay.
- Turn the main disconnect switch to the ON position. Turn the ECS to the STOP position.
- Measure the voltage between the supply wire and the engine ground stud.
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
Expected Result:
The voltage is 24 ± 3 VDC.
Results:
- OK - The voltage is 24 ± 3 VDC.
Repair: The air shutoff relay is not operating correctly.There may be a problem in the ground circuit for the control input of the air shutoff relay. The problem may be with the air shutoff relay. Perform the following procedure:
- Remove the ground wire from the air shutoff relay.
- Turn the main disconnect switch to the ON position.
- Check the continuity of the ground circuit from the relay to the battery.
STOP
- Not OK - The voltage is not 24 ± 3 VDC .
Repair: The problem is in the supply circuit to the air shutoff relay. Ensure that the circuit breaker for the air shutoff relay has not tripped. Repair the circuit. Replace parts, if necessary. Verify that the repair resolved the original problem.
STOP