3512B Generator Set Engine Caterpillar

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.

The secondary ECM has the ability to stop the engine by shutting off the inlet air supply in an emergency situation. The secondary ECM activates the output driver for the "Air Shutoff Switch (ASOS)". The "ASOS" energizes the two air shutoff solenoids. The solenoids trip the air shutoff valves.

There are two conditions which cause the engine control to activate the output driver for the "ASOS". The first condition occurs when the operator activates the customer's emergency stop. When the customer's emergency stop button is activated, the emergency stop inputs U and T to the primary ECM and the secondary ECM from the customer connector go high. The secondary ECM will recognize this change. The secondary ECM will energize the output driver for the "ASOS" for one second through the diode assembly.

The second condition occurs for an engine overspeed. If an engine overspeed occurs, the ECM will activate the output driver for the "ASOS" through the diode assembly. An overspeed can be simulated by using Caterpillar Electronic Technician (ET). In order to verify that the overspeed function is operable, the operator must access the screen for overriding parameters on Cat ET. When the override for the engine overspeed is set to the ON position, the setpoint for the engine overspeed is at 75% of the original setpoint. When the engine reaches the modified setpoint, the normal strategy for an engine overspeed is initiated.

Relays "R3A" and "R3" are energized through terminal 3 of the diode assembly. The relays are energized at the same time as the "ASOS" is energized. Terminal 3 of the diode assembly will energize relay "R3A" and relay "R3" for one second. The contacts of relay "R3" keep relay "R3A" and relay "R3" energized until power is cycled to the engine ECM. The contacts of relay "R3A" keep the coils of relay "R2" and relay "R2A" energized. When relays "R2" and "R2A" are energized, power is removed from the primary ECM and the secondary ECM. The primary ECM and the secondary ECM will power down. The injection signals to the injector solenoids will stop.

The contact of relay "R3A" also supplies power to terminal 3 of the connector for a timer. When power is applied to terminal 3 of the connector for the timer, the timer will activate. The timer outputs 24 VDC from terminal 6 of the connector for the timer for 2.5 seconds. The 24 VDC from the timer is applied to the coil of the "ASOS" and to terminal 2 of the diode assembly. The "ASOS" energizes the two air shutoff solenoids. The solenoids trip the air shutoff valves. The 2.5 second time limit for activation of the "ASOS" prevents damage to the air shutoff solenoids. A normally open switch at the air shutoff valves will close when the air shutoff solenoid activates the air shutoff valve. The switch inputs a signal to the primary ECM and to the secondary ECM. The signal notifies the primary ECM and the secondary ECM that the air shutoff valves are closed. The primary ECM and the secondary 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.

The "ASOS" can also be activated without the aid of the secondary ECM. When the local emergency stop switch on the instrument panel is depressed or the customer's remote emergency stop switch is activated, the coils of relay "R4" and relay "R4A" are energized. The contacts of relay "R4A" supplies power to terminal 3 of the connector for the timer and to the coils of relay "R2" and relay "R2A". When relays "R2" and "R2A" are energized, power is removed from the primary ECM and the secondary ECM. The circuit with the timer will operate in the same manner that was described above except that the emergency stop lamp on the instrument panel will illuminate and the relays "R3A" and "R3" will de-energize after 2.5 seconds. When relays "R3A" and "R3" de-energize, the overspeed indicator turns off.

Regardless of the reason for activation, the Engine Control Switch (ECS) must be turned to the OFF position for three seconds. This resets the ECM and the relays in the circuit. In addition to turning the ECS to the OFF position, the operator must determine the cause for the emergency shutdown before resetting the circuit. The operator must manually open the air shutoff valves before restarting the engine.

Illustration 1	g01645473
Typical example

Illustration 2	g01322302
Terminal locations for the following connectors A-C90/P-C1 Connectors for the power distribution panel, A-C2/J-C2/J-C1 Right hand cross over harness and C-C2/J-C1/J-C2 Left hand cross over harness (Terminal G) Drive for the air shutoff switch F708-BK(Black) (Terminal H) Return for the air shutoff solenoid H708-BK(Black) (Terminal I) Drive for the air shutoff solenoid G708-BK(Black)

Illustration 3	g01622856
Connector locations (1) A-C1/E-C2/E-C1 Right hand cross over harness (2) A-C2/J-C2/J-C1 Right hand cross over harness (3) A-C90/P-C1 Connectors for the power distribution panel (4) A-C91/P-C2 Connectors for the power distribution panel (5) A-C60 Connector for the prelube motor (6) A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel (7) C-C22 Primary ECM connector P2 (8) C-C15 Primary ECM connector P1 (9) C-C28 Secondary ECM connector P2 (10) C-C29 Secondary ECM connector P1 (11) C-C47 Connector for the power relay panel (12) C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel (13) C-C18/(TB-C1 customer or L-C1/L-C2 EMCP 3) connectors (14) C-C2/J-C1/J-C2 Left hand cross over harness (15) C-C1/E-C1/E-C2 Left hand cross over harness

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the circuit breaker for the battery to the OFF position.

2. Turn the ECS to the OFF position.

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors that are associated with the circuit. Check the allen head screw on each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.

5. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion or of pinch points.

Results:

• OK - The harness and wiring appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem in the connectors and/or wiring.

  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. Test the Air Shutoff System

1. Turn the circuit breaker for the battery to the ON position.

2. Turn the ECS to the STOP position.

3. Activate the customer's emergency stop switch.

4. Monitor the air shutoff solenoids.

5. Deactivate the customer's emergency stop switch.

Expected Result:

The air shutoff solenoids activated.

Results:

• OK - The air shutoff solenoids activated correctly.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The air shutoff solenoids failed to activate. Proceed to Test Step 3.

Test Step 3. Check for the Voltage from the "ASOS" at the Connector P-C1/A-C90 for the Power Distribution Panel

1. Turn the ECS to the STOP position.

2. Remove wire G708-BK(Black) from terminal "I" of connector A-C90. Install a wire jumper into the connector for wire G708-BK(Black).

3. Reconnect the P-C1/A-C90 connector.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the wire jumper in terminal I at connector A-C90 of the rigid harness. Refer to Illustration 2 for terminal locations.

6. Deactivate the customer's emergency stop switch.

7. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point. Proceed to Test Step 7.

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds. Proceed to Test Step 4.

Test Step 4. Test for Voltage to the Coil of the "ASOS" at the Connector A-C90 for the Power Distribution Panel

1. Remove wire F708-BK(Black) from terminal "G" of connector A-C90.

2. Turn the ECS to the STOP position.

3. Activate the customer's emergency stop switch.

4. Monitor the voltage on wire F708-BK(Black).

5. Deactivate the customer's emergency stop switch.

6. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately one second.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately one second. The circuit is operating correctly to this point. Proceed to Test Step 5.

• Not OK - No voltage was measured. Proceed to Test Step 14.

Test Step 5. Test for Voltage to the Coil of the "ASOS"

1. Turn the ECS to the OFF position.

2. The input to the coil of the "ASOS" is wire T708-BK(Black) from the diode assembly. Remove wire T708 from the coil of the "ASOS". Connect a voltmeter between wire T708-BK(Black) and the engine ground.

   Note: The "ASOS" is turned on for one second by the ECM. The timer keeps the "ASOS" energized for approximately 2.5 seconds.

3. Turn the ECS to the STOP position.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

7. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point. Proceed to Test Step 6.

• Not OK - No voltage was measured. Proceed to Test Step 10.

• Not OK - The voltage did not measure 24 ± 3 VDC for 2.5 seconds. Proceed to Test Step 8.

Test Step 6. Check for Voltage from the "ASOS" to the Air Shutoff Solenoids

1. Turn the ECS to the OFF position.

2. Disconnect wire G708-BK(Black) from the "ASOS".

3. Connect a voltmeter to the empty terminal on the "ASOS". Connect the other lead of the voltmeter to engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Reconnect wire G708-BK(Black) to the "ASOS".

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point.

  Repair: Repair the wire G708-BK(Black) between the "ASOS" and terminal I at connector P-C1 of the power distribution panel.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds.

  Repair: Verify that 24 ± 3 VDC is present on wire K708-BK(Black) at the normally open contacts of the "ASOS". If voltage is not present on wire K708-BK(Black), check the wiring and the circuit breaker for the air shutoff for problems.

  Check wire 220-BK(Black) on the coil of the "ASOS" for continuity to the −Battery. If necessary, repair the wire or replace the wire.

  If wire 220-BK(Black) is OK and voltage is present on wire K708-BK(Black), replace the "ASOS".

  STOP

Test Step 7. Check the Voltage at the Connector for the Air Shutoff Solenoids

1. Turn the ECS to the OFF position.

2. Disconnect the connector for the air shutoff solenoids. Disconnect the connector for the right and left sides of the engine.

3. Connect a voltmeter between wire G708-BK(Black) on the connector for the air shutoff solenoid and the engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Reconnect the connectors for the air shutoff solenoids.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point.

  Repair: Check the wire H708-BK(Black) from terminal A of the connector for the air shutoff solenoid for continuity to the −Battery terminal. If the wire H708-BK(Black) to the −Battery terminal is OK, replace the air shutoff solenoid.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds. System voltage was not available at the solenoid connector.

  Repair: Repair the wire G708-BK(Black) between the connector for the air shutoff solenoids and terminal I at connector A-C90 of the rigid harness. Refer to Illustration 1 for a schematic of the circuit.

  STOP

Test Step 8. Check the Voltage at the Contact of Relay "R3A"

1. Turn the ECS to the OFF position.

2. Disconnect wire T120-BK(Black) from terminal 87 of relay "R3A".

3. Connect a voltmeter between terminal 87 of relay "R3A" and the engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Reconnect wire T120-BK(Black).

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 9.

• Not OK - The voltage did not measure 24 ± 3 VDC. Proceed to Test Step 11.

Test Step 9. Check the Voltage at Terminal 6 of the Connector for the Timer

1. Turn the ECS to the OFF position.

2. Remove wire T708 from terminal 6 of the connector for the timer.

3. Connect a voltmeter between terminal 6 of the connector for the timer and engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. Proceed to Test Step 12.

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds.

  Repair: Check for 24 ± 3 VDC on terminal 3 of the connector for the timer. If voltage is not present on terminal 3, repair the wire T120-BK(Black) between terminal 87 of relay "R3A" and terminal 3 of the connector for the timer.

  If voltage is present on terminal 3 of the connector for the timer, verify that wire 220-BK(Black) on terminal 2 of the connector for the timer has continuity to the −Battery. If wire 220-BK(Black) does not have continuity to the −Battery, repair the wire.

  Verify that 24 ± 3 VDC is present on terminal 1 of the connector for the timer. If 24 ± 3 VDC is not present on terminal 1 of the connector for the timer, verify that the engine control switch is not in the "OFF" position. Verify that the "MPD" breaker is not tripped. Check the normally closed contact of relay "R1" for proper operation. Check the wire 120 between terminal 1 of the connector for the timer and relay "R1" for damage. Check the wire A120 between relay "R1" and the "MPD" breaker for damage. If necessary, repair the wires.

  If the voltage is present on terminal 1 and terminal 3 of the timer and wire 220-BK(Black) is OK, replace the timer.

  STOP

Test Step 10. Check the Voltage at Terminal 4 of the Connector for the Diodes

1. Turn the ECS to the OFF position.

2. Remove wire T708 from terminal 4 of the connector for the diodes.

3. Connect a voltmeter between terminal 4 of the connector for the diodes and the engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately one second.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately one second.

  Repair: Repair the wire T708 between the connector for the diodes and the "ASOS". Return all wiring to the original configuration.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately one second.

  Repair:

  1. Turn the ECS to the OFF position.

  2. Connect a voltmeter between terminal 1 of the connector for the diodes and the engine ground.

  3. Turn the ECS to the STOP position.

  4. Activate the customer's emergency stop switch.

  5. Monitor the voltage on the voltmeter.

  6. Deactivate the customer's emergency stop switch.
  If the voltage measures 24 ± 3 VDC for approximately one second, replace the diodes.

  If the voltage does not measure 24 ± 3 VDC for approximately one second, repair the wire F708-BK(Black) between the connector for the diodes and wire F708-BK(Black) on pin G at connector A-C90 of the right rail. Return all wiring to the original configuration.

  STOP

Test Step 11. Check the Voltage at the Coil of Relay "R3A"

1. Turn the ECS to the OFF position.

2. Remove wire 918-BK(Black) from terminal 86 of relay "R3A".

3. Connect a voltmeter between wire 918-BK(Black) and the engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Check wire 220-BK(Black) on the coil of the "R3A" relay for continuity to the −Battery. If necessary, repair the wire or replace the wire.

  Check for 24 ± 3 VDC on wire 120-BK(Black) on terminal 30 of relay "R3A". If 24 ± 3 VDC is not present on wire 120-BK(Black), verify that the engine control switch is not in the "OFF" position. Verify that the "MPD" breaker is not tripped. Check the normally closed contact of relay "R1" for proper operation. Check the wire 120-BK(Black) between terminal 30 of the relay "R3A" and relay "R1" for damage. Check the wire 120-BK(Black) between relay "R1" and the "MPD" breaker for damage. If necessary, repair the wires.

  If wire 220-BK(Black) is OK and voltage is present on wire 120-BK(Black) on terminal 30, replace relay "R3A".

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC. Proceed to Test Step 13.

Test Step 12. Check the Voltage to Terminal 2 of the Connector for the Diodes from the Timer

1. Turn the ECS to the OFF position.

2. Remove wire T708 from terminal 2 of the connector for the diodes.

3. Connect a voltmeter between wire T708 and the engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 13.

• Not OK - The voltage did not measure 24 ± 3 VDC.

  Repair: Repair the wire T708-BK(Black) between the diodes and the timer.

  STOP

Test Step 13. Check the Voltage from Terminal 3 of the Connector for the Diode Assembly

1. Turn the ECS to the OFF position.

2. Remove wire 918 from terminal 3 of the connector for the diodes.

3. Connect a voltmeter between terminal 3 of the connector for the diode assembly and the engine ground.

4. Turn the ECS to the STOP position.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Repair the wire 918-BK(Black) between the diodes and relay "R3A".

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC.

  Repair: Replace the diodes.

  STOP

Test Step 14. Check the Output Driver for the Air Shutoff System at the ECM

1. Turn the ECS to the OFF position.

2. Disconnect the secondary ECM connector P2.

3. Remove wire F708-BK(Black) from ECM connector P2-13. Install a wire jumper into P2-13.

4. Reconnect ECM connector P2.

5. Connect a voltmeter between the wire jumper in P2-13 and engine ground.

6. Turn the ECS to the STOP position.

7. Activate the customer's emergency stop switch.

8. Monitor the voltage on the voltmeter.

9. Deactivate the customer's emergency stop switch.

10. Return all wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC for one second.

Results:

• OK - The voltage measures 24 ± 3 VDC for one second.

  Repair: Repair the wire F708-BK(Black) between the ECM connector and terminal G at connector A-C90 of the rigid harness. Refer to Illustration 1 for a schematic of the circuit. Check for voltage at the following connectors A-C2/J-C2/J-C1 Right hand cross over harness and C-C2/J-C1/J-C2 Left hand cross over harness .

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC.

  Repair: Monitor the status screen for the emergency stop in order to verify that the ECM is receiving the emergency stop signal. If the ECM is receiving the emergency stop signal from the customer connector, replace the ECM. If the ECM is not receiving the emergency stop signal from the customer connector, repair the wiring between the ECM and the customer connector.

  STOP