3512B Generator Set Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with a sensor supply or if any one of the diagnostic codes in Table 1 is active or easily repeated.

System Operation

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

• Aftercooler temperature sensor

• Atmospheric pressure sensor

• Coolant pressure sensor

• Coolant temperature sensor

• Crankcase pressure sensor

• Filtered engine oil pressure sensor

• Filtered fuel pressure sensor

• Turbocharger outlet pressure sensor

• Left turbocharger inlet pressure sensor

• Right turbocharger inlet pressure sensor

• Unfiltered engine oil pressure sensor

• Unfiltered fuel pressure sensor

Both the primary ECM and the secondary ECM can provide analog power and analog sensor reference to the engine sensors. In normal operation, the primary ECM has control of the engine. The primary ECM will provide the analog power and the analog sensor reference to the engine sensors. If the secondary ECM must take over control of the engine, the secondary ECM will provide analog power and the analog sensor reference to the engine sensors. The analog power and the analog sensor reference to the engine sensors is switched between the primary ECM and secondary ECM by the relay panel that is mounted on the left side of the engine. When the secondary ECM assumes control of the engine, the sinking driver for the "Backup ECM Active Lamp" is activated. When the sinking driver for the "Backup ECM Active Lamp" is activated, the reference relay and the 5 V power relay in the relay panel are energized. When the reference relay and the 5 V power relay are energized, the analog power and the analog sensor reference to the engine sensors are switched from the primary ECM to the secondary ECM.

The supply voltage is routed to terminal A of each sensor connector. The analog sensor reference is routed to terminal B of each sensor connector. The sensor signal is routed to terminal C of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Illustration 1	g01626199
Typical schematic 5 V supply

The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the following sensors:

• Left exhaust temperature sensor

• Right exhaust temperature sensor

Both the primary ECM and the secondary ECM can provide digital power and digital sensor reference to the engine sensors. In normal operation, the primary ECM has control of the engine. The primary ECM will provide the digital power and the digital sensor reference to the engine sensors. If the secondary ECM must take over control of the engine, the secondary ECM will provide digital power and the digital sensor reference to the engine sensors.

The power to the engine sensors is switched between the primary ECM and secondary ECM by the relay panel that is mounted on the left side of the engine. When the secondary ECM assumes control of the engine, the sinking driver for the "Backup ECM Active Lamp" is activated. When the sinking driver for the "Backup ECM Active Lamp" is activated, the 8 V power relay in the relay panel is energized. When the 8 V power relay is energized, the digital power to the engine sensors is switched from the primary ECM to the secondary ECM.

The digital sensor reference to the engine sensors is switched between the primary ECM and secondary ECM by the "RSR" relay that is mounted in the control panel. When the secondary ECM assumes control of the engine, the sinking driver for the "Backup ECM Active Lamp" is activated. When the sinking driver for the "Backup ECM Active Lamp" is activated, the "RSR" relay in the control panel is energized. When the "RSR" relay is energized, the digital digital sensor reference to the engine sensors is switched from the primary ECM to the secondary ECM.

The supply voltage for the sensors is routed from the ECM to terminal A of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal B of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If the diagnostic code 262-3 or the diagnostic code 263-3 is logged, it is possible that all of the sensors have been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has failed.

Illustration 2	g01627272
Typical schematic 8 V supply

Illustration 3	g01628953
P1 ECM connector (P1-2) "5 V sensor supply" (P1-3) "Analog sensor reference" (P1-4) "8 V digital sensor supply" (P1-5) "Digital sensor reference" (P1-55) +Battery (secondary ECM) (P1-57) +Battery (primary ECM)

Illustration 4	g01628974
P2 ECM connector (P2-29) "Backup ECM Active Lamp"

Illustration 5	g01327616
Terminal locations for the A-C1/E-C2/E-C1 Right hand cross over harness (Terminal A) "Analog sensor reference" (Terminal B) "5 V sensor supply" (Terminal C) "8 V digital sensor supply" (Terminal D) "Digital sensor reference"

Illustration 6	g01629816
Terminal locations for the following connectors A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel and C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel (Terminal 10) "Backup ECM Active Lamp" (Terminal 34) "Digital sensor reference (LH exhaust temperature sensor)" (Terminal 35) "Digital sensor reference (RH exhaust temperature sensor)" (Terminal 36) "Digital sensor reference (Primary ECM)" (Terminal 40) "Digital sensor reference (Secondary ECM)" (Terminal 41) +Battery

Illustration 7	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

Illustration 8	g01234146
Location of ECM connectors

Illustration 9	g01094844
Sensor connector (Pin A) Sensor supply (Pin B) Sensor return (Pin C) Signal

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove electrical power from the ECM.

2. Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.

   Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

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

4. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Check the harness and wiring for abrasion and for pinch points from the sensors back 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 harness and connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem with 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.

  Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore electrical power to the ECM.

3. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Look for the following diagnostic codes:

   • 262-3

   • 262-4

   • 263-3

   • 263-4

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic code is active.

  Repair: The problem is no longer present. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - Either the 262-3 or 262-4 diagnostic code is active at this time. Proceed to Test Step 3.

• Not OK - Either the 263-3 or 263-4 diagnostic code is active at this time. Proceed to Test Step 5.

Test Step 3. Disconnect the 5 Volt Sensors while you Monitor the Active Diagnostic Codes

1. Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 Volt sensor at the sensor connector. Check for an active 262-3 code or an active 262-4 code.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

   1. Disconnect the following sensors one at a time:

      • Aftercooler temperature sensor

      • Atmospheric pressure sensor

      • Coolant pressure sensor

      • Coolant temperature sensor

      • Crankcase pressure sensor

      • Filtered engine oil pressure sensor

      • Filtered fuel pressure sensor

      • Turbocharger outlet pressure sensor

      • Left turbocharger inlet pressure sensor

      • Right turbocharger inlet pressure sensor

      • Unfiltered engine oil pressure sensor

      • Unfiltered fuel pressure sensor

2. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The 262-3 or 262-4 diagnostic code deactivates when a particular sensor is disconnected.

  Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect all of the connectors. Verify that the problem is resolved.

  STOP

• Not OK - The 262-3 or 262-4 diagnostic code remains active after all of the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Proceed to Test Step 4.

Test Step 4. Check the 5 Volt Supply Voltage at the ECM

1. Remove electrical power from the ECM.

2. Disconnect the J1/P1 ECM connector.

3. Fabricate a wire jumper that is long enough to be used to measure the supply voltage at the ECM connector. Crimp a connector socket to one end of the wire.

4. Remove the supply wire from P1-2. Install the wire jumper into the socket P1-2.

5. Connect the J1/P1 ECM connector.

6. Restore electrical power to the ECM.

7. Measure the voltage between the wire jumper in terminal P1-2 and engine ground.

8. Remove electrical power from the ECM.

9. Remove the wire jumper and replace all wires.

Expected Result:

The voltage measurement is 5.0 ± 0.2 VDC.

Results:

• OK - The voltage measurement is 5.0 ± 0.2 VDC. The ECM is operating correctly.

  Repair: The supply wire is shorted to another wire in the harness or the supply wire is shorted to engine ground. Repair the supply wire.

  STOP

• Not OK - The voltage measurement is not 5.0 ± 0.2 VDC.

  Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP

Test Step 5. Disconnect the 8 Volt Sensors while you Monitor the Active Diagnostic Codes

1. Monitor the active diagnostic code screen on Cat ET while you disconnect each 8 Volt sensor at the sensor connector. Check for an active 263-3 code or an active 263-4 code.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

   1. Disconnect the following sensors one at a time:

      • Exhaust temperature sensor (LH)

      • Exhaust temperature sensor (RH)

2. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The 263-3 or 263-4 diagnostic code deactivates when a particular sensor is disconnected.

  Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect all of the connectors. Verify that the problem is resolved.

  STOP

• Not OK - The 263-3 or 263-4 diagnostic code remains active after the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Proceed to Test Step 6.

Test Step 6. Check the 8 Volt Supply Voltage at the ECM

1. Disconnect the J1/P1 ECM connector.

2. Fabricate a wire jumper that is long enough to be used to measure the supply voltage at the ECM connector. Crimp a connector socket to one end of the wire.

3. Remove the wire from terminal location P1-4 (8 V sensor supply). Install a wire jumper into the socket P1-4.

4. Connect the J1/P1 ECM connector.

5. Restore electrical power to the engine ECM.

6. Measure the voltage between the wire jumper in P1-4 (8 V sensor supply) and engine ground.

7. Remove electrical power from the ECM.

8. Remove the wire jumper and replace all wires.

Expected Result:

The voltage measurement is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage measurement is 8.0 ± 0.4 VDC. The ECM is operating correctly.

  Repair: The supply wire is shorted to another wire in the harness or the supply wire is shorted to engine ground. Repair the supply wire.

  STOP

• Not OK - The voltage measurement is not 8.0 ± 0.4 VDC.

  Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP