3412E Engine for Caterpillar Built Machines 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 ECM supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

• Engine oil pressure sensor

• Atmospheric pressure sensor

• Injection actuation pressure sensor

• Intake manifold pressure sensor

• Engine coolant temperature sensor

• Engine oil temperature sensor

• Fuel temperature sensor

The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the throttle position sensor.

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 any of the -3 diagnostic codes are active, it is possible that a sensor has been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has failed.

Illustration 1	g01395313
Typical schematic

Illustration 2	g01408229
Component location (1) Coolant temperature sensor (2) Turbocharger outlet pressure sensor (3) Injection actuation pressure sensor (4) Fuel temperature sensor (5) Atmospheric pressure sensor (6) Engine oil pressure sensor (7) Engine oil temperature sensor

Test Step 1. Inspect Electrical Connectors and Wiring

1. Remove electrical power from the ECM.

Show/hide table



Illustration 3	g01408242
ECM (8) J1/P1 connectors (9) J2/P2 connectors

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.

Show/hide table



Illustration 4	g01395441
P1 ECM connector (P1-36) + 5 V sensor supply (P1-30) Sensor return (P1-35) + 8 V digital supply (P1-29) Digital return

Show/hide table



Illustration 5	g01159881
Sensor connector (A) +5 V or +8 V sensor supply (B) Sensor return (C) Signal

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 - A 262-3 or 262-4 diagnostic code is active at this time. Proceed to Test Step 3.

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

Test Step 3. Disconnect the 5 Volt Sensor(s) while you Monitor the Active Diagnostic Codes

1. Use this procedure for any 262 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.

   2. Disconnect the following sensors one at a time:
      • Injection actuation pressure sensor

      • Engine oil pressure sensor

      • Atmospheric pressure sensor

      • Turbocharger outlet pressure sensor

      • Engine coolant temperature

      • Fuel temperature

      • Engine oil temperature

2. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The diagnostic code deactivates when a particular sensor is disconnected.

  Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect the connector(s). Verify that the problem is resolved.

  STOP

• Not OK - The diagnostic code remains active after a sensor is disconnected. Leave the sensor disconnected. The sensor is not the cause of the diagnostic code. Proceed to Test Step 4.

Test Step 4. Check the +5 V Supply Voltages at the ECM

1. Use this procedure for any 262 diagnostic codes.

   1. Disconnect the J1/P1 ECM connector.

   2. Fabricate jumper wires that are long enough to be used to measure the supply voltages at the ECM connector. Crimp connector sockets to one end of each jumper wire.

   3. Remove the wires from terminal locations P1-36 (+5 V sensor supply) and P1-30 (sensor return). Install a jumper wire into each of these terminal locations.

   4. Connect the J2/P2 ECM connector.

   5. Restore electrical power to the ECM.

   6. Measure the voltage between the jumper wire in P1-36 (+5 V sensor supply) and the jumper wire in P1-30 (sensor return).

   7. Remove electrical power from the ECM.

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: There is a problem with the harness. Repair the harness or replace the harness.

  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 V Sensor while you Monitor the Active Diagnostic Codes

1. Use this procedure for any 263 diagnostic codes.

2. Monitor the active diagnostic code screen on Cat ET while you disconnect the throttle position 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.

3. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when the throttle position sensor is disconnected.

Results:

• OK - The 263-3 or 263-4 diagnostic code deactivates when the throttle position 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 throttle position sensor is disconnected. Leave the sensor disconnected. The sensor is not the cause of the diagnostic code. Proceed to Test Step 6.

Test Step 6. Check the +8 V Supply Voltage at the ECM

1. Use this procedure for any 263 diagnostic codes.

2. Disconnect the J1/P1 ECM connector.

3. Fabricate two jumper wires that are long enough to be used to measure the supply voltage at the ECM connectors. Crimp connector sockets to one end of each jumper wire.

4. Remove the wires from terminal locations P1-35 (+8 V sensor supply) and P1-29 (sensor return). Install a jumper wire into each of these terminal locations.

5. Connect the J1/P1 ECM connector.

6. Restore electrical power to the ECM.

7. Measure the voltage between the jumper wire in P1-35 (+8 V sensor supply) and P1-29 (sensor return).

8. Remove electrical power from the ECM. Replace all wires and connectors to the original configuration.

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: There is a problem with the harness. Repair the harness or replace the harness.

  STOP

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

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

  STOP