3412E Petroleum Engine Caterpillar

The Electronic Control Module (ECM) creates a regulated voltage of 5.0 ± 0.2 VDC that is supplied to terminal A of the harness connectors for these sensors:

• Atmospheric pressure

• Auxiliary pressure

• Coolant temperature

• Engine oil pressure

• Engine oil temperature

• Fuel temperature

• Fuel pressure

• Injection actuation pressure

• Inlet air temperature

• Turbocharger outlet pressure

This procedure covers the following diagnostic codes:

• 262-03 5 Volt Sensor DC Power Supply short to +batt

• 262-04 5 Volt Sensor DC Power Supply short to ground

A +5 V diagnostic code is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness. The next likely cause is a problem with a sensor. The least likely cause is a problem with the ECM.

The analog sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.

Note: The analog sensors are not protected from overvoltage. Directly connecting the analog sensor to battery voltage can result in damage.

Illustration 1	g01058417
Schematic

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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the keyswitch to the OFF position.

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Illustration 2	g01135982
(1) Coolant temperature sensor (2) Turbocharger outlet pressure sensor (3) ECM (4) J1/P1 ECM connectors (5) J2/P2 ECM connectors (6) Injection actuation pressure sensor (7) J3 Customer connector (8) Fuel presssure sensor connector (9) Primary engine speed/timing sensor (10) Secondary engine speed/timing sensor (11) Fuel temperature sensor (12) Atmospheric pressure sensor (13) Engine oil pressure sensor (14) Engine oil temperature sensor (15) Injection actuation pressure control valve (IAPCV)

2. Thoroughly inspect connectors (4), (5), and (7). Thoroughly inspect the connectors for each analog sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect".

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Illustration 3	g01136002
P1 terminals that are associated with the analog supply for the engine sensors (P1-36) +5 VDC (P1-30) Return

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Illustration 4	g01139681
J3/P3 terminals that are associated with the analog supply for the engine sensors (14) +5 VDC (15) Return

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Illustration 5	g01123211
Connectors for the sensors (A) Supply (B) Return (C) Signal

3. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the analog sensor supply.

4. Check the torque of the allen head screw on the ECM connectors and the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

5. Check the harness and the wiring for abrasion and for pinch points from each sensor back to the ECM.

Expected Result:

All of the 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 - The connectors and/or wiring need repair.

  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 repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

2. Turn the keyswitch to the ON position.

3. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Look for these codes:
   • 262-03

   • 262-04

Expected Result:

One of the above codes is active.

Results:

• OK - None of the above codes are active.

  Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".If the engine is running properly at this time, there may be an intermittent problem in a harness that is causing the codes to be logged. Refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Active 262-03 code - A 262-03 diagnostic code is active. Proceed to Test Step 3.

• Active 262-04 code - A 262-04 diagnostic code is active. Proceed to Test Step 4.

Test Step 3. Check the Voltage on the Analog Supply Wire

1. Turn the keyswitch to the OFF position.

2. Disconnect the harness connectors for the following sensors:
   • Atmospheric pressure

   • Auxiliary pressure

   • Coolant temperature

   • Engine oil pressure

   • Engine oil temperature

   • Fuel temperature

   • Fuel pressure

   • Injection actuation pressure

   • Inlet air temperature

   • Turbocharger outlet pressure

3. Turn the keyswitch to the ON position.

Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition.

4. Measure the voltage between terminals A and B at each sensor connector on the engine harness.

Expected Result:

Each voltage measurement is 5.0 ± 0.2 VDC.

Results:

• OK - Each voltage measurement is 5.0 ± 0.2 VDC. The sensors are receiving the correct voltage.

  Repair: Connect all of the sensor connectors. Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - At least one voltage measurement is not 5.0 ± 0.2 VDC. There is a problem with the wiring or with the ECM. Proceed to Test Step 5.

Test Step 4. Disconnect the Analog Sensors and Check for Active Diagnostic Codes

1. Disconnect the following sensors one at a time. Wait for 15 seconds after you disconnect each sensor. Check for the active 262-04 diagnostic code again.
   • Atmospheric pressure

   • Auxiliary pressure

   • Coolant temperature

   • Engine oil pressure

   • Engine oil temperature

   • Fuel temperature

   • Fuel pressure

   • Injection actuation pressure

   • Inlet air temperature

   • Turbocharger outlet pressure

Expected Result:

The 262-04 diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The 262-04 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 262-04 diagnostic code remains after all of the sensors are disconnected. Leave the sensors disconnected. Proceed to Test Step 5.

Test Step 5. Check the Analog Supply Wire for a Short

1. Turn the keyswitch to the OFF position.

2. Disconnect the J1/P1 ECM connector.

3. Verify that all of the analog sensors are disconnected.

Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.

4. Measure the resistance between P1-36 analog supply and all of the other terminals on the P1 ECM connector.

5. Measure the resistance between terminal P1-36 and the engine ground.

Expected Result:

Each resistance measurement indicates an open circuit.

Results:

• OK - Each resistance measurement indicates an open circuit. Proceed to Test Step 6.

• Not OK - At least one of the resistance measurements does not indicate an open circuit. A +5 V supply wire has a short circuit. There may be a problem with a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 6. Check the Analog Supply and the Sensor Return for an Open Circuit

1. Install a wire jumper between P1-30 analog supply and P1-36 sensor return.

Note: Wiggle the harness during the following measurements in order to reveal any intermittent short condition.

2. Measure the resistance between terminals A and B at the harness connector for each analog sensor.

Expected Result:

Each resistance measurement is less than ten Ohms.

Results:

• OK - Each measurement is less than ten Ohms. There is no open circuit. Proceed to Test Step 7.

• Not OK - At least one resistance measurement is greater than ten Ohms. The analog supply wire or the return wire has an open circuit. There may be a problem in a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 7. Check the Analog Supply at the ECM

1. Remove P1-30 analog supply from the P1 ECM connector. Install a wire jumper with socket terminals on both ends into P1-30.

2. Connect the J1/P1 ECM connector.

3. Turn the keyswitch to the ON position.

4. Measure the voltage between the wire jumper in P1-30 and the engine ground.

5. Turn the keyswitch to the OFF position.

6. Restore both wires to the original configuration.

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 OK.

  Repair: Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

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

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

  STOP