3126B Generator Set Engine Caterpillar

Use this procedure to troubleshoot the system only when there is an active diagnostic code or when a diagnostic code can easily be activated. This procedure covers diagnostic codes for the following sensors:

• Fuel pressure sensor

• Engine oil pressure sensor

• Injection actuation pressure sensor

• Turbocharger outlet pressure sensor

• Atmospheric pressure sensor

• Turbocharger Inlet pressure sensor

Use this procedure for the following diagnostic codes:

• 094-03 Fuel Pressure open/short to +batt

• 094-04 Fuel Pressure short to ground

• 100-03 Engine Oil Pressure open/short to +batt

• 100-04 Engine Oil Pressure short to ground

• 164-03 Injection Acuation Pressure voltage high

• 164-04 Injection Acuation Pressure voltage low

• 273-03 Turbo Outlet Pressure open/short to +batt

• 273-04 Turbo Outlet Pressure short to ground

• 274-03 Atmospheric Pressure open/short to +batt

• 274-04 Atnospheric Pressure short to ground

• 1589-03 Turbo Inlet Air Pressure Sensor open/short to +batt

• 1589-04 Turbo Inlet Air Pressure Sensor short to ground

The troubleshooting procedures for the diagnostic codes of each pressure sensor are identical. The Engine Control Module (ECM) sends a +5 V supply to terminal A for each sensor. The sensor common connection is connected to terminal B of each sensor. The signal voltage from terminal C of each sensor is sent to the J2 ECM connector or the J1 ECM connector.

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect an open in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal wire, the ECM will generate a 03 diagnostic code.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the signal wire and the return wire from the sensor connector to the ECM are good.

If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates an open in the signal wire, an open in the return wire, or a short to ground.

If the sensor is disconnected at the sensor connector and the voltage on the signal wire at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

Illustration 1	g01194096
Schematic for the engine pressure sensors

Illustration 2	g01194099
P1 terminals (P1-2) +5 VDC (P1-3) Return (P1-17) Turbocharger inlet pressure

Illustration 3	g01194101
P2 terminals (P2-2) +5 VDC (P2-3) Return (P2-14) Atmospheric pressure (P2-16) Fuel pressure (P2-24) Engine oil pressure (P2-27) Injection actuation pressure (P2-40) Turbocharger outlet pressure (P2-41) +5 VDC (P2-42) Return

Illustration 4	g01123211
Connectors for the sensors (A) Supply (B) Return (C) Signal

Illustration 5	g01194115
Left side engine view (typical example) (1) Injection actuation pressure sensor (2) Atmospheric pressure sensor (3) Turbocharger outlet pressure sensor (4) Fuel pressure sensor (5) Engine oil pressure sensor

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove electrical power from the ECM.

2. Thoroughly inspect ECM connectors J1/P1 and J2/P2. Also inspect the connectors for pressure sensors. 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 connector and the sensor connectors that are associated with the active diagnostic code.

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

5. Check the harness and wiring for abrasions 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 wiring are OK. Proceed to Test Step 2.

• 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 the Voltage on the +5 V Supply Wire

1. Disconnect the harness connectors for the following sensors:
   • Fuel pressure sensor

   • Engine oil pressure sensor

   • Injection actuation pressure sensor

   • Turbocharger outlet pressure sensor

   • Atmospheric pressure sensor

   • Turbocharger Inlet pressure sensor

2. Restore electrical power to the ECM.

3. Measure the voltage between terminals A (supply) and B (return) at each sensor connector on the engine harness.

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

4. Remove electrical power from the ECM.

5. Reconnect all of the sensors.

Expected Result:

Each voltage measurement is 5.0 ± 0.2 VDC.

Results:

• OK - Each voltage measurement is 5.0 ± 0.2 VDC. Proceed to Test Step 3.

• Not OK - At least one voltage measurement is not 5.0 ± 0.2 VDC.

  Repair: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test".

  STOP

Test Step 3. Check for Active Diagnostic Codes

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

2. Restore electrical power to the ECM.

3. Use Cat ET to check for active diagnostic codes. Wait at least 30 seconds so that any codes may become active. Look for an active diagnostic code for an engine pressure sensor.

4. Determine if the problem is related to a 03 diagnostic code or to a 04 diagnostic code.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic codes are active for the engine pressure sensors.

  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 04 Code - A 04 diagnostic code is active. Proceed to Test Step 4.

• Active 03 code - A 03 diagnostic code is active. Proceed to Test Step 5.

Test Step 4. Disconnect the Suspect Sensor in Order to Create an Open Circuit

1. Remove electrical power from the ECM.

2. Disconnect the harness connector of the sensor with the 04 diagnostic code.

3. Restore electrical power to the ECM.

4. Use Cat ET to check for active diagnostic codes. Wait at least 30 seconds for activation of the diagnostic codes. Check for an active 03 diagnostic code for the disconnected sensor.

5. Remove electrical power from the ECM.

Expected Result:

A 03 diagnostic code is now active for the disconnected sensor.

Results:

• OK - A 04 diagnostic code was active before you disconnected the sensor. A 03 diagnostic code became active after the sensor was disconnected.

  Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - A 04 diagnostic code was active before you disconnected the sensor. The 04 diagnostic code remained after the sensor was disconnected. Leave the sensor disconnected. Proceed to Test Step 6.

Test Step 5. Create a Short at the Connector for the Suspect Sensor

1. Remove electrical power from the ECM.

2. Disconnect the connector for the suspect sensor.

3. Install a jumper wire with Deutsch sockets on each end between terminals B (return) and C (signal) on the harness connector for the suspect sensor.

4. Restore electrical power to the ECM.

Note: Monitor Cat ET for diagnostic codes before installing the jumper wire and after installing the jumper wire.

5. Use Cat ET to check for active diagnostic codes. Wait at least 30 seconds so that any codes may become active. Look for a 04 diagnostic code.

6. Remove the jumper wire.

7. Remove electrical power from the ECM.

Expected Result:

A 03 diagnostic code was active before the jumper wire was installed. A 04 diagnostic code became active when the jumper wire was installed.

Results:

• OK - A 03 diagnostic code was active before the jumper wire was installed. A 04 diagnostic code became active when the jumper wire was installed. The engine harness and the ECM are OK.

  Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the new sensor, permanently install the new sensor. Clear any logged diagnostic codes.Verify that the problem is resolved.

  STOP

• Not OK - A 03 diagnostic code was active before the jumper wire was installed. The 03 diagnostic code remained active when the jumper wire was installed. Proceed to Test Step 6.

Test Step 6. Check the Operation of the ECM

1. Remove electrical power from the engine ECM.

2. Check the operation of the ECM by creating an open at the ECM.

   1. Disconnect the ECM connector for the suspect sensor.

   2. Fabricate a jumper wire that is long enough to reach from a terminal at the ECM connector to the engine ground stud. Crimp a connector socket to one end of the jumper wire.

   3. Remove the signal wire for the suspect sensor from the ECM connector. Install the jumper wire into the terminal location for the signal wire of the suspect sensor.

   4. Connect the ECM connectors.

   5. Restore electrical power to the engine ECM.

   6. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code.

      An open circuit diagnostic code (03) will be active for the suspect sensor.

3. Check the operation of the ECM by creating a short at the ECM.

   1. Short the jumper wire that is installed into the ECM connector to engine ground.

   2. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code.

      A short circuit diagnostic code (04) will be active for the suspect sensor.

   3. Remove electrical power from the engine ECM.

4. Remove the wire jumper. Reconnect all wires and connectors.

Expected Result:

A 03 diagnostic code was active when the signal wire was removed from the ECM connector. A 04 diagnostic code became active when the jumper wire was installed between the wire in the terminal for the suspect sensor and engine ground.

Results:

• OK - The ECM is operating properly. There is a problem in the wiring between the ECM and the sensor connector.

  Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. The problem may be in a connector. Repair the return wire and/or the connector. Replace parts, if necessary.If the code is only active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire and/or the connector. Replace parts, if necessary.Verify that the problem is resolved.

  STOP

• Not OK - One of the following conditions exists: The 03 diagnostic code is not active when the signal wire is disconnected. The 04 diagnostic code is not active when the wire jumper is installed.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP