C15 On-highway Engines Caterpillar

This procedure covers the following diagnostic codes:

• 100-3 Oil Pressure voltage high

• 100-4 Oil Pressure voltage low

• 102-3 Boost Pressure voltage high

• 102-4 Boost Pressure voltage low

• 108-3 Barometric Pressure voltage high

• 108-4 Barometric Pressure voltage low

• 385-3 Intake Valve Actuation System Oil Pressure voltage high

• 385-4 Intake Valve Actuation System Oil Pressure voltage low

Background Information

The Engine Control Module (ECM) continuously creates a pull-up voltage on the signal wire for each sensor. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects voltage that is above a threshold on the signal wire, the ECM activates a -3 diagnostic code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a -4 diagnostic code.

Note: There may be a delay of 30 seconds in order for Caterpillar Electronic Technician (ET) to display an active diagnostic code. When you check for a diagnostic code, be sure to wait at least 30 seconds.

The most likely cause of a code is a problem with an electrical connector or wiring. The least likely cause of a code is the ECM.

108-3 Diagnostic Code and High Crankcase Pressure

Some atmospheric pressure sensors that are located in the engine block actually sense crankcase pressure rather than atmospheric pressure. With this type of installation, crankcase pressure of approximately 14 kPa (2 psi) can cause the 108-3 diagnostic code to be generated.

Before you proceed with this test, determine whether the sensor is sensing crankcase pressure or atmospheric pressure.

If the sensor is sensing crankcase pressure, connect Caterpillar Electronic Technician (ET) to the ECM and clear the diagnostic code. Do not start the engine. Maintain electrical power to the ECM. Wait at least 30 seconds for generation of the diagnostic code. Slowly wiggle the wiring for the sensor in an attempt to generate an intermittent code.

If the 108-3 code is generated, continue with the functional test.

If the 108-3 code is not generated, there is either a problem with high crankcase pressure or the code is intermittent, due to a loose connector or damaged wiring.

A plugged crankcase breather will cause excessive crankcase pressure. Leakage of the crankshaft seal can occur. Sealing of the piston rings can be lost. This will enable crankcase blowby to further increase the crankcase pressure.

If the piston rings do not seal, blowby will increase the crankcase pressure and the problem will become worse. Performance will deteriorate. The engine will have poor combustion. Deposits will build up on the pistons, on the valves, and in the cylinder heads. Downward pumping of the pistons against the increased crankcase pressure will further reduce the performance.

Sticking of the pistons will also increase the crankcase pressure. If the problem is not resolved, piston seizure will result. If a problem with a piston is suspected, do not operate the engine. Inspect the cylinder liner for scoring and for scuffing. Replace the piston rings and the cylinder liner, if necessary.

To eliminate crankcase pressure as the cause of the 108-3 diagnostic code, inspect the crankcase breather. If the breather is plugged, clean the breather or replace the breather. Make sure that the air passages for the breather's system are clear.

To verify that the plugged breather was the problem, operate the engine at a high load for at least 30 seconds. If the code does not recur, return the engine to service.

Illustration 1	g01232651
Schematic for engine pressure sensors

Illustration 2	g01103785
Locations of the engine pressure sensors (typical left side engine view) (1) Boost pressure sensor (2) Barometric pressure sensor (3) Engine oil pressure sensor

Illustration 3	g01103786
Typical right side engine view (4) Intake valve actuation pressure sensor

Illustration 4	g01239984
Terminal locations at the P2 ECM connector for the engine pressure sensors (P2-15) Boost pressure (P2-17) Sensor return (P2-28) Engine oil pressure (P2-54) Sensor return (P2-57) Barometric pressure (P2-72) Sensor supply (P2-74) Intake valve actuation pressure (P2-80) Sensor supply

Illustration 5	g01159881
Terminal locations at the sensor connector for the engine pressure sensors (Terminal A) Sensor supply (Terminal B) Sensor return (Terminal C) Signal

Test Step 1. Determine if the Code is Logged or Active

1. Connect Cat ET to the service tool connector.

2. Restore electrical power to the engine ECM.

3. Monitor the active diagnostic code and the logged diagnostic codes on Cat ET.

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

Identify the diagnostic code.

Results:

• Logged code -

  Repair: Do not troubleshoot a logged code unless the code relates to an operator complaint. If the code is logged and the code does not relate to an operator complaint, clear the code.

  If the code is logged and the code relates to an operator complaint, proceed to Test Step 2.

• Active code - Proceed to Test Step 3.

Test Step 2. Check the Integrity of the Connections at the Connectors

1. Turn the keyswitch to the ON position. Do not start the engine.

2. Install a 7X-1708 Multimeter Probe (RED) and a 7X-1709 Multimeter Probe (BLACK) onto the test leads of a multimeter.

3. Check for an intermittent problem at the connector for the suspect sensor:

   Note: Do not disconnect any harness connectors in order to perform this procedure.

   1. Carefully install the spoons (multimeter probes) into the terminal locations for the +5 volt sensor supply and the sensor return at the connector for the suspect sensor.

   2. While you observe the voltage reading on the multimeter, wiggle the wires and pull on the wires at the connector for the suspect sensor.

      The voltage reading will not vary more than 0.5 volts for a solid electrical connection.

   3. Remove the spoons (multimeter probes) from the connector.

4. Check for an intermittent problem at the ECM connector:

   Note: Do not disconnect any harness connectors in order to perform this procedure.

   1. Carefully install the spoons (multimeter probes) into the terminal locations for the +5 volt sensor supply and the sensor return at the P2 ECM connector.

   2. While you observe the voltage reading on the multimeter, wiggle the wires and pull on the wires for the +5 volt sensor supply and the sensor return at the ECM connector.

      The voltage reading will not vary more than 0.5 volts for a solid electrical connection.

   3. Remove the spoons (multimeter probes) from the connector.

5. Turn the keyswitch to the OFF position.

Expected Result:

The voltage reading did not vary more than 0.5 volts during either test.

Results:

• OK - The voltage reading did not vary more than 0.5 volts.

  Repair: The connections are OK at the connectors. There does not appear to be an intermittent problem in the circuit at this time. Return the engine to service.

  STOP

• Not OK - The voltage reading varied more than 0.5 volts during the test.

  Repair: Disconnect the suspect connector and inspect the connector and the terminals for moisture, damage, and corrosion. Repair the connectors and/or the terminals. Return the engine to service.

  STOP

Test Step 3. Check the Supply Voltage at the Sensor Connector

Turn the keyswitch to the ON position. Do not start the engine.

Measure the voltage between terminal A (sensor supply) and terminal B (sensor return) at the harness connector for the sensor that relates to the code.

Expected Result:

The voltage is between 4.5 VDC and 5.5 VDC.

Results:

• OK - The voltage is between 4.5 VDC and 5.5 VDC. The supply voltage is at the sensor connector. Record the voltage measurement. If you are troubleshooting a -3 diagnostic code, proceed to Test Step 4. If you are troubleshooting a -4 diagnostic code, proceed to Test Step 7.

• Not OK - The voltage is less than 4.5 VDC or the voltage is greater than 5.5 VDC.

  Repair: The voltage of the sensor supply is incorrect. Refer to Troubleshooting, "5 Volt Engine Pressure Sensor Supply Circuit - Test".

  STOP

Test Step 4. Check for Battery Voltage on the Signal Wire

Measure the voltage between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code.

Expected Result:

The voltage measurement is less than the +Battery voltage.

Results:

• OK - The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 5.

• Not OK - The voltage measurement is approximately equal to the +Battery voltage. The signal wire is shorted to the +Battery.

  Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 5. Check the Signal Wire for an Open Circuit

1. Disconnect the sensor that relates to the diagnostic code.

2. Connect a jumper wire between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code. This will replace the sensor with a short circuit.

3. Look for a -4 diagnostic code.

Expected Result:

The -3 code does not change to a -4 code when the jumper wire is connected.

Results:

• OK - The -3 code does not change to a -4 code when the jumper wire is connected. Connect the sensor. There is a problem with the wiring harness or with the ECM. Proceed to Test Step 6.

• Not OK - The -3 code changes to a -4 code when the jumper wire is connected. The wiring harness and the ECM are OK.

  Repair: Perform the following procedure:

  1. Remove the jumper wire.

  2. Connect a new sensor to the engine harness. Do not install the sensor into the engine.

  3. Verify that the active -3 diagnostic code does not recur.

  4. Install the sensor into the engine.

  5. Clear all logged diagnostic codes and return the engine to service.

  STOP

Test Step 6. Check the ECM for Proper Operation

1. Determine the P2 signal terminal and the P2 return terminal that relates to the diagnostic code.

2. Remove the signal terminal and the return terminal from the P2 connector.

3. Install a jumper wire into the P2 connector between the signal terminal and the return terminal. This will replace the engine wiring with a short circuit.

4. Look for a -4 diagnostic code.

Expected Result:

A -4 code is active when the jumper wire is installed.

Results:

• OK - A -4 code is active when the jumper wire is installed. The ECM detected the jumper wire at the P2 connector. However, the ECM did not detect the jumper wire at the harness connector for the sensor. There is an open circuit in the wiring.

  Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

• Not OK - A -4 code is not active when the jumper wire is installed. The ECM does not detect the jumper wire at the P2 connector. There is a problem with the ECM.

  Repair: Perform the following procedure:

  1. Restore the P2 wiring to the original configuration.

  2. Temporarily install a test ECM. Refer to Troubleshooting, "Test ECM Mode".

  3. Verify that the problem is resolved.

  4. Install the original ECM and verify that the original problem returns.

  5. If the problem returns with the original ECM, replace the original ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

Test Step 7. Check the Signal Wire for a Short Circuit

1. Disconnect the sensor that applies to the -4 diagnostic code.

2. Look for a -3 diagnostic code.

3. Connect the sensor and look for a -4 diagnostic code.

Expected Result:

When the sensor is disconnected, the -4 code remains.

Results:

• OK - When the sensor is disconnected, the -4 code remains. There is a problem with the wiring harness or with the ECM. Proceed to Test Step 8.

• Not OK - When the sensor is disconnected, the -4 code changes to a -3 code. The harness and the ECM are OK. There is a problem with the sensor.

  Repair: Perform the following procedure:

  1. Connect a new sensor to the engine harness. Do not install the sensor into the engine.

  2. Verify that the active -4 diagnostic code does not recur.

  3. Install the sensor into the engine.

  4. Clear all logged diagnostic codes and return the engine to service.

  STOP

Test Step 8. Check the ECM for Proper Operation

1. Determine the P2 signal terminal that relates to the diagnostic code.

2. Remove the signal terminal from the P2 connector.

3. Check if the -4 diagnostic code becomes an active -3 active code.

Expected Result:

A -3 code is active when the signal wire is disconnected from the P2 connector.

Results:

• OK - A -3 code is active when the signal wire is disconnected from the P2 connector. The ECM detected the open circuit at the P2 connector. However, the ECM did not detect the open circuit at the harness connector for the sensor. There is a problem with the wiring between the P2 connector and the harness connector for the sensor. There may be a problem with a connector.

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

  STOP

• NOt OK - A -3 code is not active when the signal wire is disconnected from the P2 connector. The ECM did not detect the open circuit at the P2 connector. There is a problem with the ECM.

  Repair: Perform the following procedure:

  1. Restore the P2 wiring to the original configuration.

  2. Temporarily install a test ECM. Refer to Troubleshooting, "Test ECM Mode".

  3. Verify that the problem is resolved.

  4. Install the original ECM and verify that the original problem returns.

  5. If the problem returns with the original ECM, replace the original ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP