C7 and C9 On-Highway Engines Caterpillar

The clean gas induction (CGI) system routes clean gas from the outlet of the Diesel Particulate Filter (DPF) to the inlet of the turbocharger. The CGI system consists of the following components:

• CGI cooler

• Sensor group

• Control group

CGI Cooler

The CGI cooler uses engine coolant to cool the clean gas.

Sensor Group

The sensor group consists of these components:

Venturi - The venturi is a restriction in the duct between the DPF and the turbocharger. Two pressure taps on the venturi provide connection points for tubing.

Tubing - Tubing connects the venturi's pressure taps to two pressure sensors.

Sensors - Three sensors sense the parameters of the clean gas.

The sensor group produces electrical signals that indicate the values of the following parameters:

CGI Temperature - This is the temperature of the clean gas in the duct.

CGI Absolute Pressure - This is the absolute pressure of the clean gas in the duct.

CGI Differential Pressure - This is the pressure drop across the venturi.

Electrical wiring sends the signals from the sensors to the Engine Control Module (ECM). The ECM uses the signals to determine the mass of the clean gas that is flowing into the turbocharger.

The ECM creates a pulse width modulated signal (PWM) that indicates the amount of clean gas that is desired. Wiring sends the PWM signal from the ECM to the control group.

Control Group

The control group consists of the following components:

Coil - The coil receives the PWM signal from the ECM. The coil creates a magnetic field that is detected by the actuator.

Actuator - The actuator uses pressurized engine oil to convert the coil's magnetic field to rotation of a shaft. The shaft is connected to the valve assembly.

Valve Assembly - The valve assembly contains a flapper. The flapper is connected to the actuator's shaft. The flapper moves in order to vary the amount of clean gas that flows into the turbocharger.

During normal engine operation, the ECM commands the flapper to a position that results in the desired flow of clean gas. Illustration 1 shows the flapper in the closed position and in the open position. The ECM can command the flapper to any position between the closed position and the open position.

Illustration 1	g01384096
Sectional view of a typical CGI valve assembly

Illustration 2	g01319012
Component identification on the C7 and C9 engines This is a typical view. The location of control group (4) and (6) and temperature sensor (5) depends on the chassis. (1) Differential pressure sensor (2) Absolute pressure sensor (3) Tubing (4) Valve assembly (5) Temperature sensor (6) Actuator (7) Venturi (8) CGI cooler

Illustration 3	g01319058
Component identification on the C13 and C15 engine (3) Tubing (5) Temperature sensor (7) Venturi (8) CGI cooler

Note: Refer to Troubleshooting, "Sensor Signal (Analog, Active) - Test" for codes that relate to the sensors.

Illustration 4	g03404821
Schematic diagram for the CGI system

Test Step 1. Determine The Code

1. Establish communication between the Caterpillar Electronic Technician (ET) and the engine ECM.

   Note: The communications adapter must be communicating on both data links in order to perform this procedure. Refer to Troubleshooting, "Electronic Service Tools" for additional information, if necessary.

Determine the logged code for the CGI system.

Note: Troubleshoot a -5 code or a -6 code first if more than one code for the CGI system is logged.

Expected Result:

A -5 code is logged.

Results:

• Logged -5 code - The current flow through the circuit for the control group was low. Proceed to Test Step 2.

• Logged -6 code - The current flow through the circuit for the control group was excessive. Proceed to Test Step 4.

• Logged -15 code or -16 code - The CGI flow was excessive. Proceed to Test Step 5.

• Logged -18 code - The CGI flow was low.

  Repair: Perform the following procedure:

  1. Inspect the piping between the outlet of the DPF and the venturi. Look for these problems:
     • Cracks

     • Loose clamps

     • Broken piping

     Make the necessary repairs.

  2. Run the "Air System Verification Test". Verify that the CGI flow is correct during the test.

  STOP

Test Step 2. Check the Wiring for Problems

Carefully follow this procedure in order to identify the root cause of an intermittent wiring problem.

1. Verify that the engine is OFF and that the keyswitch is ON.

2. Inspect the wiring between the P2 connector and the harness connector for the coil. Look for these problems:
   • Loose connectors or damaged connectors

   • Moisture on the connectors or the wiring

   • Damage that is caused by excessive heat

   • Damage that is caused by chafing

   • Improper routing of wiring

   • Damaged insulation

3. Disconnect the connectors for the coil. Carefully inspect the terminals in each connector for proper installation. Each terminal must be clean and dry. Clean the terminals, if necessary.

4. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.

Expected Result:

There is a problem with the wiring.

Results:

• Yes - There is a problem with the wiring.

  Repair: Make the necessary repairs. Then, perform the "Air System Verification Test". Verify that the -5 code does not return.

  STOP

• No - The wiring appears to be OK. Proceed to Test Step 3.

Test Step 3. Check the Wiring for an Open Circuit

1. Connect a jumper wire between the terminals of the harness connector for the coil. This replaces the coil with a short circuit.

2. Clear the logged -5 code.

3. Run the "Air System Verification Test".

Expected Result:

A -5 code is activated during the test.

Results:

• Yes - A -5 code is activated during the test. The ECM did not detect the jumper wire. There is a problem with the wiring between the P2 connector and the harness connector for the coil.

  Repair: Repair the wiring, when possible. Replace parts, if necessary.

  STOP

• No - A -6 is activated during the test. The ECM detected the jumper wire. The wiring is OK.

  Repair: Perform the following procedure:

  1. Remove the jumper wire. Connect the coil to the harness.

  2. Clear the logged -6 code.

  3. Run the "Air System Verification Test".

     Replace the coil if the -5 code is activated during the test.

     Troubleshoot any additional codes if the -5 code is not activated during the test. The original -5 code was caused by a poor electrical connection.

  STOP

Test Step 4. Check the Wiring for a Short Circuit

1. Disconnect the connectors for the coil.

2. Clear the logged -6 code.

3. Run the "Air System Verification Test".

Expected Result:

A -6 code is activated during the test.

Results:

• Yes - A -6 code is activated during the test. There is a problem with the wiring between the P2 connector and the harness connector for the coil.

  Repair: Repair the wiring, when possible. Replace parts, if necessary.

  STOP

• No - A -5 code is activated during the test.

  Repair: Perform the following procedure:

  1. Connect the connectors for the coil.

  2. Clear the logged -5 code.

  3. Run the "Air System Verification Test". Verify that the -6 code is activated during the test.

  4. Replace the coil. Verify that the problem is resolved.

  STOP

Test Step 5. Check for a Code for Low Oil Pressure

Determine if either of the following codes are logged:

• 100-1 Engine Oil Pressure : Low - Most Severe (3)

• 100-17 Engine Oil Pressure : Low - Least Severe (1)

Expected Result:

Neither code is logged.

Results:

• Neither code is logged. - Proceed to Test Step 6.

• A "low oil pressure" code is logged -

  Repair: Perform the following procedure:

  1. Refer to Troubleshooting, "Oil Pressure Is Low". Continue with this procedure after the low oil pressure condition is resolved.

  2. Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP

Test Step 6. Run the "Air System Verification Test"

Run the "Air System Verification Test". Determine if the CGI flow is high.

Expected Result:

The CGI flow is high during the test.

Results:

• Yes - The CGI flow is high during the test. Proceed to Test Step 7.

• No - The CGI flow is within the expected range during the test. Proceed to Test Step 9.

Test Step 7. Check the Operation of the Actuator

1. Run the "Air System Verification Test". Observe the actuator's shaft during the test.

2. Unbolt the actuator from the valve assembly.

Expected Result:

The actuator's shaft does not rotate smoothly during the test.

Results:

• Yes - The actuator's shaft does not rotate smoothly during the test. Proceed to Test Step 8.

• The actuator's shaft rotates smoothly. -

  Repair: Perform the following procedure:

  1. Replace the valve assembly.

  2. Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP

Test Step 8. Check the Oil Pressure at the Actuator

1. Install a tee at both ports of the actuator.

2. Connect an oil pressure gauge to each tee.

3. Start the engine.

4. Observe the pressure readings on the gauges.

Expected Result:

The inlet pressure is significantly less than the engine oil pressure reading on Cat ET. The outlet pressure is less than 35 kPa (5 psi).

Results:

• Yes - The oil pressure at the inlet is significantly less than the oil pressure reading on Cat ET. The outlet pressure is less than 35 kPa (5 psi). The oil line for the inlet is restricted.

  Repair: Perform the following procedure:

  1. Determine the cause of the restricted oil line. Make the necessary repairs.

  2. Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP

• No - The oil pressure at the inlet is approximately equal to the oil pressure reading on Cat ET. The outlet pressure is greater than 35 kPa (5 psi). The oil line for the outlet is restricted.

  Repair: Perform the following procedure:

  1. Determine the cause of the restricted oil line. Make the necessary repairs.

  2. Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP

• No - The oil pressure at the inlet is approximately equal to the oil pressure reading on Cat ET. The outlet pressure is less than 35 kPa (5 psi). The oil lines are OK.

  Repair: Perform the following procedure:

  1. Remove the valve from the actuator.
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  Illustration 5	g01330553
  Valve (9) Inlet screen

  2. Carefully inspect inlet screen (9). Remove any debris from the inlet screen.

  3. Install the valve.

  4. Run the "Air System Verification Test".
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  Illustration 6	g01330555
  Typical valve assembly and actuator (4) Valve assembly (6) Actuator

  5. Replace actuator (6) if the flapper does not rotate smoothly. Replace valve assembly (4) if the flapper rotates smoothly.

  STOP

Test Step 9. Inspect the Hoses for the Sensors

1. Inspect the small rubber hoses near the sensors for the CGI system. Look for cuts or other damage.

Expected Result:

The hoses are OK.

Results:

• Yes - The hoses are not cut or damaged. Proceed to Test Step 10.

• No - A hose is cut or damaged.

  Repair: Replace the damaged parts. Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP

Test Step 10. Inspect the Venturi

Remove the venturi. Inspect the holes on the inside of the venturi.

Expected Result:

The holes are clean.

Results:

• Yes - The holes are clean.

  Repair: Replace actuator (6) and valve assembly (4). Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP

• No - The holes are restricted.

  Repair: Carefully clean the venturi. Replace the venturi, if necessary. Run the "Air System Verification Test". Verify that the CGI flow is within the acceptable range during the test.

  STOP