P0234

P0234-TURBOCHARGER OVERBOOST CONDITION

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The base Turbocharger boost pressure is managed by the mechanical Wastegate. The Wastegate is spring loaded in the closed position. Boost pressure is applied against the spring pressure of the Wastegate to control the speed of the Turbocharger. The Wastegate Solenoid is a Pulse Width Modulated (PWM) solenoid that controls the amount of boost pressure applied against the spring pressure of the Wastegate. The way that this system operates is, boost pressure is supplied to the Wastegate Solenoid through a hose connected to the Turbocharger housing. The Powertrain Control Module (PCM) varies the PWM signal to the Wastegate Solenoid to control the amount of boost pressure applied against the Wastegate. When more boost pressure is needed, the Wastegate Solenoid will direct more of the boost pressure to atmosphere and less against the Wastegate spring.

- When Monitored:
The Turbocharger Overboost monitor is run under the following conditions: (1) The engine is running with Turbocharger Wastegate Valve control active, (2) there are no circuit faults present for the MAP Sensor, Wastegate Solenoid, Turbocharger Surge Valve Solenoid, or Boost Pressure Sensor.

- Set Condition:
The Boost Pressure Sensor actual value minus the desired value is above a calibrated amount. The desired value varies depending on driving conditions. Two trip fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. DTC IS ACTIVE

NOTE: Diagnose and repair any related Turbocharger Solenoid or pressure sensor DTCs before continuing with this test.

NOTE: It may be necessary to test drive the vehicle to get this fault to reset.

1. Start the engine and allow it to reach normal operating temperature.

WARNING:
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

2. With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT DTC diagnostic procedure. Intermittent Condition Test.

2. BOOST PRESSURE SENSOR CIRCUIT INSPECTION

NOTE: Damaged, restricted or poorly connected intake and Turbocharger related tubes may cause this DTC to set.

1. Turn the ignition off.
2. Disconnect the PCM harness connectors.
3. Disconnect the Boost Pressure Pressure Sensor harness connectors.
4. Inspect and test each of the sensor circuits between the sensor connector and PCM C2 harness connector.

NOTE: Test each circuit for high resistance.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. WASTEGATE AND SOLENOID INSPECTION

NOTE: A seized or sticking Wastegate may cause this DTC to set.

1. Inspect the Wastegate Solenoid, linkage and the Wastegate for proper operation. Refer to the appropriate service information.
2. Inspect and test each of the Wastegate Solenoid pressure lines/hoses between the engine, the solenoid and the Wastegate.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.

No

- Repair or replace the Turbocharger.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.