P0234

DTC P0234

DTC DESCRIPTOR

DTC P0234
Turbocharger Engine Overboost

DIAGNOSTIC FAULT INFORMATION






IMPORTANT:
- Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- If there are any other DTCs set, diagnose those first.

CIRCUIT/SYSTEM DESCRIPTION
The manifold absolute pressure (MAP) sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by turbocharger output, engine speed, accelerator pedal input, air temperature, and barometric pressure (BARO). A diaphragm within the MAP pressure sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates this action into electrical resistance. The MAP pressure sensor wiring includes 3 circuits. The engine control module (ECM) supplies a regulated 5 volts to the sensor on a 5-volt reference circuit. The ECM supplies a ground on a low reference circuit. The MAP pressure sensor provides a signal voltage to the ECM, relative to pressure, on the MAP pressure sensor signal circuit. The ECM converts the signal voltage input to a pressure value. Under normal operation, the lowest pressure that can exist in the intake manifold is equal to the BARO. This occurs when the vehicle is operated at idle or when the ignition is ON while the engine is OFF. The highest manifold pressures occur when the turbocharger output is high. Manifold pressure can range from 58 kPa (8 psi) when pressures are low to more than 240 kPa (34 psi) when pressures are high, depending on the BARO. The MAP pressure sensor has a range of 33-255 kPa (4-36 psi). The ECM diagnoses the MAP sensor by a calculated predicted value at a predetermined engine load and speed. The ECM then compares the predicted value to the sensor actual input.

CONDITIONS FOR RUNNING THE DTC
- DTC P2564 or P2565 is not set.
- The engine speed is between 800-3,600 RPM.
- DTC P0234 runs continuously when the above conditions are met

CONDITIONS FOR SETTING THE DTC
The measured boost pressure is more than 39 kPa above the expected range for 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
If the condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections and Inducing Intermittent Fault Conditions.

CIRCUIT/SYSTEM VERIFICATION
If you cannot duplicate the condition, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

CIRCUIT/SYSTEM TESTING
1. If any other DTCs are set, diagnose those DTCs first.
2. Replace the MAP sensor.


REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Manifold Absolute Pressure (MAP) Sensor Replacement