P0234

DTC P0234

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor

DTC P0234
- Turbocharger Engine Overboost

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, ambient 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 these changes into electrical resistance. The engine control module (ECM) supplies a regulated 5 volts on the 5-volt reference circuit and a ground on a low reference circuit. The MAP sensor provides a signal voltage to the ECM, relative to boost pressures, on the MAP 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 295 kPa (42.7 psi) when pressures are high, depending on the BARO. The MAP pressure sensor has a range of 43-365 kPa (6-53 psi). The ECM diagnoses boost pressures 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

* DTCs P0106, P0563, P2564 or P2565 are 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 ECM detects that the measured boost pressure is greater than 39 kPa above the expected range for 10 seconds.

Action Taken When the DTC Sets

* DTC P0234 is a Type A DTC.
* The ECM commands the Engine control system to operate in Reduced Engine Power Mode.
* A message center or an indicator may display Reduced Engine Power.
* Regeneration is inhibited.

Conditions for Clearing the DTC

DTC P0234 is a Type A DTC.

Circuit/System Verification

1. Verify that the following DTCs are not set, P0106, P0107, P0108, or P2563.

^ If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

2. Engine running at idle; observe the scan tool MAP and BARO parameters. The reading should be within 1-10 kPa of each other.
3. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Verify the integrity of the air induction system and the turbocharger system by inspecting for restrictions or leaks.
2. Engine running, command the TC Vane Pos. Ctrl. Solenoid ON, while performing a snapshot of the induction data list. Perform the following actions during the snapshot: Refer to Scan Tool Snapshot Procedure. Component Tests and General Diagnostics

1. Slowly increase the engine speed to 1,700 RPM for 5 seconds, and then slowly return the engine speed to a stable idle.
2. Plot the snapshot and verify that the MAP sensor parameter increases smoothly and follows the Engine Speed parameter through-out the entire engine speed range.

^ If the MAP parameter did not change smoothly or did not follow the Engine Speed parameter, inspect the turbocharger and turbocharger ducts for debris, damage, or sticking vanes. Refer to Turbocharger Cleaning and Inspection. Overhaul

3. If the turbocharger inspections are normal, replace the MAP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Manifold Absolute Pressure Sensor Replacement
* Turbocharger Replacement