P0239 – turbocharger boost sensor B circuit malfunction

P0239 – technical description of the OBD-II fault code

Turbocharger Boost Sensor B Circuit Malfunction

What does code P0239 mean?

Code P0239 is a standard OBD-II code that is triggered when the Engine Control Module (ECM) detects a discrepancy between the boost pressure sensor B and manifold pressure sensor (MAP) readings when the engine is running at minimum power and the turbocharger pressure should be zero. .

These codes are common to all makes and models of vehicles, and they indicate problems with the turbocharger boost pressure. However, the exact diagnostic steps may vary depending on the specific vehicle model.

OBD codes do not indicate a specific defect, but help the technician determine the area in which to look for the cause of the problem.

How supercharging (forced induction) improves performance

Turbochargers deliver much more air to the engine than the engine is capable of taking in under normal conditions. An increase in the volume of incoming air, combined with more fuel, contributes to an increase in power.

Typically, a turbocharger can increase engine power by 35 to 50 percent, with the engine specifically designed to handle turbocharging. Standard engine components are not designed to withstand the load generated by this type of forced air injection.

Turbochargers provide a significant increase in power with virtually no impact on fuel economy. They use the exhaust gas flow to trigger the turbo, so you can think of it as extra power at no extra cost. However, they can fail suddenly for various reasons, so if there is a problem with the turbocharger, it is recommended to fix it promptly. With a turbocharged engine, failure of the turbocharger can significantly worsen the situation due to the large volume of compressed air.

It is important to remember that a standard turbocharged engine should not be modified by increasing the boost pressure. The fuel delivery and valve timing curves of most engines do not allow for operation at elevated boost pressure, which can cause serious engine damage.

Note: This DTC is virtually identical to P0235, which is associated with Turbo A.

What are the symptoms of trouble code P0239?

The Check Engine light illuminates when a DTC sets. The turbo module may be disabled by the engine controller, resulting in loss of power during acceleration.

Symptoms of a P0239 code include:

1. The P0239 code indicates a problem in the boost control circuit, possibly accompanied by additional codes associated with certain parts of the circuit.
2. Loss of engine acceleration.
3. Boost pressure measurements may be out of range: less than 9 pounds or more than 14 pounds, which is abnormal.
4. Unusual sounds such as whistling or rattling sounds from the turbocharger or pipes.
5. Possible knock sensor code indicating detonation due to high cylinder head temperature.
6. General loss of engine power.
7. Smoke from the exhaust pipe.
8. Dirty candles.
9. High engine temperature at cruising speed.
10. Hissing sounds from the fan.

The Check Engine will be activated and a code will be written to the ECM when this malfunction occurs, causing the turbocharger to shut off and reduce engine power during acceleration.

Possible reasons

Causes of the P0239 trouble code may include:

1. Open circuit of the turbocharger pressure sensor with internal gain.
2. Damaged turbocharger pressure sensor A connector causing an open circuit.
3. Shorted wiring harness between the boost pressure sensor and the engine control module (ECM).

These factors can cause the boost pressure to be mismanaged, which can be associated with several potential problems, including vacuum leaks, air filter problems, wastegate problems, turbo oil supply problems, damaged turbine blades, oil seal problems, and others. In addition, there may be problems with electrical connections and sensors.

How to diagnose trouble code P0239?

Diagnosing turbo problems usually starts with common options, and using simple tools like a vacuum gauge and dial gauge can be quite effective. Below is the sequence of diagnostic steps:

1. Make sure the engine is running normally, there are no bad spark plugs, and there are no codes related to the knock sensor.
2. With the engine cold, check the tightness of the clamps at the turbine outlet, intercooler and throttle body.
3. Try rocking the turbine on the outlet flange to make sure it is securely attached.
4. Inspect the intake manifold for leaks, including vacuum hoses.
5. Remove the actuator lever from the wastegate and operate the valve manually to identify possible draft problems.
6. Install a vacuum gauge into the void in the intake manifold and check the vacuum with the engine running. At idle, the vacuum should be between 16 and 22 inches. If it is less than 16, this may indicate a faulty catalytic converter.
7. Increase the engine speed to 5000 rpm and release the throttle while observing the boost pressure on the gauge. If the pressure is greater than 19 pounds, the problem may be with the bypass valve. If the gain does not change between 14 and 19 lbs, the cause may be a problem with the turbo itself.
8. Cool the engine and inspect the turbine, remove the exhaust pipe and check the condition of the internal turbine blades for damage, bent or missing blades, and for oil in the turbine.
9. Check the oil lines from the engine block to the turbine center bearing and the return line for leaks.
10. Install a dial indicator on the nose of the output turbine and check the end play of the turbine shaft. If the end play is greater than 0,003 inches, it may indicate a problem with the center bearing.

If the turbo is functioning normally after performing these tests, the next step may be to check the boost sensor and wiring using a volt/ohmmeter. Check the signals between the sensor and the engine control unit. It is important to remember that not all OBD2 codes are interpreted the same by different manufacturers, so you should consult the appropriate manual for exact details.

Diagnostic errors

To prevent misdiagnosis, follow these simple guidelines:

1. Check the boost pressure sensor hose for blockages and kinks.
2. Make sure the electrical connections of the sensor are secure and that there are no leaks or kinks in the pressure hoses.

What repairs will fix the P0239 code?

If the boost sensor is not sending correct pressure data to the ECM:

1. Replace the boost sensor.
2. Check the turbo sensor hoses and connections for kinks or blockages and repair or replace them if necessary.
3. Repair the wiring to the sensor or replace the connection to restore normal operation.

How serious is trouble code P0239?

A short to power in the sensor circuit can cause internal overheating of the ECM, especially if the short circuit voltage is greater than 5 V.

If the ECM overheats, there is a risk that the vehicle will not start and may stall.

What is P0239 Engine Code [Quick Guide]