Technical Description of OBD-II Trouble Code
The code indicates a range/performance issue with the Turbocharger Boost Sensor B.
What does this mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to all vehicles equipped with turbochargers or superchargers.
The powertrain control module (PCM) is responsible for controlling and monitoring boost pressure. If the measured pressure exceeds the commanded pressure, the PCM will set the DTC P0240 and activate the check engine light. To diagnose this code, it is necessary to have a basic understanding of three key aspects:
In a naturally aspirated engine (non-turbo), the intake stroke creates vacuum in the intake manifold, drawing in the air/fuel mixture. In a turbocharged engine, the turbocharger pumps air into the intake manifold, increasing the pressure and providing a greater volume of air/fuel mixture to the combustion chamber. This increased pressure is known as boost pressure and results in higher compression and power.
Boost pressure is controlled by regulating the amount of exhaust gases passing through the turbocharger. The PCM controls the boost pressure by adjusting the opening of the bypass, known as the waste gate. This is achieved using a vacuum motor and a control solenoid.
The actual pressure in the intake manifold is measured by either a boost pressure sensor (Ford/VW) or a manifold absolute pressure sensor (Chrysler/GM). Although different manufacturers may use different sensor types, they serve the same purpose.
It is important to address this code promptly due to the increased risk of over boost and potential damage to the catalytic converter.
Symptoms
When the conditions for setting the P0240 code are met, the PCM disregards actual manifold pressure readings and uses an inferred or assumed pressure. This leads to limitations in fuel delivery and dynamic injection timing, resulting in reduced engine power.
Causes
Possible causes for this code include:
Diagnostic and Repair Procedures
It is recommended to start by checking for any technical service bulletins (TSBs) related to the specific vehicle. These bulletins may provide known issues and solutions, saving time and money during diagnosis.
