Diagnostic Trouble Code
P0240
Turbocharger Boost Sensor B Range/Performance
Technical Description P0240
Turbocharger Boost Sensor B Range/Performance
What Does This Mean P0240?
This DTC is a generic powertrain code that applies to all turbocharged or supercharged vehicles.
The power train control module (PCM) both controls and monitors boost pressure, and if measured pressure is greater than commanded pressure, the DTC P0240 will be set and the PCM will turn on the check engine light. In order to diagnose this code, you must have a general understanding of three things:
In a normally aspirated engine (i.e. non-turbo) the downward motion of the pistons, called the intake stroke, creates vacuum in the intake manifold in the same way a syringe draws in fluid. This vacuum is how the air/fuel mixture is drawn into the combustion chamber. A turbocharger is a pump driven by exhaust gasses as they exit the combustion chamber. This creates pressure in the intake manifold. So instead of the engine having to “suck” the air/fuel mixture in, it instead is force fed a greater volume. In essence, there is already compression before the piston begins its compression stroke, as a result increasing compression and therefore increasing power. This is boost pressure.
Boost pressure is controlled by the amount of exhaust gases allowed to pass through the turbo. The greater the amount, the faster the turbo spins, the greater the boost pressure. Exhaust gas is routed around the turbo through a bypass that is known as the waste gate. The PCM controls boost pressure by regulating the opening of the bypass. It does this by opening or closing the waste gate as needed. This is accomplished by means of a vacuum motor mounted on, or near the turbo. The PCM controls the amount of vacuum going to the vacuum motor via 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). The different sensor types account for the different technical description given by each manufacturer but both perform the same function.
This particular code is one that should be addressed as soon as possible due to the increased risk of over boost and catalytic converter damage.
The power train control module (PCM) both controls and monitors boost pressure, and if measured pressure is greater than commanded pressure, the DTC P0240 will be set and the PCM will turn on the check engine light. In order to diagnose this code, you must have a general understanding of three things:
In a normally aspirated engine (i.e. non-turbo) the downward motion of the pistons, called the intake stroke, creates vacuum in the intake manifold in the same way a syringe draws in fluid. This vacuum is how the air/fuel mixture is drawn into the combustion chamber. A turbocharger is a pump driven by exhaust gasses as they exit the combustion chamber. This creates pressure in the intake manifold. So instead of the engine having to “suck” the air/fuel mixture in, it instead is force fed a greater volume. In essence, there is already compression before the piston begins its compression stroke, as a result increasing compression and therefore increasing power. This is boost pressure.
Boost pressure is controlled by the amount of exhaust gases allowed to pass through the turbo. The greater the amount, the faster the turbo spins, the greater the boost pressure. Exhaust gas is routed around the turbo through a bypass that is known as the waste gate. The PCM controls boost pressure by regulating the opening of the bypass. It does this by opening or closing the waste gate as needed. This is accomplished by means of a vacuum motor mounted on, or near the turbo. The PCM controls the amount of vacuum going to the vacuum motor via 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). The different sensor types account for the different technical description given by each manufacturer but both perform the same function.
This particular code is one that should be addressed as soon as possible due to the increased risk of over boost and catalytic converter damage.
Possible Causes P0240
1
Vacuum supply
2
Pinched, collapsed or broken vacuum lines
3
Faulty control solenoid
4
Faulty PCM
Solutions & Repair Steps P0240
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.