Pressure transducers are used in large numbers for exhaust gas recirculation systems (EGR) and VTG-superchargers (”Variable Turbo Geometry”, turbochargers with variable vanes). Their function is similar to that of a ”Dimmer” in an electrical circuit: From a vacuum and atmospheric pressure a mixed pressure (control pressure) is formed in the Pressure transducer that can be infinitely varied via the pneumatic actuator (”vacuum cell”).
- The pressure transducers is the source of a well audible noise („squawking“).
- The turbocharger does not perform.
- No exhaust gas is returned i.e. increased nitrogen oxide levels in the exhaust gas.
Our analyses indicate that the cause for the malfunction cannot be attributed to a defective pressure transducers. In particular in the case of very stiff connecting hose and those having small cross-sections, the column of air trapped in the connecting hoses between actuator and pressure transducers may oscillate. In certain cases, a resonance may then occur which will prevent the pressure transducers from operating properly.
"The corresponding pressure transducers is not defective. Its operation is only impaired through the resonance of the oscillating column of air in the connecting hose."
- Replace the connection hose with a slightly longer or shorter hose.
- Use a connection hose with a larger inside diameter or lower rigidity.
- Swap over the connections on the connection hose: If fitted, detach an elbow from the “OUT” connection of the pressure transducer and swap it with the connecting piece on the actuator.
- If necessary, attach an additional damper.
01 Pneumatic actuator (pressure sensor, EGR valve)
02 Connecting hose
03 Pressure transducer
04 Electrical connection
05 To vacuum pump
06 Fresh air
Make sure that no hoses are buckled. Prevent the hoses from coming into contact with hot engine parts. In such cases there is the risk of a fire. The work described above must only be done by qualified personnel.
Pressure transducers are electrically monitored on vehicles with OBD systems.
|Possible EOBD fault codes can be|
|P0033 Boost pressure control valve - Circuit malfunction||P0245 Boost pressure control valve A - Signal too low|
|P0034 Boost pressure control valve - Signal too low||P0246 Boost pressure control valve A - Signal too high|
|P0035 Boost pressure control valve - Signal too high||P0247 Boost pressure control valve B - Circuit malfunction|
|P0234 Engine supercharging - Limit exceeded||P0248 Boost pressure control valve B - Range / malfunction|
|P0235 Engine supercharging - Limit not reached||P0249 Boost pressure control valve B - Signal too low|
|P0243 Boost pressure control valve A - Circuit malfunction||P0250 Boost pressure control valve B - Signal too high|
|P0244 Boost pressure control valve A - Range / malfunction|
|Indirect monitoring of the Pressure transducer takes place by monitoring the function of the EGR valve|
|P0400 Exhaust gas recirculation - Flow rate malfunction||P0405 EGR valve - Sensor A - Input signal too low|
|P0401 Exhaust gas recirculation - Insufficient flow rate detected||P0406 EGR valve - Sensor A - Input signal too high|
|P0402 Exhaust gas recirculation - Excessive flow rate detected||P0407 EGR valve - Sensor B - Input signal too low|
|P0403 Exhaust gas recirculation - Circuit malfunction||P0408 EGR valve - Sensor B - Input signal too high|
|P0404 Exhaust gas recirculation - Range / malfunction|