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Below is the complete factory procedure to diagnose this code. There are various reasons it will set, but the most common is a faulty boost pressure sensor or a leak in the charge plumbing. Often someone has worked on the engine and left clamps loose or not completely reinstalled the ducts. The best method to check leaks is with the use of smoke machine. Also check the vacuum hoses, which deteriorate and cause the recirculating flap actuator to become inoperative.
 Charge pressure is too low. [P0237] Charge pressure is too low.
1 Inspect charge air system for leaks Special tool
Leaks can now be located acoustically or made visible by spraying on leak detector spray.Question: Was the test o.k.?No
Fig. legend/ fig.
Possible cause and remedy
**End of test**Yes
**End of test**2 Adaptation M16/7 (Recirculating air flap actuator) Possible cause and remedy
**End of test**3 Check component B28 (Pressure sensor)
3a Check actual value B28 (Pressure sensor) Test prerequisite
Status of relevant actual value:
Question: Is the actual value o.k.?3b Test voltage supply of component B28 (Pressure sensor) Test prerequisite
Question: Is the measured value okay?NoThe measured value is not o.k.Possible cause and remedy
**End of test**3c Test signal voltage of component B28 (Pressure sensor) Figure legend
Question: Are the measured values okay?No
**End of test**4 Check correct assignment of compressor Possible cause and remedy:
Engine version: 1 105/120SW
Engine version: 2 140SW