Problems with oil pressure. How to act?

Problems with oil pressure are widespread for N43 series engines. Very rare, but they also happen for N53 series engines.

What indicates the problems with oil pressure?

  • an appropriate error message, recorded in the DME error message memory (30C1);
  • PWM (../F6/F2/F3) value of an oil hydraulic pressure valve is lowered (<40%).

It other error messages are recorded in the DME error message memory (regarding oil pressure sensor, hydraulic pressure valve), solving of the problems should be started by checking of connections of these parts and replacing them if necessary). I assume that these problems are solved, but the oil pressure is still lowered.

If the engine runs in Emergency mode (with max oil pressure: 6..8 Bar):

  • no error messages in DME error message memory – typically for engines with Bosch engine management system;
  • the error message 30C1 is recorded (and active) for N43/N53 series engines;

there is no slightest doubt that problems to reach the required oil pressure are fundamental.


How to act?
1. Replace the oil and oil filter. It helps for at least one-half of cases.
2. Make sure that the readings of the oil pressure sensor are correct. How to do that? Connect the manometer and compare the pressure indications of the manometer and oil pressure sensor (../F6/F2/F2). If the difference is more than 5 .. 10%, the sensor has to be replaced.
Note: compare the indications by different RPM/required pressure values.

If you don’t have a manometer, you can replace the sensor by prophylactic reasons. It does not cost a lot: 30 .. 50 EUR and quite often turns out to be a culprit of the problem. Besides, sensor problems can be sporadic; it means they can appear and later disappear – it makes it hard to identify the problem of the sensor.
3. Evaluate the freeze-frame of the oil pressure:

  • if the pressure problems are directly for a cold engine, typical cause – clogged oil filter or oil catcher; too thick/inappropriate oil;
  • if the pressure problems are directly after starting the engine (after a long pause), most likely cause – damage of the oil back-valve (it is located in the bottom part of the oil filter body);
  • if the pressure problems are directly for the hot engine, possible causes: increased oil flowrate via bearing shells; increased wear of the oil pump, problems with oil itself (it loses viscosity, for example, if it is diluted with fuel); inappropriate oil is used.

If there are no pronounced regularities, the most popular cause of oil pressure problems: oil hydraulic pressure valve, it tends to clog with oil dirt and also stuck due to wear.

In the image: N43 oil pressure sensor

N43 hydraulic oil pressure valve

P/n of the N43 oil pressure sensor and hydraulic valve


Use only premium quality oil filters and oil, which is required in the specification and one of the well-known brands. Purchase it from reliable suppliers! Replace the oil and filter each 10’000km!

If initial repair works:

  • replacement of oil and oil filter;
  • replacement of oil pressure sensor and hydraulic pressure valve

did not help – unfortunately, the cause of the problem will hide “deeper”. The engine has to be entrusted to an experienced mechanic.


Possible causes of the problem:

  • clogged oil catcher. It tends to clog due to oil dirt, due to, for example, silicone leftover (which is used to seal the engine hubs), also the debris of chain tensioners;
  • wear of the oil pump;
  • an increased flow-rate of the oil contour (typically – due to weared-out bearing shells).

Note: after solving the oil pressure problems, the engine has to be re-adapted!