In N43/N53 series engines, pressure sensors are used to measure, for example, low-pressure and high-pressure of fuel, oil pressure.
Common features of these sensors:
- electronic hub, which “prepares” data for DME, is embedded in them;
- type of output signal: analogue (0 .. 5 V);
- sensor connection: 3 pin.
Via 3 pins following things are connected:
- +5 V power supply;
- signal (sensor output).
Here, how looks the oil pressure sensor. A module of electronics is marked with a red circle.
And now – description of one unpleasant situation.
Patient: E90, N43 series engine. During the time, the error message regarding oil pressure (static) 30C1 has been recorded more and more often in the DME error message memory.
In the attributes of the error message can be seen – for the warm engine (85 .. 95 oC) by around 2000 .. 3000 RPM required oil pressure was around 4000 hPa but maintained dropped below 2000 hPa!
I tested oil pressure.
Test unit ../F6/F2/F2 indicated correct oil pressure value both in idle and driving. Oil pressure management valve PWM indicated incorrect value ../F6/F2/F3. PWM of the valve was around 20 .. 25 % (correct value: 40 .. 60 %), which means – the valve was almost closed! In turn, almost closed valve means – either oil pump has lowered flow-rate, or there are problems with oil pressure, or – the oil consumpton (flow-rate) is increased.
Oil pressure diagnostic module ../F9/F9 didn’t indicate any problems – oil pressure was maintained correctly.
I checked the oil pressure in emergency mode. For this reason:
- disconnected oil pressure sensor for several seconds (the engine will switch to emergency mode – with max possible oil pressure);
- connected the sensor back, to see the indications of oil pressure indications.
Oil pressure sensor indicated around 2000 hPa (low) pressure, although in this mode it should be 4000 .. 4500 hPa! No doubt left – the car has serious troubles with oil pressure! The oil and oil filter were replaced – the situation didn’t change. PWM of the pressure regulating valve stayed around 20 .. 30 %.
All symptoms indicated mechanical problems. At that moment no manometer to check oil pressure was available (additionally, it would be quite complicated to use it while driving), so it was decided to check the wear of joints of oil pump and crankshaft.
The condition of joints – good.
Also, the oil pump was in perfect technical condition. Regulating valve also was cleaned, preventive maintenance was performed.
Problems with oil pressure didn’t disappear. The culprit of the problem was discovered, repeatedly checking pump pressure in idle, in emergency mode. Suddenly the oil pressure reached even 8500 .. 9000 hPa! It’s clear – the oil pump is not able to maintain such pressure in current mode, obviously – oil pressure sensor sends incorrect data!
Typical PWM value of the valve before replacement of sensor (idle).
Here, idle, emergency mode – after replacing the valve. Pressure, maintained by oil pump: 4000 hPa (for INPA/ISTA indications for this parameter we have to add 1000 hPa!).
PWM value of the valve after replacing the valve (45 .. 55 %).
After replacing the sensor, the error message 30C1 haven’t appeared anymore.
Yes, unfortunately, these pressure sensors can lie. Additionally, the defects can hide very cunning! Good news – such oil pressure sensor costs only around 40 .. 50 EUR. Accordingly – if we have no options (with manometer) to be sure of the correct performance of sensor – I would suggest replacing the sensor even in the case if you have only suspicions relating its performance.
Also, fuel pressure sensors can lie. In my practice I haven’t seen a sensor, which would be completely damaged, but a culprit of increased pressure jittering – yes. This defect is not very common, but unpleasant. Due to the sensor, which data are “jittering”, you can replace many food hubs: LPFP, HPFP, etc.
By the way, such a set of tools:
- manometer (up to 400 bar) for fuel (high-pressure) measurements, with accesories;
- manometer (up to 10 bar) for fuel (low-pressure) measurements, with accesories (can be used for oil pressure measurements too);
the repair specialist managed to provide in time of 2 hours (most part of time took the road to the shop), costs around 100 EUR. I believe it’s a very good investment if you repair BMW in everyday or holiday mode.
One more unpleasant nuance, which is associated with the identification of oil pressure problems:
- in oil pressure test block ../F6/F2/F2;
- in oil pressure diagnostics module ../F9/F9,
NO data of PWM of the pressure regulating valve are visible. In turn, in pressure regulation valve PWM data menu ../F6/F2/F3 no data of required and maintained oil pressure are visible. This nuance gives significant troubles to detect hidden defects – detection of incorrect PWM values is not possible!
And unpleasant nuances, which are associated with HPFP – in no menu no HPFP overpressure valve PWM data are available! Availability of these data would make it easier to evaluate “health” of HPFP, its pressure regulation valve and in, for example, a moment of start would allow evaluating flow-rate of the pump. To make a situation even more complicated – no data of HPFP required pressure are available in any location.