Each quarter the team of Bimmerprofs receives data regarding hundreds of N43/N53 engines. Several tenths of them are inspected on the spot; regarding others, the INPA data and the outline of the situation and problems from their owners are received.

It’s time to summarize most common defects of these complicated engines and also mark most safe elements.


NOx system

Unfortunately, without surprises. 90 .. 95% of cars has problems with NOx system.

In very rare cases (only 5 .. 10%) only 30EA error message recording is present, and the problem is solved with a desulphation session.

In other cases, when 30EA is recorded, the cause of it is (also) problems with NOx sensor – a hidden defect, as a result of which the NOx sensor periodically don’t reach Active mode.

At least one-half of inspected cars has error message 30E9 recorded, which means – if there wouldn’t be NOXEM, the bill of repairs would reach 2000 .. 3000 EUR.

Other cars have diagnosed with persistent NOx sensor problems (both error messages regarding self-diagnostics and Lambda binary/linear), and the performance of NOx catalytic converter is not measured. In last two cases the installation of NOXEM was recommended because the NOx catalytic converter was obviously damaged (it’s getting damaged also in cases, when/if it’s not cleaned from sulfur for a long time due to defects of NOx sensor).


CO catalytic converters

Damages of CO catalytic converter were found for 5 .. 10% of cars, in some cases even for engines with small mileage (100.000 .. 150.000 km). Here we have to remind, that the damages of CO catalytic converters are typically caused by increased oil consumption. That, in case, is typically caused by defective crankcase ventilation (ruptured membrane).


Crankcase ventilation valve

Quite often found the problem, characteristic for around 15 .. 20% of cars. For some of these cars, the CO catalytic converters were damaged, some had problems with idle, misfires, offset type fuel LTFT.


Fuel supply

Quite often found the problem – problems of the low-pressure system. Unstable low-pressure is characteristic for at least 10 .. 15% of these cars. For some of the cars, the problem was solved by replacing the fuel filter, for some cars the pump’s motor had to be replaced. Here we have to remark typical mistake – many are replacing charcoal filter, which actually is vapor filter for fuel tank, not a fuel filter! The fuel filter is placed in the fuel tank, on the opposite side of the fuel pump. On this moment there are practically no cases with a confirmed defect of HPFP.

Around 5% cars in History or Info lists had error messages regarding rail pressure – lowered rail pressure at the moment, when the engine starts. This error message can be caused by leaking injectors, leaking HPFP valve, but not problems with HPFP itself.


Water pump

A relatively common problem. Most popular error message: 2E85. Unfortunately, the water pump usually has to be replaced, because the repair is difficult (the body becomes fragile due to time impact, the correct opening of it is almost impossible).


Lubrication system

Error messages regarding insufficient oil pressure most often are detected to N43 series engines. It should be noted, that quite often “recently” replaced oil filters looked as if they were not replaced for at least 30’000 km or even more. In practically all cases the problem was solved, replacing oil filter and oil. In very rare cases MSD has performed restart, because it has detected Internal Fehler (for example, communication via SPI data exchange channel – manufacturer’s software error), as a result MSD detected incorrect (increased pressure) readings of oil pressure sensor, for time (till next session) it switches on the emergency oil supply mode (with max possible oil pressure). In such cases – update the SW releases as much as possible. It has to be understood, that this error message is caused by software mistake, not with a defect in the lubrication system.



Several cases – the injector got stuck in opened position. As a result: error messages regarding a defect of high -pressure system (decreased pressure, high fuel consumption); error messages regarding misfire; turning off the damaged cylinder.

Several cases – significant (rapidly increasing) leakage of the injector: mechanical tests of the cylinder (in idle) outside the allowed parameters, as a result – error messages regarding fuel trim to exact cylinder, turned-off individual adaptations of the cylinders, vibration of the engine in idle. Relatively often, for around 5% or the car had problems with spilling injector, manifestations of the damage – increased number of misfires (evaluating with ELM 327). Usually most often change of spark plug of the current cylinder (symptom – the park plug is burned with dark burn) will help.


Ignition coils

A relatively common problem. Thanks to EML 327 adapter, it’s easy to identify the misfiring cylinder. Taking into account specific overvoltage problems, the ignition coil can be damaged very soon after replacement. One more plus – ignition coils are relatively cheap, replacement – very simple. Efficient preventive solution – installation of snubbers.



Not taking in account several typical cases, when MSD self-diagnostics has recorded error messages regarding the inadequacy of VANOS position or camshaft position sensor, there were several cases, when the jittering of some position of the shaft was increased, when driving evenly. Exhaust shaft problems were dominating, but sometimes also jittering of inlet shaft was detected. In all cases, the problem was solved by replacing the current solenoid.


DME defects

Several cases with 30BA or 30BB error messages also were marked – the problem was solved by replacing MOSFET of the ignition coils.

In 3 .. 5% cases the uneven performance of the engine was solved by updating the software.


DISA valves

Relatively common (mechanical) problem for N43 series engines.


Safe components

Wery rare are defects of:

a) air mass measuring sensor;

b) knock sensors;

c) exhaust temperature sensor*;

d) engine temperature sensor.

* defect usually is related to high-voltage spikes from ignition coils or injectors wireset are induced on temperature sensor wires. Special attention to this problem has to be paid if 2EAE error message regarding NOx sensor is recorded repeatedly.


Rare are defects of:

a) Lambda probes;

b) sensors of crankshaft and camshaft;

c) throttle shaft and accelerator pedal;

d) DISA valve(s)/N53;

e) EGR valve;

f) oil presusre and oil level/quality sensor.