Several days ago I received a call for help from the owner of N53B30 U0 engine. Car:  E90 LCI, 325i. Sometimes a vibration is observed, loss of power by higher RPM. But, judging by the description, nothing tragical.


And then I saw live data…

Here, a total crash in the 2-nd bank. DME increased fuel mixture for 30%, but instead of rich mixture confirmation, Lambda is 2.9? Totally inadequate data of Lambda probe.

But there is one problem – the Lambda probe has been replaced just now, but the situation has not got better.

Here, the error message:

Interesting situation – there are no error messages regarding the wideband Lambda probe (at least for trim).

There is also no error messages regarding NOx system, although it doesn’t show any sign of life. Even more, for example, menu of NOx catalytic converter:

We see the sulphation of NOx catalytic converter is not being calculated (poisoning 0 mg), in the same time sulphation temperature indicates directly opposite – the time for sulphation session was already a long, long time ago (at least 50’000 km ago).

In addition, MSD, not taking into account a complete crash in the 2-nd bank,

has initiated chemical tests of the injectors (although they have failed). This is in complete contradiction with the basic performance logic of MSD!


Here, the engine is not even been able to create basic adaptations for Stratified charge (obviously, it has never worked in this mode), also individual adaptations of cylinders – not completed.


Here – the opening times of injectors. DME has increased the opening time of injectors for the 2-and bank for almost 2 times! In the same time – it “doesn’t understand”, that actually the probe is “lying” and the mixture is not lean!

To make the situation more interesting, I will add, that recently the injectors, ignition coils an spark plugs were replaced! Without results.

So – the engine injects a double dose of fuel in cylinders No.4, 5 and 6, in addition – DME “don’t understand” this problem, replacement of probes and injectors didn’t help. Taking into account, that the owner of the car drives with such DME for a longer time, CO catalytic converter (of the 2-nd bank) is damaged for sure – I have no illusion.


And here – diagnostic report:

As you can see, all values regarding fuel mixture, NOx system, injectors data are marked as ”F” or ”failed”.


What happened to this engine?

Some time ago, when problems with NOx system (sensor) started, the owner of the car (possibly – even previous owner) decided not to solve problems with NOx system, but – “upgrade” the DME software. I have seen several hundred versions, in which the NOx system is “disconnected”, using NCS.  Consequences – a vibrating engine, with typical misfires, increased fuel consumption, difficult cold starts – everyday problems. Here the “specialist” got to the case more seriously.

After a moment, when DME started to record the error messages regarding the performance of CO catalytic converters (a regular defect after such manipulations – CO catalytic converters are overloaded because the fuel mixture of cylinders is incorrect, trim of Lambda probes – incorrect, in addition – misfires), DME “improvers” decided to “solve” problem, disconnecting the control probes. This time not the heating of probes is disconnected (probes have been taken out of configuration of DME), what is a typical way, but the data processing of probes has been disconnected.

These operations led to visible consequences – DME trimmed the wideband probe completely incorrectly and works with the inappropriate fuel mixture.

The engine shivers, continuous misfires in cylinders No.4, 5 and 6.


What is the summary of the story?

Instead of expenses of several hundreds of EUR, the owner of the car has chosen a slightly “cheaper” solution.

To this moment:

  • injectors, ignition coils, spark plugs, Lambda probe are replaced – the bill around EUR 3000.
  • The NOx catalytic converter is damaged (it costs above EUR 2000).
  • The CO catalytic converter od 2-and bank is damaged (price of OEM CO catalytic converter – more above EUR 2000).
  • The software of DME has to be restored, configuration/encoding. Costs – several hundreds of EUR; if there will be no specialist in the area, who will be able to do that, the official solution: new DME, costs around EUR 1500.
  • And finally – the question regarding the NOx sensor has to be solved. Here the costs are EUR 350 .. 550.
  • Some more EUR 500 .. 1000 will go for expenses for work and service procedures.

It’s not hard to calculate – to restore the normal performance of the engine, total expenses will reach around EUR 10’000.

Unfortunately, this is a typical result, when the “chip tuners” get to modify the engine management unit.