The area of car servicing is a perfect business! Why? I will start with two examples.
If the area of the product or service is straightforward and is understandable to everyone, it is hard to cheat. For example, if you are buying a cake in the shop – unlike there will be, for example, sand instead of cream, or you can be told that 100 eggs were used to make this cake and because of it the price is ten times higher.
If the industry is very complicated, there also will be very complicated to cheat. I doubt that in the SpaceX company of Elon Musk, some engineers can add the sunflower oil to the rocket fuel just to “test”. Or replace all spare parts of the rocket one after another, because they have no clue where the problem is. Education and also experience is required to work in this company.
The car servicing, instead, can be done by everyone, who desired to do that! And, the best part – the customer usually doesn’t understand a thing! You can replace one part after another – the customer will pay! Even more – if you replace the wrong part and don’t reach any result, most part of the customers will come back to replace some other parts. And you will earn money again – both selling the spare parts and receiving cash for replacement work. Perfect!
Have you ever heard that the service has repaid costs of the wrong diagnostics and unjustified repair works? I don’t know even one case. At the same time, when diagnosing the engine problems, average services fail more than “hit”.


Today’s example: E60, 523i, N53B25.
Several years ago, the problems with the NOx system appeared. Instead of repairing the system properly, it was “switched off” – it was recommended by local “specialists” as a perfect solution.
After moment problems with uneven performance, misfires, vibration, shivering appeared.

  • the LP sensor was replaced. Without success.
  • The HP sensor was replaced. Without success.
  • The LPFP was restored. No changes.
  • Injectors of cylinders No. 1 and No.6 were replaced because their spark plugs were black. Without upgrades.
  • New spark plugs were installed. Bosch.

The car continues to vibrate; misfires can be felt very well, hen the engine is cold, it runs on 4 or 5 cylinders. No success. Now the service “specialists” recommended replacing the HPFP.

So, the customer visited the service for at least 6 .. 7 times, the service performed “diagnostics”, which, of course, was not free-of-charge. Then they performed the “repair”. Then the car (unrepaired, with the same symptoms as before the repair) was returned to the customer. Of course, after paying the bill.

At this moment the patience of the owner of the car ended. When he found out, that even the inappropriate spark plugs were installed, he finally decided to look for another service.
Did the existing service had the appropriate diagnostics equipment? No. Did they had at least basic knowledge of these cars/DME? No. In this case, the meaningless “repair” ended with unjustifiedly spent around EUR 1000. But – the additional costs are just to come, “turning back” the NOx system, solving its problems and other defects.


The “turning off” of the NOx system has deserved a separate section. This time this manipulation was done so inexperiencedly, that it’s a wonder, that DME still functions:

  • Wonder why DME does not maintain the Info error message list;
  • In the History error message list, the error messages appear without attributes. So – the error messages are as if deleted from the error message map, but this deleting has failed;
  • learnbits indicate, that (despite the fact that Stratified charge is not used at all) DME has “stuck” in the creation of individual adaptations of cylinders in Stratified charge mode. Complete crash of the algorithm.

And now let’s see, what is the situation with the injectors, their “health”.
Here, the data of the Rough run in idle. The engine shivers noticeably, and it is also indicated in diagnostics.

There are problems with cylinders No.1! The injector of it leaks! How so? It was just recently replaced!
And yes, as you see, the fuel mixture of the 2-nd bank is enriched. In both banks – incorrect fuel proportion between cylinders – fastest way, how to damage the CO catalytic converters!

Here. The results of the chemical tests of the injectors. For cold engine – the injector of cylinder No.6 was leaking! But – it also is replaced recently!

Here, the live data of injectors. The correction of the flow rate of the injector for cylinder No.6 regularly is so close to the maximum of the allowed corridor, that it is clear that the error message regarding this injector will be recorded very soon. Is the injector clogged? But at the same time – leaking when cold?

Both replaced injectors – damaged? Of course, not. This is a 100% proof that the replacement of the injectors of these cylinders is unjustified. The same cylinders have problems also with new injectors. Around EUR 700 spent completely useless!

Here, the error message lists – the error messages regarding HPFP pressure and pressure data are recorded. Both pressure sensors (also Rail pressure sensor) are replaced! Should they be replaced again? Also, such an option was mentioned in the offer of the previous service.

HPFP data indicate that HPFP works in a full functionality mode (despite the error message 29F2). Obviously, the DME has detected the pump has no troubles to maintain the pressure of 200 Bar. A quick test of the pump confirms – even in case of large flowrates, it has no problems.


What happened to this car?
Very succinctly: these DI engines use piezo injectors. The injectors are very high-speed, but at the same time, they have a very wide scattering of the parameters. DME regularly measures the parameters of the injectors to compensate for this scattering. But, the largest part of these measurements can be performed only in Stratified charge injection mode. If the NOx system has any problems (or it is “turned off”), DME does not use a Stratified charge. Accordingly: no measurements – no injector data. If there is no injector data, there is no option to compensate for the difference in their parameters. In some cylinders, the fuel mixture becomes rich, in some – lean. Vibration, misfires – problems guaranteed.
If the NOx system is “turned off” incorrectly, DME has problems also with evaluations of the performance of other hubs and restoring of their adaptation maps. As we see by the error messages and mystical problems, in this current case, all fuel self-testing and self-adjustment systems are paralyzed. DME reports nonexisting problems in them. The situation is also worsened by unexisting measurements of the injectors: DME does not know the true amount of used fuel. It is especially essential in the moment of the cold start at the moment when Lambda probes (and even air mass meter) have not started to work. And, if some injector is leaking even for a little bit – the complete crash of the system is guaranteed!


What has to be done to this car?
At first – repair what others have broken. Restore the stock software.
Then – the performance of the NOx system has to be restored.
Then – re-adaptation of the engine has to be performed.
Only after this initial repair, the data of the injectors will be available, and it will be possible to evaluate their “health”. My experience says – with a probability of 99%, there will be no problems with HPFP.
Unfortunately, the NOx catalytic converter is permanently damaged. Without illusions – also the “health” of the CO catalytic converter is severely damaged. In the worst case, they have to be replaced, for the customer, it will cost around EUR 1500.


In the end.
Technical nuance, which I always check for these engines: does the DME manages and how manages to maintain the oil pressure.
Appropriate data available here: ../F6/F2/F2 un ../F6/F2/F3

Atypical for N53 (unlike N43, who very often had such problems), but this engine also has problems with maintaining the oil pressure:

Such PWM of the oil pump indicates that the bypass valve is almost closed. It is not good news. Correct indication: at least 40%.
It is possible that the valve itself has problems – the repair will be cheap. But if the oil catcher is clogged of the flowrate via bearing shells is increased – the repair of the engine can cost a lot.

To be continued.