Why diagnostics, performed by dealer, fail

Many people are opposing – it’s not possible, that authorized dealer of BMW AG can not detect defects for engine, manufactured by BMW AG!

So, for today I’m going to pretend to be a diagnostics specialist from authorized dealer center. Step by step I will perform exactly those activities, which are performed by such specialist. Let’s see, how it will work out!

Patient: N53B30 O0. No reclamations regarding performance of engine. In the program – planned maintenance and computer diagnostics.

At first, we have to keep in mind, that the only diagnostics software, available in BMW AG deal centers, are DIS +SS/SSS (second generation before actual one), ISTA D and ISTA P (previous/actual generation), ISTA + (latest generation). BMW offers also, for example, TIS (system of technical information), WDS (database of schematics), EBA (installation of accessories). But the dealer BMW AG dealer centers don’t use (officially – are not allowed to use), for example, INPA, not even talking about NCS Expert, Tool32 or WinKPF.

So I, as a diagnostics specialist of authorized dealer center, will use available (allowed) software (ISTA D), perform identification of vehicle.

After successful identification, I perform the reading of error messages.

And ask the system to show the error message list.

In current case, two error messages, related to DME MSD80, are detected:

a) error message regarding incorrect coding;

b) error message regarding uneven running (very well known error message 3104; why this error message appeared in this list – read in the end of article).

In this current situation, error message regarding incorrect coding is registered, because the engine has been refurbished from version U0 to version O0, but the software release has been chosen from E61 (which does not corresponds FR). True thou, the MSD80 can display the same error message also after choosing the correct version of software. In appropriate TIS document from BMW AG is written, that the cause, why this error message appears, is not clear, status is marked as “under investigation”. Unfortunately there are no TIS documents, which would confirm, that the problem is solved. When choosing to solve the problem of this error message, ISTA D offers to perform re-programming using ISTA P, but this error message in no way affects further algorithms and diagnostics procedure, which are offered by ISTA D, if the error message 3104 is recorded.

Also error messages regarding NOx sensor don’t changes test algorithms of ISTA D for analyzing 3104 error message. No changes will follow, even if the error messages regarding misfire if current cylinder, trim of Lambda probes, error messages regarding fuel trim are recorded.

As required by ISTA D, press the key: calculate the test plan.

ISTA D has calculated the test plan. As highest priority – problem of incorrect coding. Knowing the reason of this error message, I skip the programming session of ISTA P and switch directly to solving of error message 3104.

And so the first “surprise”  – the error message 3104 has no description! One of the most popular problems – but there is no additional information, zero.

There, already more complete answer – connection of ignition coils and very general sentence, that there could be several causes for this problem. But I must add, that if there would be problems with connection of ignition coils, MSD80 would recognize it and record the corresponding error message.

But there is no wide choice – let’s start with “basic” section.

This menu is very decisive in all action line of this ISTA D algorithm. Unfortunately, the text of menu is the same as for all other petrol engines, elements of NOx system are not identified separately.

Very seasoned diagnostics specialist knows very well, what steps will follow, if he will choose to confirm, that also other engine systems have error messages. Let’s suppose, that we perform this procedure of diagnostics for the first time, so I honestly make a mark – yes, other systems have problems (let’s suppose, there are error messages regarding fuel trim, NOx sensor or 30EA regarding sulfuring of NOx catalytic converter).

The direction clear – at first solve these/other problems.

And so the analysis of error message 3104 problem is finished. Of course, problems with Lambda probes (if such are present), has to be solved as first. But, if there are error messages regarding NOx catalytic converter and/or NOx sensor, there could be false error messages regarding Lambda probes, CO catalytic converters present, also if the knots are performing correctly.

Moreover, if the NOx system is damaged, many customers do not want to spend more than EUR 2500 – 3000 for replacement of sensor and catalytic converter and are ready to settle with increased fuel consumption. None of TIS documents has information, that the defects of NOx system can cause problems with adaptations and uneven performance of engine, misfires, false error messages regarding performance of NOx catalytic converter, performance of Lambda probes (description here).

So – if in the comment of ISTA D would be exact explanation regarding NOx system as a cause of specific error messages; if the NOx system would be included in a list of knots, problems of which should be solved as priority; if ISTA D would not allow to perform misfire tests if there individual corrections of cylinders are incorrect (or does not exist at all); if customers would ready to perform the repairs of NOx system, despite the high costs – no false error messages would be present. To many “if”. But we continue with existing situation.

Knowing, that the confirmation, that other knots has problems, will simply finish solving of error message 3104 problem, the diagnostics specialist will choose option – ‘no’, this engine has no problems with other systems.

Let’s repeat the test again.

But in this case we choose to press: no, there are no problems with other systems.

This time ISTA D informs, that the low pressure pump will be checked.

When we confirm the choice, the test of low pressure pump will be performed (after it will be switched off).

The pressure of low pressure pump will be checked during 15 seconds (fuel pressure before high pressure pump).

No problems in low pressure pump performance identified.

ISTA D has found problematic cylinders! Good news? Or not?

In current situation – error message 3104 was recorder 6 – 10 driving sessions ago. Reason – very uneven road. You have to take in account, that ISTA D will not delete the error messages regarding damaged cylinders, even if the engine will perform perfectly for a longest while. Conclusion – even, if the uneven running was before 50’000 km and solved a long time ago, ISTA D will still report the “damaged cylinders” (if only the dealer specialist has not performed this test procedure, which has resulted with deleting of adaptation data and misfire counters).

In the next step, ISTA D allows to check ignition coils – if the ignition coils of very old series are installed, they has to be replaced.

In 99% the ignition coils will be replaced for at least several times, because 3104 is a typical problem.

In the next step ISTA D informs, that the test of injectors will be performed.

Something more interesting – you would think, when performing this test for first time. But…

It turns out, that the injector test is performed for cold engine!

Yes, BMW AG has developed a specific tool to activate cooling fan – the engine is cooled much more quicker with using it, but… Unfortunately, this tool is a rarity even in authorized dealer centers (it’s used very rarely), the vehicle must be connected to extra power supply. Besides, this procedure requires quite long time (in this case the proverb “Time is money” is just in time).

I think I will not be wrong, if I will say, that in most cases nobody waits, till the engine has cooled down, but continues the test plan.

In current (also as in main part of other situations) case, the test for injectors of cold engine will not discover any new defects, but faithfully repeats, that cylinders 1 and 5 are damaged. In turn, if the test of injectors for cold engine would discover any abnormal signs for any injector, other cylinders will be added to already “damaged” No.1 and 5. Most probably those cylinders perform perfectly, and the cause of problem is incorrect individual adaptations due to damages of NOx system.

Next step of test plan repeatedly inquires about problems of cold engine. If we choose yes, ISTA D will offer to cool down the engine and then perform the test.

That’s why we choose not to repeat this step.

Now the first recommendations follow. Replace the ignition coils for cylinders No.1 and 5. Ignition coils have been changed compellingly recently – before 20 .. 30k km).

Data of spark plugs would be checked.

And the next recommendation – replace the spark plugs of suspicious cylinders. Well, the spark plugs has been changed around 10k km earlier. But, if ISTA D say’s so…

And there – also question regarding injectors.

Diagnostics specialist, who has performed this test for several times, knows very well, that if the answer will be “yes” – ISTA D will offer to replace these injectors.

I choose to answer “no”, because the injectors has been replaced 50k km earlier.

It look’s that, regardless of answer, ISTA D will offer to replace injectors for suspicious cylinders!

And now – the last step: deleting of adaptations. And with this the test block of error message 3104 is finished. Bill to the customer: at least EUR 900 (two injectors, two ignition coils, all spark plugs, diagnostics work, coding of injectors).

And at the end: misfire counters. They were read, using EML327 adapter via OBD 6 mode (nor ISTA D, nor INPA does not shows them).

As you see, both short term and long term misfire counters are 0! It means, that the engine has “fixed itself”! This is a great example, that the formal (dealer) approach is not the best solution. Nothing can be blamed on dealer’s diagnostics specialist, because they are very limited in choice of equipment and methods. And still – a typical bill in case of solving error message 3104 problem reaches EUR 1000 and more, and we – customers – pay for solving of non-existing defects.


Related entries:

Misfire detection algorithm and it’s fails

MSD80 ”features”

N53B30. When adaptations failed

N43 with strange behavior