Repair of IBS. Consequences

In one of the internet forums, its member wrote the following post:

“My story: INPA displayed 14.7 .. 14.8 V, without error messages. It seemed suspiciously too much. There was sometimes as shaking in idle (injectors and engine cushions were ok). One day the alternator died. After repair voltage was 14.1 V for a whole day, it goes without vibration. Repair kit from Valeo, including bearings.

In addition, there was a side effect – as lately was found out, 3 year of Deta Senator battery was dead and had to be replaced. My friend gave me OEM AGM from E91, which was almost 10 years old, but still “alive”.”


Several other participants of this internet forum asked me to comment on this situation. In addition, this is typical for an average “specialist”, so I decided to write this entry, which would describe the situation (and problems) after such repair as simple as possible.


The situation before and after “repair”

14.7 .. 14.8 V is a correct voltage! Exactly such voltage should be on battery clips if its (clips) temperature (which is measured by IBS sensor) is below +8 oC.

Instead, 14.1 V is an incorrect voltage – it’s very lowered. The voltage before “repair” indicated, that alternator was correctly managed via BSD, but after repair – not managed via BSD.

Next “problem” – during three years, the battery of known brand has been “damaged”. Why? Just because it wasn’t encoded (its replacement was not registered). If the replacement the of the battery is not registered, the battery is not used in full capacity (only part of its capacity is used), unused part of battery plates is sulfated (sulfuric acid “eats” them), and the battery loses its working ability. Even more, due to incorrect SOC (again – consequences of unregistered battery), the battery is kept in almost empty condition, and it’s not able to perform its function.

Now the owner of the car has installed AGM battery. Consequences? The situation is even sadder. AGM battery requires a higher charging voltage. But instead of required 15.0 .. 15.2 V (in low temperatures) it’s been supplied with only 14.1 V (in case a load of car onboard systems is not high) or – most often it’s just simply getting discharged (see further).


What are the consequences of such “repair”?

At first – problems with starting the car.

Taking in an account, that IBS system cannot work normally (perform tests and detect the capacity of a battery, SOC), correct preheating of glow plugs (for diesel engine) is disturbed. Accordingly – typical error messages regarding glow plugs (and then the “specialists” replace “relay” of glow plugs, glow plugs itself, wires – and again the same) are stored and its heating until starting the engine – canceled.

As already mentioned before, the charging of battery simply DON’T HAPPENS. The battery is gradually discharged. For this reason, it will get harder and harder to start the car. 14.1 V in cold (below 0 oC) climate DON’T ENSURES charging of the battery (not in vain the IBS system increases such (14.8 .. 15.2 V) voltage on battery clips, not on alternator clips. What is the difference? The difference can reach even 0.5 .. 1.0 V – such as a voltage drop in wires if powerful consumers are turned on. Respectively – even in the alternator maintains required 14.3V (emergency mode) on battery, it will be only 14.3 – 0.5 = 13.8 V (or even less). Instead, if the alternator maintains 14.0 (old type regulator), on the battery it would be only 13.5 V!

One more unpleasant nuance: if the old type regulator has been installed on the alternator (with fixed voltage – which, most likely, is in this scenario: 14.4 V), after starting the engine, the alternator WON’T START to work! Only, when the RPM of the engine is increased – only when the alterntor starts to produce energy. Accordingly – all time after starting – while the engine will run in idle or with average RPM: the alternator won’t start to work. Accordingly – the battery will be additionally discharged.

In addition – as the IBS system (due to several causes: unmanagable alternator, unregistered battery) don’t work:

a) in case of increased discharge of the battery in KOMBI and CCC no appropriate icons regarding low charge level of the battery will not appear (and the redundant consumers will not be immediately disconnected, for example, multimedia system, car welcome lights, etc. in off state of the car);

b) in case of low charge level the consumers will not be sequently turned off during ”engine on” state;

c) no power management to save the battery resources will be organized.

Accordingly – earlier or later the car will stay in some remote area because you will not be able to start it. And then you will conclude, that “also AGM battery deceived”…


In addition to all problems – after “repair” the alternator works in abnormal conditions. If before the “repair” its max current was controlled and limited in moments when the alternator started to overheat, after the “repair” the alternator during the summertime can be damaged with very HIGH possibility – its diodes (and, possibly, also the regulator itself) will overheat. Taking into account the large consumption of electricity of cars of this generation, the alternator work close to max temperatures (with limited/decreased current) is a normal mode (it is specially mentioned in TIS). The basic operation principle of the system:

a) alternator informs DDE/DME regarding increased temperature of its stator or chipset;

b) DDE/DME reduces “appetite” of cars onboard consumers in such way, to ensure acceptable temperature of the stator or chipset;

c) when the temperature will drop till safe, DDE/DME will restore full power of the alternator.


Of course, if the inappropriate management module is installed on the alternator, it cannot inform anybody about its problems…

Only correctly performing IBS system protects the alternator from damages!

And finally – remark regarding vibration, which has disappeared mystically. Of course, there can be several causes, but one of them – in this (emergency) mode DDE doesn’t even try to smooth out the idle, performing the afterheat of the glow plugs. Respectively – the engine evenly (because the injectors are partly “alive”) vibrates, but vibration increases while warming up. The cause – the preheating of glow plugs has been not performed, DDE works in emergency (heating) mode. Possible cause of vibration before “repair”- some incorrectly working glow plug, which insufficiently heated the cylinder during warming up (in mode, when DDE tried to smooth out the idle, performing the afterheat of the glow plugs).



As other “unnecessary” systems, for example, EGR, flaps, also this – actually includes a serious “monster”, which performs an invisible work. As a result of a “repair”, performed by such “specialist”, the car actually was demolished. But it’s actually your choice – what kind of repair to perform: the one, mentioned before, or – put IBS in order.


P.S. I doubt the damages of the alternator, which were detected by this “specialist”. Very often these alternators are defected unreasonably. “Specialist”, most probably, assumed, that the alternator is damaged, because he saw (only) 12.8 .. 13.2 V onboard voltage for the turned on  car. Actually, the situation is a “bit” different:

a) as the replacement of the battery is not registered, SOH has a long time ago reached 0 or even negative value, the simulated capacity of the battery – calculated as tiny;

b) very quickly after starting the charging, IBS system makes a decision, that SOC has reached the optimal value (60 .. 80 %), accordingly – the charging has to be stopped;

c) to ensure a current balance of 0.0 A (to stop the charging), the voltage of alternator has reduced to 12.8 .. 13.2 V.

Such, as if reduced onboard voltage, can be the result of performance (also – correct performance) of the IBS system, not a defect of the alternator!

To detect the “health status” of an alternator, manageable via BSD, appropriate test blocks have to be performed and the live data of alternator has to be analyzed, not only the onboard voltage has to be measured!