E300 Hybrid - going back to diesel sometimes fails

[Yasen Vladimirov]

Hello All,
I am glad I found this forum, seems to be very busy and full of friendly people

I am long time Mercedes user started back with 190D and now I have my dream car E300 Hybrid. But maybe this is my most expensive mistake

Anyways, I found a car, it took quite a bit to have it, due to quarantine. Since the price was too good I was aware that there will be some hidden problems.

Problem is the following, car runs well, charge and discharge high voltage battery, goes into electric and diesel just fine. But from time to time - it does not go back to diesel, it goes max power electric, stays for a bit and with a delay firesup the diesel or not and displays an error with to gearboxes and Malfunction.
I have some ODB reader and found two errors:

THE SIGNAL 'HOT START' FROM THE AUTOMATIC ENGINE START/STOP SYSTEM HAS A MALFUNCTION. THE SIGNAL IS INVALID / THERE IS AN IMPLAUSIBLE SIGNAL.

 

[V6Matty]

Could well be worth checking both the batteries in the engine bay, if they are weak it can send incorrect signals to things and give issues as you’ve seen

 

[Yasen Vladimirov]

I have just checked them in rest. Big one is at 12.50
The aux small one is at 13.50 which seems but high but i guess it is ok for aux agm battery.

 

[star]

I would say starter motor, the car uses the hybrid system on 1st start, then uses the starter for the stop start.

 

[Yasen Vladimirov]

I will go to local dealer for Star diag and check.
I see some errors in compressor as well and battery is cooled by compressor so it might be related as well.

Just a question is 12.5 good for the battery? On the diagnostics when igintion is on, it goes even to 12.1.

 

[LostKiwi]

A perfect battery is 12.6v no load after resting an hour or more. A marginal battery is under 12.4v. 12.5v is acceptable.

 

[alexanderfoti]

I will go to local dealer for Star diag and check.
I see some errors in compressor as well and battery is cooled by compressor so it might be related as well.

Just a question is 12.5 good for the battery? On the diagnostics when igintion is on, it goes even to 12.1.

An independent will save you considerable money, for an arguably better service.

12.5 is fine. You cannot determine the voltage when carrying out diag, as all the cars systems are on, and can pose 30+ amps load. IMO 12.1 when carrying out diag is fine, when it drops to mid 11 ish, then I would suspect battery.

 

[Yasen Vladimirov]

Hey, I went to a friend with Xentry - better service indeed.
So we wen't deeper int o the problem after checking some fuses and fixing them last error in the car is following:

P1CB700 The power supply for 30c is too low
it is not constant - so on the diag is displays 14.4 while running, but sometimes it goes to 8 volts and car disables the "auto shutdown" of the engine.
Extra info on the error is:

Check the supply to component A100s1
Check the connection between K88 (pyro separator) to N82/2 (BMS)

But this is where we ended up, since there were no schematics for this components.
I went deep into internet, didn't find much of information for K88

 

[John Laidlaw]

seems there is a Pyro fuse which shuts off power in the event of an accident

Just not sure where that's actually located? Maybe @alexanderfoti has some clue?

 

[John Laidlaw]

Could only find this through the power of Google and that's on an S class

 

[John Laidlaw]

B82 is a battery control module so check near the battery

 

[alexanderfoti]

The A100S1 is the battery back and the n82/2 is inside the battery pack, so I'd be checking that (high voltage) connection to the battery pack. Be careful, lethal voltages here!

 

[Yasen Vladimirov]

The A100S1 is the battery back and the n82/2 is inside the battery pack, so I'd be checking that (high voltage) connection to the battery pack. Be careful, lethal voltages here!

Thanks Alex, but can you elaborate more on that. I am aware of the hazard.

In terms of K88 the items shown in the picture of S-class is actually available in my car as well, in the box next to the steering wheel between the dash and drivers door. It is very hard to take it out, so it will take some time before I manage to get it out to review the connections.

 

[Yasen Vladimirov]

Just to summarize - my problem is the following.
Car runs well, it has green "ready" sign. Sometimes for example on long stop on traffic light, car starts on electric and the moment when i expect diesel to start it just stays on electric for 5-10 seconds then Engine starts and "ready" is now yellow. Car does not stop the engine anymore till I restart it.

The other similar case is - it just shows 2 gearbox wheels + Malfunction sign on the dash. After I restart it is all fine.

 

[alexanderfoti]

Thanks Alex, but can you elaborate more on that. I am aware of the hazard.

In terms of K88 the items shown in the picture of S-class is actually available in my car as well, in the box next to the steering wheel between the dash and drivers door. It is very hard to take it out, so it will take some time before I manage to get it out to review the connections.

Considering the codes point to a connection issue with both the battery AND the BMS. I would think the connection issue lies at the battery end rather than the K88

 

[Yasen Vladimirov]

Makes sense, but this is inside the battery right, not trivial i guess.

 

[Yasen Vladimirov]

Hi guys, sorry for the late reply.

Finally it was the starter motor indeed. Now going back from electric to diesel is working and no errors by far

 

[alexanderfoti]

Excellent! Thanks for letting us know

 

[sonic]

I would say starter motor, the car uses the hybrid system on 1st start, then uses the starter for the stop start.

A good diagnosis Star.

 

[star]

A good diagnosis Star.

Thanks.