N55 error messages, what's the root cause?

[widell]

Background:
My 2012 135 has been my daily driver for the last 5 years. It was originally sold in Belgium, and I imported it to Sweden in May 2015. It has been very reliable, and I've only ever been to the shop with it for regular maintenance until now.

Issue:
Last time I drove it, I got an engine warning and the car went into limp home mode. Today, I took it to the same shop that performed the last service a few weeks ago for a quick diagnose. They hooked up the diagnostics and found 8 codes. The descriptions were in Swedish, but I found a PDF with the N55 error codes on the forums:

2DD6 - Valvetronic servomotor, position sensors: Short-circuit or line break (open circuit)
2DD8 - Valvetronic servomotor, position sensors: Signal implausible
3876 - Battery Management: low voltage (My translation of the Swedish description in the papers from the shop. The description for this code in the PDF was blank)
36E2 - DME, internal fault, monitoring 5V sensor supply: Voltage outside valid range
2DD7 - Valvetronic servomotor, position sensors: Supply voltage faulty
27E8 - Accelerator pedal module, pedal position sensor, plausibility: synchronisation error between signal 1 and Signal 2
27DA - Accelerator pedal module, pedal sensor 1, electrical: Short circuit to earth or line disconnection
281B - Absolute pressure sensor, intake pipe, electrical: Short circuit to earth

They asked me if I had done anything battery related recently, and I said no. They said they would clear the codes and see what came back again after I drove it a little. They were able to clear all but two codes:

2DD7 - Valvetronic servomotor, position sensors: Supply voltage faulty
36E2 - DME, internal fault, monitoring 5V sensor supply: Voltage outside valid range

They said they would need to bring it in to be able to find the root cause. I will book an appointment soon, but I thought I might get some advice from experienced owners here first.

On the drive home, I noticed the idle went up to ~1500 rpm for a couple of seconds a few times. When I got home and turned it off, the battery warning came on, so I guess that code is back now. I haven't changed the battery since I bought the car, so it is most likely 8 years old.

Another thing that might be related is that I've heard a new sound a few times when unlocking the car lately. I think it's the LPFP that sounds less like a humming, and more like a "krrrrrrr" sound. I didn't make much of it at the time.

What do you think is the root of it all?

Only knowing what is in this post, and not having much experience myself, I guess I would start with the battery. My thinking is that there is a possibility that a bad battery could cause the other problems, but it doesn't make much sense the other way around. Low battery voltage -> Low sensor feed voltage -> bunch of sensor errors.

[dtla1]

Originally Posted by widell

Background:
My 2012 135 has been my daily driver for the last 5 years. It was originally sold in Belgium, and I imported it to Sweden in May 2015. It has been very reliable, and I've only ever been to the shop with it for regular maintenance until now.

Issue:
Last time I drove it, I got an engine warning and the car went into limp home mode. Today, I took it to the same shop that performed the last service a few weeks ago for a quick diagnose. They hooked up the diagnostics and found 8 codes. The descriptions were in Swedish, but I found a PDF with the N55 error codes on the forums:

2DD6 - Valvetronic servomotor, position sensors: Short-circuit or line break (open circuit)
2DD8 - Valvetronic servomotor, position sensors: Signal implausible
3876 - Battery Management: low voltage (My translation of the Swedish description in the papers from the shop. The description for this code in the PDF was blank)
36E2 - DME, internal fault, monitoring 5V sensor supply: Voltage outside valid range
2DD7 - Valvetronic servomotor, position sensors: Supply voltage faulty
27E8 - Accelerator pedal module, pedal position sensor, plausibility: synchronisation error between signal 1 and Signal 2
27DA - Accelerator pedal module, pedal sensor 1, electrical: Short circuit to earth or line disconnection
281B - Absolute pressure sensor, intake pipe, electrical: Short circuit to earth

They asked me if I had done anything battery related recently, and I said no. They said they would clear the codes and see what came back again after I drove it a little. They were able to clear all but two codes:

2DD7 - Valvetronic servomotor, position sensors: Supply voltage faulty
36E2 - DME, internal fault, monitoring 5V sensor supply: Voltage outside valid range

They said they would need to bring it in to be able to find the root cause. I will book an appointment soon, but I thought I might get some advice from experienced owners here first.

On the drive home, I noticed the idle went up to ~1500 rpm for a couple of seconds a few times. When I got home and turned it off, the battery warning came on, so I guess that code is back now. I haven't changed the battery since I bought the car, so it is most likely 8 years old.

Another thing that might be related is that I've heard a new sound a few times when unlocking the car lately. I think it's the LPFP that sounds less like a humming, and more like a "krrrrrrr" sound. I didn't make much of it at the time.

What do you think is the root of it all?

Only knowing what is in this post, and not having much experience myself, I guess I would start with the battery. My thinking is that there is a possibility that a bad battery could cause the other problems, but it doesn't make much sense the other way around. Low battery voltage -> Low sensor feed voltage -> bunch of sensor errors.

I would agree with you and start with the battery, especially if it's still on the original.

[lforter]

Did you found the problem? According to other post it sounds like a bad servomotor, mine has the same problem but car won't start, although, it doesn't makes the clicking sound.

[shawnyeeah]

I had a similar problem in my n55, changed battery and starter, still not starting. Found one of the battery cables in the engine bay was badly damaged (idk how), and had that replaced. No problems since then