u/bogoz-bntd

Recently on the highway the iDrive gave a transmission warning (automatic), but no driving restrictions. Next day CEL is up. 2 days later when on highway again, iDrive transmission fault which put the car in limp mode and blocked transmission.

When we got home did a transmission reset (with floowing pedal for 30 sec etc), which unlocked the transmission and lifted the limp mode. CEL was obviously still up.

I assumed it was a battery issue (knew its dying), aggregator was overworking (15.2V), went to quickly replace the battery at a random mechanic, installed and registered a new one, also resetted error codes. CEL was gone but came back a few hours later.

Got an enet cable to read codes and got some questions

EGR:

257E00 - Exhaust gas recirculation position sensor, signal: open circuit or short circuit to ground

• Q1: Does this mean EGR needs to be replaced or can it be just some fuse/wiring/sensor issue? Can it be issue with the engine ground strap?

DPF:

244800 Info - Particulate filter system: Limited residual running distance of the particulate filter available

If i understand correctly this is an automated message based on mileage (car has 208k km) and if the air pressure flow is okay then this can be ignored or resetted (with ISTA or some proper tool)?

Tried to measure with bimmerlink: ash mass: 47.7g, soot mass: 14.7g

• Q2: are these mass numbers okay (208k km on the clock)?

exhaust pressure in front of the DPF:

• ignition on (600-is rpm): 1.010 bar
• in neutral around 2.5k rpm: 1.066 bar

differential pressure across DPF:

• ignition on (600-is rpm): -0.013 bar
• in neutral around 2.5k rpm: 0.035 bar
  • -> these suggest me the airflow is fine, however interesting, the negative pressure makes me think if the sensor has some issues, not calibrated or dying?
• Q3: based on these pressure numbers, am I safe or does the DPF need attention?

Glow plugs:

241A00 - Glow control unit, diagnostic feedback: Engine configuration or glow plug type does not match the glow control unit

2AB900 - Glow plug control unit, diagnostic feedback: Mixed installation of different types of glow plugs detected

AFAIK these glow plug codes are up for a year or so, back then the mechanic said we can ignore them for now and see if they come back. I tried to research and can mean different things, like plug mismatch or simply they weren't replaced at the same time or their resistance differs, or the gp control unit failing...

• Q4: How worried should I be regarding this glowplug mismatch, can it affect the cars other parts like EGR or DPF? Does it affect DPF regeneration? Should all plugs be replaced? Does the glow plug control unit need replacement?