M54 Randomly Shuts Down While Driving + Crank No-Start Sometimes

M

Maximus_E85

New member
 germany
Hi everyone,
I'm hoping to get some peer confirmation on a sudden, shutting-down issue with my M54B25 engine before I start throwing parts at it. (E85 2004 2.5i)
The Symptoms:
While driving, the car will randomly and abruptly shut down completely. It does not stutter, misfire, or drop into Limp Mode; it feels exactly as if someone pulled the main power plug on the engine computer.(After parking under the 35deg sun for a month without any action.)
  • Sometimes, it will fire right back up after pulling to the side of the road.
  • Other times, it refuses to start immediately. It will crank endlessly but won't catch. If I let the car sit and cool down for 5 to 10 minutes, it suddenly fires up completely normally.
The Voltages:
  • Battery resting (Engine Off): 12.5V
  • Alternator output (Engine Running): 13.9V
    (The charging system and battery appear healthy)
The OBD 2 Code from the engine:
- 2806 Cruise control: time limit of data transmission reached
- 27C3 Thermal oil-level sensor
- 28B2 Speed limitation: reset
- 27F8 Pedal position sensor, potentiometer 2
- 2741 Pedal-position sensor 2:
voltage supply
- 27C4 Main relay
- 27C7 Main relay: switching delay

What should I do next?
Before reading the codes, I originally thought these symptoms pointed directly to a failing Crankshaft Position Sensor (CPS), given how common it is for them to cut out when hot and refuse to restart until cooled down.

However, seeing this massive cluster of DME power, pedal sensor, and cruise control codes makes me think it’s strictly an electrical delivery issue feeding the DME itself rather than a sensor position fault.
Does anyone have any extra tips, or is swapping that sky blue relay and unplugging the oil level sensor the absolute best next move? Has anyone seen a bad ground strap cause this exact "switching delay" cascade on an M54?
Any advice on what else I should check while I have the E-box cracked open would be awesome. Thanks!

 
I know you have checked battery voltages but it could still be on the way out. I think my newish battery reads around 14 volts. How old is the battery, I would suggest if it's more than around 6 years old it could be worth buying a new one given the problems one reaching end of life can cause. Having said that I don't think an old battery would cause engine to shut down.
 
Hookup a fuel pressure gage to the schrader valve on the top of the fuel rail and turn the key to the on position and see if the pump pressurizes the rail.
 
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