Question by MarkM posted 4 months 2 weeks ago in GLK-Class

After several $500-$1000 visits to our mechanic for various emissions system issues we had our GLK 250 DPF replaced with a straight pipe, the Blutec system blocked and the EGR valve closed. All related sensors etc were tuned off. This work is completely legal where we live. We are now experiencing misfiring while accelerating from a stop or slow speed to about 25-30 mph and through D1, D2, D3 up to D4. It feels like the car is "shuddering" for a couple of seconds. It can be a couple of hours of driving between incidents and tends to happen most often just after the vehicle has been parked and turned off for at least a few minutes. I have an Autel diaglink scanner with Benz software. It is showing no codes except the following for module 22 "FSCU FUEL PUMP":

  • C1 0000 Communication with the engine control unit is malfunctioning
  • C1 5500 Communication with the instrument cluster is malfunctioning
  • C1 6800 Communication with the electronic ignition switch is malfunctioning

I can't find any info on these codes. Any ideas out there on whether the emissions work is related to the misfire and these codes? And/or how to fix the issue?