Case study for Mercedes (C- Class) 205 model series
Cause of the problem
- b21dc01 buffer battery of the EIS malfunction there is a general electrical fault
Fixing the fault
- At the c8 capacitor pin 2 = red 12v
- Pin 1 = earth brown
- Pin 3 = red/blue to EIS switch plug 1 pin 28, 30b voltage
To remove the C8 Park Pawl capacitor the following guidance was provided:
- remove the N/S/F kick panel trim
- remove the glove box under dash panel
- remove the N/S/F section of carpet
- remove the plastic panel on the floor against the bulk head
The C8 Park Pawl capacitor is bolted to the left-hand side of the electrics panel, remove the 8mm nut and lift out the voltage converter. This feeds in to the EIS at plug 1, pin 28 =30b voltage.
The voltage supply to the C8 Park Pawl capacitor comes from the rear SAM control unit in the trunk/ boot from fuse 448.
- K40/5 f448 (Electrical fuse 448) rear SAM (signal acquisition module).
- Check electrical lines, connections and connectors for damage, correct connection, loose contact and corrosion, and repair or replace if necessary.
- Check regulator and alternator.
- Additional battery.
- Replace C8 (Park pawl capacitor).