Starting and Electronics Issues
The technician reports difficulties diagnosing a 2008 Mercedes C 350 vehicle whose engine will not start. The front wipers are also not functioning, and an error message appears on the instrument panel regarding brake issues. The stored error codes are B21272, B215F72, and B212171. The technician has tested the battery, which is in good condition. The fuses have also been checked and show no faults. Has this malfunction occurred before?
1. The described symptoms occur in the variant with the V6 gasoline engine, model year 2008. This is a relay malfunction affecting the main ignition circuits, secondary air pump, and engine control (see Figure 1).
2. The faulty relays were installed on vehicles within the following chassis number ranges:
204****A064140 – 204****A158064
204****F057431 – 204****F162917
204****R004400 – 204****R029520
Replacing these relays should resolve the faults. Do not forget to clear the error codes as well.
