Complaint Instrument cluster warning lamp and/or warning message for brake system, EPB, ESP (yellow or...

Bulletin number

LI42.45-P-079407

Component

Electrical system

Summary

Complaint Instrument cluster warning lamp and/or warning message for brake system, EPB, ESP (yellow or red) and possibly 12 V battery (red) Different combinations of the following DTCs present in the ESP: B23AA77, B23AB77, B23D177 and in part (C100BE0, C100BE1, B23AA1B, B23D152) Cause Due to a reduction in resistance at the HV voltage divider, the DC/DC converter measures an incorrect HV voltage. Regulation of the 12 V output voltage therefore becomes unstable. I.e. the output voltage starts to fluctuate and the output current starts to jump instead of slowly regulating to the currently requested value. The EPB position is calculated by the voltage and the current. Since these fluctuate, the ESP control unit loses its position and sets the DTCs. Remedy Check of the DC/DC converter via XENTRY Diagnosis: • Compare the serial number of the DC/DC converter with a list of potentially affected parts in XENTRY -> DC/DC converter N83/1 -> Special Processes. • If the evaluation comes back as defective - Replace the DC/DC converter and inspect the EPB for Subsequent complaint, defect. • If the evaluation comes comes back not affected: Actuate BUCK mode for approx. 30 s • The output current normally jumps to a high value (e.g. 100 A) and then falls slowly to the current specified value e.g. 50 A and then only changes slowly and in small increments. • In the event of this fault cause, the output current is subject to strong fluctuations/jumps (multiple 1-10 A) (see videos in attachment). • In the event of strong fluctuations and the S/N not identified in the Special Process, please open a TIPS case and attach print out of DC/DC special procedure and buck mode actual values. Subsequent complaint, defect on the EPB: • Check of the actuators and brake caliper piston • Manually extend and retract the piston on the brake caliper completely using the suitable socket • If the piston sticks at a certain point, the rotation force increases significantly • If the brake caliper piston sticks, the brake caliper has to be replaced • If the retaining ring of the actuator is broken, the actuator has to be replaced • In XENTRY, edit the stored test instructions of the remaining DTCs

Owners of these vehicles have filed 105 complaints in the electrical category.