Citroen C4 Overvoltage Errors

Excessive voltage within a vehicle's electrical architecture can indeed trigger a cascade of system failures, as modern cars rely heavily on stable voltage levels for proper operation. Given the symptoms you've described, it's plausible that a malfunctioning voltage regulator within the alternator is the primary culprit, leading to overcharging and subsequent system-wide errors. Alternatively, a severely degraded battery, exhibiting internal shorts, could also present with similar overvoltage indications due to the charging system's attempts to compensate. Have you measured the battery voltage both at rest and while the engine is running? These measurements could offer valuable insights into the source of the problem.

Thanks for the quick reply! I haven't checked the voltage with a multimeter yet, but I will. Where exactly is the voltage regulator located? Is it part of the alternator, or is it a separate unit? And if the battery is shorted, would that really cause an overvoltage? I thought it would cause a voltage drop!

The voltage regulator is typically integrated into the alternator assembly itself. Its function is to maintain a constant output voltage, usually around 14 volts, regardless of engine speed or electrical load. While a shorted battery usually causes a voltage drop, a heavily discharged or defective battery can, in certain circumstances, create unusual load scenarios that the charging system misinterprets, leading to voltage fluctuations and potentially overvoltage conditions. Considering the complexity of modern vehicle electrical systems, I strongly recommend a comprehensive diagnostic assessment by a qualified technician to pinpoint the root cause accurately. Ignoring the issue might lead to further damage to sensitive electronic components. A defective battery needs replacement. Budget around 290€ for the repair.

You were spot on! Took it to a shop, and it turned out the battery was completely shot. They replaced it, cleared the fault codes, and everything's back to normal! Thanks a million for the advice; I really appreciate it!