P0620: Alternator output monitoring and occurrence history

BMW fault 210201/P0620 monitors whether the alternator is supplying power. The N63 chart identifies incorrect positive or ground connections, a regulator defect, and alternator failure as possible origins. It also expressly notes that the fault can occur during servicing with an external power source connected.

Conditions behind the result

This monitor requires the engine to be running and the alternator not to be fully loaded. Its fault-memory delay is longer than 25.5 seconds. The published enable logic also refers to requested alternator voltage relative to the vehicle electrical-system voltage. These conditions mean that a single voltage measurement taken in an unrelated operating state is not equivalent to reproducing the monitor.

The service-related warning changes the history that should be collected. A one-time entry immediately after charging or workshop support is different evidence from a repeatedly logged fault accompanied by a charge warning during normal operation.

A fault count influences service action

The chart first directs checks of positive and ground installation and the alternator itself. For a frequency of one, it distinguishes whether BMW's IMIB test equipment is available; with that equipment an alternator test is specified. Repeated occurrences move the chart toward alternator replacement.

This does not justify ignoring an active charging concern. The source lists a charging warning and, in extreme cases, a breakdown. A technician should establish current charging operation and connection condition, then use the occurrence history to interpret the stored entry rather than automatically condemning the alternator from the generic code title.

Source and applicability

BMW diagnostic chart, P0620. 2011 BMW X6 xDrive50i (E71), N63 4.4L turbo; BMW DME monitor chart reproduced by Operation CHARM. These values describe that documented monitor; they are not universal specifications for every vehicle displaying this code.