E39 / P0621 00

Read the instructions below then start the fault diagnostic procedure.

Symptom: Warning lamp lights.

P0621 00

Fault symptom

Warning lamp lights.

On-board diagnosis

Type of diagnosis:

Continuous

Enable criteria:

Test 1

Ignition on for at least 5 s.

Engine Stopped

Test 2

Engine running more than 20 seconds.

Fault criteria:

Test 1

Control module output short-circuit to B+.

Test 2

Open circuit in control module output.

Or

Control module output short-circuit to ground.

Checking the wiring harness

Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short-circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force.

Diagnostic help

Diagnosis regards:

Electrical fault in connecting leads or component.

Generator connection for field current (DF). Originates in the internal regulator and shows the amount of period length for which the generator applies field current. Used to calculate generator torque requirement.

Functions in the diagnostic tool related to the fault:

Test value:

•	Alternator F Terminal

•	Alternator L Terminal

Activation:

•	Alternator L Terminal

(See also description of readings/activations in diagnostic tool)