Is It Safe to Drive With a P0620 Code?
Common Symptoms of a P0620 Fault
EML and battery warning light
Possible battery not charging
Dim lights
Multiple electrical issues if charging fails
Possible Causes of P0620
A P0620 code can be triggered by faults across several systems. Identifying the exact root cause requires proper diagnostic equipment and live data — not just reading the code.
Alternator Control Wiring Fault
Wiring to the alternator control terminal is damaged.
Alternator Internal Fault
The alternator's internal voltage regulator has failed.
Alternator Connector Fault
Connector to the alternator is damaged or corroded.
ECU Output Fault
ECU output controlling alternator field has failed.
Why we don't list the exact part: A P0620 code tells you what's happening but not why. Replacing parts based on the code alone is the most common way drivers waste money. A proper diagnosis identifies the specific cause first.
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P0620 and Your MOT
A stored P0620 fault code will cause your car to fail its MOT. The engine management light will be illuminated during the test — an automatic failure under current MOT standards. Even if the light temporarily clears, the code remains in ECU memory and can be read by testers.
Get the fault diagnosed and repaired first, then have the code cleared and confirm the light stays off before booking your MOT.