P04F3
Catalyst Heater Supply Voltage Bank 2
What it means
The electric catalyst heater on bank 2 - used on hybrids and modern petrol cars to bring the catalyst above light-off temperature within seconds of cold start - reports that its supply voltage is outside the expected window. The heater cannot deliver the rated power, so cold-start emissions rise until the catalyst reaches light-off conventionally.
Is it safe to drive?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Heater supply voltage low or unstable
highOne of the most commonly reported causes for this code — check this first.
DC/DC converter fault on heater rail
mediumA plausible cause — test and verify before replacing parts.
Related help
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