P04F3
Catalyst Heater Supply Voltage Bank 2
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.
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.
Common causes
- high
Heater supply voltage low or unstable
One of the most commonly reported causes for this code — check this first.
Typical part cost: $440-2750
- medium
DC/DC converter fault on heater rail
A plausible cause — test and verify before replacing parts.
Typical part cost: $440-2750
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Related codes
See related trouble codes
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Frequently asked questions
What does P04F3 mean?
P04F3 means "Catalyst Heater Supply Voltage Bank 2". It is a generic OBD-II code that points to a fault in the auxiliary emission controls.
What are the most common causes of P04F3?
heater supply voltage low or unstable; dc/dc converter fault on heater rail — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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