OBD Catalyst Heater Supply Voltage Bank 2
What it means
P04F3 stands for Catalyst Heater Supply Voltage Bank 2. P04F3 is a P code, so the fault sits in the engine, transmission and emissions systems. For P04F3, the second digit places it in auxiliary emission controls. For P04F3, work through the cause list below, cheapest checks first.
What to check first
For P04F3, compare the reading on bank 2 against the other bank on the same scan tool, because a bank that reads differently from its twin is the fault.
Check these first
- P04F3: Carbon buildup or blockage in the EGR, EVAP, or air injection system
- P04F3: Failed solenoid, valve, or pump in the auxiliary emissions circuit
- P04F3: Wiring, connector, or fuse fault for the emission component
- P04F3: Small leaks in vacuum or EVAP lines
- P04F3: Failing catalytic converter or oxygen sensor reporting incorrectly
What to do next
P04F3 belongs to the auxiliary emission controls system. These are the general steps for P04F3, and the exact cause on your vehicle can differ.
- P04F3: Read related codes and freeze frame with an OBD-II scanner
- P04F3: Inspect hoses, valves, and solenoids for leaks, cracks, or carbon buildup
- P04F3: Smoke test the EVAP or intake system if a leak is suspected
- P04F3: Command components on/off with a scan tool and watch them respond
- P04F3: Clean or replace the blocked or failed component
Look up another code
Enter a full code or a symptom. Press / to search. How to read a code
Type a code above, or start from a symptom or a common code.
Updated
Generic SAE J2012 definition. Last updated 2026-08-30.