OBD-II code family
Heated Catalyst Temperature Faults (2 codes)
2 related fault descriptions. Use each full code and the exact vehicle service information to identify its circuit, monitored condition, and required tests.
Codes in this family
This is the complete published member list for this guide. Each code retains its own page; shared diagnostic context does not mean that every member has the same test or repair.
What these codes mean
P0424 and P0434 identify heated-catalyst temperature below threshold for banks1 and2 respectively. They describe the monitored temperature outcome. They are different from low sensor input P0427/P0437, heater-control P0429/P0439 and heated-catalyst efficiency P0423/P0433.
Identify how the installed monitor obtains its temperature result, its operating prerequisites and the exact monitored assembly. The title alone does not supply a physical sensor location, a fixed number of seconds from a cold start or a thermostat diagnosis. Do not dismiss a stored fault solely because the vehicle makes short trips or operates in cold weather.
Preserve the fault data. Verify relevant inputs and investigate associated engine, sensor and heating faults in the stated order. A calculated temperature field does not prove that a sensor exists at that position, and a normal opposite bank does not by itself establish the cause on this bank.
Heater testing requires the correct architecture, isolation and rated equipment. Have the prescribed checks performed before replacing a heating element, controller, sensor or converter. The parts listing determines whether a confirmed failed element is separately serviceable.
After repair, use the approved procedure to confirm the monitored temperature criterion. Clearing a warning or completing an arbitrary drive is not the same as verifying the fault. Base driving decisions on actual symptoms and warnings rather than assuming warm running removes every consequence.
Identify the circuit on your vehicle
Match the full DTC, reporting module, and any failure-type suffix to the service information for your exact year, make, model, engine, and equipment. An identifier alone does not establish installed hardware count, location, connector pinout, or a universal measurement.
Where the manufacturer publishes its own meaning for this code, that is the one to work from — it describes the actual component on your vehicle, which the generic definition cannot. Keep the generic description for what it is good for: it tells you which subject area the standard assigned the code to, which is useful context when the two appear to disagree. If they do disagree, follow the manufacturer.