P0429: Catalyst Heater Control Circuit/Open Bank 1
What to do
Driveable, will fail an emissions test. The repair is often a relay or wiring rather than the converter assembly.
What this code means
A fault in the circuit that controls the bank 1 catalyst heater. The heater draws a substantial current and is usually switched through a relay, so this code concerns the control side — the module's output, its wiring, and the relay coil — rather than the heating element itself.
As with the secondary air pump, test the relay before the expensive component behind it.
Likely causes
Start here
- Failed catalyst heater relay · easy
- Open or shorted heater control circuit · moderate
- Corroded or loose connector · easy
Less common
- Failed catalyst heater element · specialist
Rare
- Control module driver failure · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0429.