P0426 — Heated Catalyst Temperature Below Threshold (Bank 1)
Drive with caution — fix soon.
What P0426 means
This code means the catalyst temperature sensor on bank 1 is reading lower than the computer expects, suggesting the converter isn't heating up properly. The cause is often a faulty temperature sensor or its wiring, but a genuinely underperforming catalyst or an exhaust leak can also trigger it. Diagnosis usually starts by checking the sensor and circuit before considering a converter replacement.
Common symptoms
- Check engine light is on
- Failed emissions or smog test
- Slightly reduced fuel economy
- Often no noticeable change in how the car drives
- Occasional faint exhaust odor
Common causes
- Faulty catalyst temperature sensor
- Damaged wiring or poor connector at the temperature sensor
- Exhaust leak before or near the catalyst
- Underperforming or aging catalytic converter
- Engine running cold due to a stuck thermostat
Typical repair cost
$150 – $1800
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0426 code?
Usually yes, since it rarely changes how the car drives. The main concerns are extra emissions and a possible smog-test failure. Get it diagnosed within a week or two so a small sensor issue doesn't get mistaken for a costly converter problem.
How much does it cost to fix a P0426?
If the fix is a temperature sensor or some wiring, it's often $150 to $450. If the catalytic converter is genuinely failing, the repair can climb to $900 to $1,800 depending on your vehicle.
Is a P0426 code serious?
It's a low-to-moderate concern. It won't typically leave you stranded, but it signals your exhaust isn't being cleaned as intended. Address it before an emissions test or before a sensor fault is mistaken for converter failure.
Is P0426 usually a sensor problem or the catalyst itself?
More often than not it's the temperature sensor or its wiring rather than the converter. Because the sensor is far cheaper, a good technician will test it first before recommending a new catalytic converter.