P0426: Catalyst Temperature Sensor Circuit Range/Performance Bank 1 Sensor 1
What to do
Usually driveable. Expect the sensor to be tested against the other temperature sensors rather than simply replaced.
What this code means
The bank 1 catalyst temperature sensor is producing readings within its electrical range but implausible for the conditions — reporting a cold converter after a long drive, or a temperature that does not move as the engine warms. A drifted sensor rather than a failed one.
Comparing it against the engine coolant and intake temperature sensors after an overnight stand is the quickest sanity check: all three should agree closely on a cold engine, and one that disagrees is the suspect.
Likely causes
Start here
- Faulty catalyst temperature sensor · moderate
- Sensor drifted out of calibration · moderate
Less common
- Corroded or loose connector · easy
- Damaged wiring harness near exhaust heat · moderate
Symptoms
Components involved
Information, not instruction
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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.
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