P0426Catalyst Temperature Sensor Circuit Range/Performance Bank 1 Sensor 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Some engines – mainly diesels – measure the temperature at or in the catalyst with a thermistor in a voltage divider instead of only modelling it; most makers report exhaust temperature sensors under P0544 ff, P2031 ff or P2080 ff instead. Sensor 1 of bank 1 is the first catalyst temperature sensor on the side with cylinder 1. P0426 means the signal is electrically valid but implausible – compared with the temperature model or neighbouring exhaust sensors it is off, sluggish or frozen. Only FCA's 3.0-litre EcoDiesel (Ram 1500 and Jeep Grand Cherokee, 2014/15) is documented with this sensor: it sits in the middle of the oxidation catalyst and particulate filter unit, a platinum element with 200–240 Ω at room temperature; the bulletin for P0426 advises blowing soot off the tip, measuring and replacing it, plus a software update.
- What you may notice
- Check engine light on
- Usually no noticeable change (substitute value from the model)
- Diesel: filter regeneration distorted or blocked, possibly further codes such as P2459 or P0420
- Likely causes
- LikelySoot on the sensor tip (diesel)
- PossibleSensor aged, characteristic drifted
- PossibleContact resistance in connector or wiring
- PossibleEngine module software (plausibility limits)
- RareExhaust leak upstream of the sensor
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.