P0426 code meaning
Catalyst Temperature Sensor Circuit Range/Performance Bank 1 Sensor 1
Powertrain system Generic code P04xx codes Check engine light
What P0426 means
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.
P0426 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0426
- 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
Common causes of P0426
- Most likelySoot on the sensor tip (diesel)
- PossibleSensor aged, characteristic drifted
- PossibleContact resistance in connector or wiring
- PossibleEngine module software (plausibility limits)
- Less likelyExhaust leak upstream of the sensor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Catalyst temperature sensor b1s1Sensor wiringEngine control module
What each part of P0426 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 26 | The exact fault in that area. |
What to do next
- Note P0426 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0426
What does P0426 mean?
P0426 means "Catalyst Temperature Sensor Circuit Range/Performance Bank 1 Sensor 1". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0426?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0426 fail an emissions test?
Yes, it can. P0426 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0426 to fix?
Difficulty: medium. A typical repair takes 0.5 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0426 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.