P0426 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. 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.

Likely causes

Symptoms

• 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

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov, hella.com.