Powertrain, generic · Auxiliary emission controls

P0427 Catalyst Temperature Sensor Circuit Low Bank 1 Sensor 1

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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. P0427 means the signal voltage is below its lower limit – typically the signal wire is shorted to ground or the sensor is shorted internally. FCA's 3.0-litre EcoDiesel uses this sensor (middle of the oxidation catalyst and particulate filter unit), but no document available to us names this particular code.

Likely causes

Signal wire shorted to ground (chafed)
Sensor shorted internally
Water or corrosion in the connector
Engine module

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

DifficultyMediumDIY possible
Parts and labour€60–300
Time0.5–1.5 h

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

Parts involved

catalyst temperature sensor b1s1sensor wiringengine control module

Related codes

P0425P0426P0437P042CP0544P0420

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