Powertrain, generic · Auxiliary emission controls

P042D Catalyst Temperature Sensor Circuit High Bank 1 Sensor 2

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 2 of bank 1 is a second, further downstream catalyst temperature sensor on the side with cylinder 1. P042D means the signal voltage is above its upper limit – typically the sensor or its wiring is open, or the signal is shorted to positive. No manufacturer document available to us uses this code; the description follows CARB, which requires input circuits to be checked for circuit faults and plausibility, and the comparable exhaust temperature sensors.

Likely causes

Sensor or wire open (broken by vibration or heat)
Connector off or loose, ground wire open
Signal wire shorted to positive
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 b1s2sensor wiringengine control module

Related codes

P042AP042BP043DP0428P2031P0420

References: law.cornell.edu, hella.com, gsi.ext.gm.com.