P043A: Catalyst Temperature Sensor Circuit Bank 2 Sensor 2

What does P043A mean?

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 2 is a second, further downstream catalyst temperature sensor on the side without cylinder 1. P043A is the general circuit fault, used where the module does not separate low and high. 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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

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

Common causes

• High Sensor faulty (element or lead broken by heat or vibration)
• High Harness chafed or scorched at the exhaust, connector corroded
• Medium Connector loose or pins pushed back
• Low Engine module input

Likelihood is a general estimate across vehicles; your make and model may differ.