P0437: Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 1

What does P0437 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 1 of bank 2 is the first catalyst temperature sensor on the side without cylinder 1. P0437 means the signal voltage is below its lower limit – typically the signal wire is shorted to ground or the sensor is shorted internally. 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 Signal wire shorted to ground (chafed)
• Medium Sensor shorted internally
• Medium Water or corrosion in the connector
• Low Engine module

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