Possible causes

– Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 harness is open or shorted
– Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical connection
– Faulty Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P2251 Description

The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. The rear A/F sensor transmits a signal to the powertrain control module (PCM), and it enables overall feedback control. The PCM controls fuel injection duration by comparing the target air/fuel ratio with the rear A/F sensor signal. When the VSB1 terminal voltage is more than a specified value for a predetermined time, the PCM detects a malfunction and stores a DTC.

P2251 Information for specific makes

P2251 ACURA
P2251 DODGE
P2251 HONDA
P2251 HYUNDAI
P2251 SCION
P2251 LEXUS
P2251 TOYOTA