DTC P2251: General 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 (bank 1, sensor 1) transmits a signal to the powertrain control module (PCM), and the PCM controls fuel injection duration by comparing the target air/fuel ratio with the rear A/F sensor (bank 1, sensor 1) signal. When the VSB1 terminal voltage is a specified value for a set time, the PCM detects a malfunction and stores a DTC.