P2251

DTC P2251 Linear HO2S Reference Ground Circuit/Open (Bank1, Sensor1)

Component Location:

DESCRIPTION

The linear oxygen sensor is mounted on the front side of the Catalytic Converter (warm-up catalytic converter) or in the front exhaust pipe, which detects a wide range of air/fuel ratio in the exhaust gas from rich to lean regions. This linear oxygen sensor produces a current that corresponds to a specific air/fuel ratio. The ECM monitors this signal and determines whether the air/fuel mixture is rich or lean. The ECM constantly monitors the HO2S and increases or decreases the fuel injection duration by using the HO2S signal, which is called closed-loop fuel control operation.

Detecting Condition & Limp Home:

DTC DETECTING CONDITION

1. DTC Description
The ECM monitors front O2 sensor signal level during fuel cut-off operation. This signal monitoring will determine open circuit of Reference Ground Circuit (ECM pin No. 53). The ECM sets DTC P2251 if front O2 signal during fuel cut-off is higher than predetermined threshold.
If the same error code is set in the next driving cycle, the ECM illuminates the MIL.

2. Conditions for Setting the DTC

Schematic Diagram:

Step 1 - 2:

Inspection Procedure