General Precautions of EFI System Maintenance
F-98
130. P2271 Downstream Oxygen Sensor Deteriorated (Oxygen Sensor Malfunction - Rich
Mixed Gas)
Description about Malfunction Cause:
Under normal circumstances, the signals of downstream oxygen sensor shall fluctuate up and down the
control target value. The system will dilute the mixed gas if it deviates from control target to be too rich. If the
voltage signal of sensor is not diluted in the desired direction and keeps to be too rich for a certain period, the
system will determine it to be the malfunction of oxygen sensor on the too rich side.
Malfunction Diagnostic Guide:
Required Equipment: (Diagnostic Instrument with EOBD Diagnostic Function)
Step I: Use diagnostic instrument to read the malfunction information
Read Result I Read Result II
MIL Lamp On P-CODE Present MIL Lamp Off P-CODE Present
P2271
P2271
Maintenance tips:
The malfunction has been confirmed, and the
following problems may possibly exist
1) The performance of downstream oxygen sensor
reduced, and replacement required.
Maintenance tips:
The malfunction has not been finally confirmed; wait
for ECU to fulfill the final test.
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