General Precautions of EFI System Maintenance
F-97
128. P2196 Upstream Oxygen Sensor Deteriorated (Lower Limit of Deterioration Factor
Exceeded)
Description about Malfunction Cause:
Normally, air-fuel ratio of combustible mixed gas is changed between thick and thin alternatively.
Correspondingly, amplitude of oxygen sensor signal varies frequently as series of pulse. If sensor deteriorates,
its sensitivity to the mixture may decrease and the characteristic curve deviates, causing slow adjustment of
mixed gas. ECU can calculate deterioration factor as per relevant algorithm through rear oxygen voltage; if
calculation results show that deterioration factor is smaller than preset lower limit threshold value, it is
determined to be lower limit of deterioration factor exceeded.
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
P2195
P2195
Maintenance tips:
The malfunction has been confirmed, and the
following problems may possibly exist
1) Deteriorated sensor should be replaced.
Maintenance tips:
The malfunction has not been finally confirmed; wait
for ECU to fulfill the final test.
129. P2270 Downstream Oxygen Sensor Deteriorated (Oxygen Sensor Malfunction - Lean
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 enrich the mixed gas if it deviates from control target to be too lean. If
the voltage signal of sensor is not enriched in the desired direction and keeps to be too lean for a certain
period, the system will determine it to be the malfunction of oxygen sensor on the too lean side.
Malfunction Diagnostic Guide:
Required Equipment: (Diagnostic Instrument with EOBD Diagnostic Function, Digital Multimeter, and
Correct Circuit Diagram)
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
P2270
P2270
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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