Possible Causes
Faulty Air/Fuel Ratio (A/F) Sensor (Sensor 1)
A/F sensor (sensor 1) circuit range/performance
Fuel system too lean
Fuel system too rich
Secondary HO2S (sensor 2) circuit signal stuck lean
Secondary HO2S (sensor 2) circuit high voltage
Secondary HO2S (sensor 2) slow response
Engine Misfire
Exhaust system failure (exhaust gas leak)
الأسباب المحتملة
Possible Symptoms
Engine Light ON (or Service Engine Soon Warning Light)
الأعراض المحتملة
Description
The Engine Control Module (ECM)/Powertrain Control Module (PCM) detects oxygen content in the exhaust gas by the Air/Fuel Ratio (A/F) Sensor (Sensor 1), and it uses feedback control before the warm up three way catalytic converter (WU-TWC) to bring the air/fuel ratio in the air/fuel mixture close to the target air/fuel ratio. The target air/fuel ratio is adjusted by the secondary heated oxygen sensor (secondary HO2S (sensor 2)) output so that the air/fuel ratio in the WU-TWC to be optimized. When the A/F sensor cannot be able to measure air/fuel ratio in the exhaust gas normally, a gap occurs between the actual air/fuel ratio. As a result, the gap causes a deviation in target air/fuel ratio control (after WU-TWC) which is determined by the secondary HO2 sensor. If the deviation exceeds a limit, the ECM/PCM detects a malfunction and stores a DTC.
