2005 Hyundai Elantra Q&A

2005 Hyundai Elantra Question: Check engine light comes on

was told rear oxygen sensor needs to be replace but after driving for a while check engine light comes on again. -
Answer 1
So did you have the O2 sensor replaced or just cleared the code? -
Comment 1
Yes. Sensor was replaced. -
Comment 2
And the returned code is the same as before O2 sensor replacement? What code (P----#) is present? -
Comment 3
Replaced sensor with Hyundai part. Code cleared but occasionally code PO420 comes back. -
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