Question about Hyundai Santa Fe
If the engine is a V6 (2.7 or 3.5 lit), bank 1 is next to the firewall (right hand) when facing the back of the engine.
If the engine is a 4 cly (I4), there is only one bank and is designated Bank 1 (exhaust manifold).
The catalyst to which the code refers is the UPSTREAM, and there is only ONE upstream cat for any bank.
Clue: Two upstream O2 sensor and two downstream O2 sensors - one before the CAT and one after the CAT. the downstream O2 sensors are identical to their upstream sisters. The only reason for the DOWNstream sensor is to monitor the CAT efficiency (threshold).
The catalyst on either bank is essentially the exhaust manifold which houses the CAT... it is the only CAT to which the code P0421 applies.
Hope that helped
Posted on Feb 08, 2011
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Posted on Jan 02, 2017
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This means the HO2 (Oxygen) Sensor downstream of the catalytic converter on bank 1, is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
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