Obd Ii Dtc P0420
I am getting a code P0420, catalyst efficency below threshold. any clue as to why this code would come up? This is on a '97. 
Supreme Member
Joined: Dec 1999
Posts: 1,237
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From: Reno, NV
Car: yep
Engine: uhuh
Transmission: sure does
Check the rear O2 sensor, it should be a flat reading with little variance, not up and down like a normal one.
The computer thinks the cat is not doing its job, could be the rear O2, or possibly a bad cat.
Is the cat gutted?
The computer thinks the cat is not doing its job, could be the rear O2, or possibly a bad cat.
Is the cat gutted?
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