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David H
David H, GM master certified
Category: Chevy
Satisfied Customers: 2668
Experience:  Cadillac Technician 18 years cadillac dealer.ase master certified.gm master certified
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check engine light code 402 fuel running rich

Customer Question

check engine light code 402 fuel running rich
Submitted: 2 years ago.
Category: Chevy
Expert:  David H replied 2 years ago.
Are you sure the trouble code is P0402 I don't show that code?
Customer: replied 2 years ago.
no maybe 420 not sure but it has to do with the catalyct system also replaced oxygen sensor bank 1
Expert:  David H replied 2 years ago.
For a p0420 you will need to replace the catalytic converter will need to be replaced.How have you tested for the engine running rich,usually there would be a code for rich fuel mixture.
Customer: replied 2 years ago.
I replaced the catalytic converter this time last year. how do you check for rich fuel mixture
Expert:  David H replied 2 years ago.
You need a scan tool that reads data.You would look at the fuel trim data both long term and short term.This directly relates to fuel mixture.The fuel trim should be with +10 to -10 of zero.Excessive positive readings like -20 would indicate rich condition.Also any engine misfires would also damage the catalytic converter.
Customer: replied 2 years ago.
how do you correct rich conditions. what type of engine misfires?
Expert:  David H replied 2 years ago.
A rich condition is usually a leaking fuel pressure regulator or leaking injectors.An engine misfire will usually be spark plugs and wires or fuel injectors.
Customer: replied 2 years ago.
The catalytic converter didn't solve my problem, the light came right back on! still stuck!
Expert:  David H replied 2 years ago.
Have the codes been cleared and rechecked since catalytic converter replacement?If so what is the trouble?

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