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Roy
Roy, import/domestic specialest
Category: Hyundai
Satisfied Customers: 4650
Experience:  ASE master tech for 40 years
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2008 elantra with codes p0171 p0170 p0420 replaced rear o2

Customer Question

2008 elantra with codes p0171 p0170 p0420 replaced rear o2 sensor and pulled out front o2 sensor and looked in converter not pluged
Submitted: 10 months ago.
Category: Hyundai
Expert:  Roy replied 10 months ago.

good morning my name is ***** ***** I will assist

the 420 is a cat code. the cat converter needs to be replaced. the precious metals are worn out and the converter is not doing its job anymore

171 is a lean code. possible causes are vacuum leak, mass air flow flow sensor, pcv valve or low fuel pressure from a bad fuel pump.

Roy

Expert:  Roy replied 10 months ago.

the 170 code is related to the 171 for fuel trim.

Roy

Customer: replied 10 months ago.

anyway to test convertor

Expert:  Roy replied 10 months ago.

you need a real scan tool to monitor the O2 sensors. comparing the 2 wave patterns will confirm. the fact that the code set is a 99.9% chance the cat is bad

Roy

Expert:  Roy replied 10 months ago.

please dont forget to rate me as it is the only way I get paid for my service

Roy