Check engine light, code P0420

Tiny
CHARLIETACOS
  • MEMBER
  • 2010 SUBARU IMPREZA
  • 2.5L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 190,000 MILES
There is an exhaust leak on the car, it is audible driving at 5-10 mph or 65 mph next to a wall.

Check engine light returns P0420. O2 Sensor 1 reads 2.2-2.7V and O2 Sensor 2 fluctuates greatly.

Question: can the exhaust leak causes both O2 sensor to return such results?

Is my O2 sensor faculty? Is my catalytic converter bad?

Thanks.
Sunday, June 16th, 2019 AT 12:19 PM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good afternoon,

The sensor is reading correctly.

When the rear sensor fluctuates, it is indicating the cat is not doing its job.

I would have the exhaust leak repaired first and then check the readings again. If they are the same then It needs a new catalytic converter.

Roy
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Sunday, June 16th, 2019 AT 3:04 PM

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