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Catalytic converter

Tiny
AJVENECIA
  • MEMBER
  • 2007 JEEP PATRIOT
  • 2.4L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
I have a P0420 code on my vehicle. So I replaced the o2 sensors and did a diagnostic. My catalytic converter temperature and o2 sensor are reading as they should, but I am still getting the code for P0420. I have another issue with my car having a rough idle and trouble starting sometimes after refueling. Is it possible that the EVAP system could be causing all the trouble?
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Saturday, November 17th, 2018 AT 11:04 AM

5 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

The 420 code is for a failed catalytic converter. The precious metals are worn out inside and the gases are not being cleaned.

It is never the O2 sensors as they are doing the job of monitoring the catalytic converter.

The way to confirm is to have a scan tool and monitor the voltages of the downstream O2 sensor. It should have a steady reading. If it varies like the front, then the catalytic converter is bad.

Roy

P0420
Descriptor
Catalyst Efficiency (Bank 1)
Probable Causes
Aging or Contaminated Oxygen Sensor (O2S)
Catalytic Converter
Engine Mechanical Condition
Exhaust Gas Leak
Oxygen Sensor (O2S) Wiring and Connectors
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Saturday, November 17th, 2018 AT 11:20 AM
Tiny
AJVENECIA
  • MEMBER
  • 3 POSTS
The o2 sensors are reading as they should and the catalytic converter is reaching proper temperature.
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Saturday, November 17th, 2018 AT 12:44 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
What are the downstream O2 sensors reading when the engine is running?

Can you post a picture of the readings? Are they steady or do they vary in voltage?
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Saturday, November 17th, 2018 AT 1:47 PM
Tiny
AJVENECIA
  • MEMBER
  • 3 POSTS
Upstream sensor varies and downstream stays around.7 volts.
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Saturday, November 17th, 2018 AT 2:25 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Drive it and monitor it and see if it changes.

Also, if you can read freeze frame data from the set code, what was the voltage at the time the code set?

Roy
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Saturday, November 17th, 2018 AT 2:28 PM

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