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Catalyst efficiency Low, Below threshold?

Tiny
LOLO
  • MEMBER
  • 1998 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 117,396 MILES
My 1998 Chevy Tahoe have the Check engine Light on. I used my Global OBD 2 code Scanner. The lecture said: Catalyst efficiency Low, Below threshold.
The Tahoe runs good. What the problem? Do I have to replace the catalyst comverter?
Tuesday, May 20th, 2008 AT 7:05 PM

1 Reply

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

The code:
P0420 Catalyst System Low Efficiency Bank 1

This could be triggered due to few factors. It can be due to a bad catalytic converter. It can also be for a leak in the system, also can be a bad oxygen sensor.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor
https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
https://www.2carpros.com/articles/catalytic-converter-replacement

I have attached the step by step diagnostics, it can help determine the cause.

Please let me know of any questions.
Thank you.
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Saturday, September 18th, 2021 AT 12:18 PM

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