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Codes P0135, P0301 and P0404

Tiny
MASTEROFDISASTER
  • MEMBER
  • 1997 CADILLAC DEVILLE CONCOURS
  • V8
  • 84,000 MILES
Failed emission test with codes p0135, p0301 and p0404. What parts do I need to replace and where are they located? I think EGR is one of those. Thanks, rg
Monday, July 29th, 2019 AT 2:03 PM

3 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

In the diagrams down below I have included the factory diagnostic troubleshooting guides for Direct Trouble Codes(DTC)(s) P0135, P0301, and P0404 for your vehicle. Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Wednesday, July 31st, 2019 AT 8:14 AM
Tiny
MASTEROFDISASTER
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  • 4 POSTS
Thanks Alex.
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Wednesday, July 31st, 2019 AT 9:49 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
I would start with the 02 sensor replacement

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

This guide will walk you through the steps.

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

First sensor on bank 1 - Please let us know what happens.
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Friday, August 2nd, 2019 AT 3:57 PM

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