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2005 Buick Century codes p1404 and p520

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robertmt
User

Nov 9, 2013, 4:26 PM

Post #1 of 4 (3166 views)
2005 Buick Century codes p1404 and p520 Sign In
Please be patient while I explain what I have done with this vehicle. I got a service engine light about a month ago which pointed to the EGR valve. I changed the valve and the light went off for a time. Then I get the light again, I have a code p0171 suggesting O2 sensor. I changed the O2 sensor on the exhaust manifold to no avail. Ordered and replaced the downstream O2 sensor near the Cat and all codes were gone. Success! For a day.

I then find that the water pump is leaking so to gain easy access to the pump, I reposition a large wiring harness and pushed it up toward the windshield while I replaced the pump. After that, everything is fine again, and today we have a strong smell of fuel from under the hood, along with codes P1404 AND P0520. It seemed I may have disturbed some connections somewhere, since these two codes do not seem to be related, but cannot find anything out of place.

After the fuel odor dissipates, the engine runs great, no hesitation, no stalling no shaking. Just the engine light on!

Thanks in advance for any ideas!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 9, 2013, 4:40 PM

Post #2 of 4 (3156 views)
Re: 2005 Buick Century codes p1404 and p520 Sign In
Quote
Then I get the light again, I have a code p0171 suggesting O2 sensor. I changed the O2 sensor on the exhaust manifold to no avail. Ordered and replaced the downstream O2 sensor near the Cat and all codes were gone. Success! For a day.
You're dreaming if you're expecting a downsteam sensor to resolve a P0171. It has absolutely nothing to do with that sensor. It's a lean code.

The P1404 could be due to carbon chunks being broken off and getting caught in the valve.

The P0520 is a problem with the oil pressure sensor circuit.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



robertmt
User

Nov 9, 2013, 4:59 PM

Post #3 of 4 (3151 views)
Re: 2005 Buick Century codes p1404 and p520 Sign In
Well that was my understanding too, but out of desperation I changed the downstream O2 sensor and the light went off!

Thanks for the reply.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 9, 2013, 5:10 PM

Post #4 of 4 (3148 views)
Re: 2005 Buick Century codes p1404 and p520 Sign In
Changing the sensor didn't cause the light to go out. That sensor has one purpose and one purpose only and that is to monitor the efficiency of the Catalyst. It has no relationship to fuel mixture.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.






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