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07 silverado P0420 and P0054 codes. Already replaced o2 sensor and found a bad fuse, still having this issue

James Hau


So iv had this issue for awhile now, at first the check engine light would only come on when it was cold outside, I would clear it and it would be fine till the next temp drop and would never come on during the summer. Last week i changed the fuse and its been fine, but Now it's back, I also changed the 02 sensor. I would say it's just the cat going out and change that but with the p0054 code saying it's the o2 sensor heater that makes me think the cat is fine but I don't know what commands the heater to turn on and what the 02 sensor talks to to say the heater isn't working. I'm really hoping it isn't wiring and it's just some module that is working properly. Idk how it is on trucks but I know on planes you can have a single small fault caused my a single module that controls multiple systems

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11 minutes ago, txab said:

What brand O2 sensor did you install? I'd only install AC Delco or Denso, both are OE. Was the fuse blown prior to replacing? Have you traced out the wiring at all?

I don't remember the brand but I noticed the bad fuse after I installed the new sensor. I haven't shot the wiring cause I feel like it's to intermittent for me to pin down. It worked fine for a week after I replaced the fuse and then it just came back. I'll check the continuity of the heater on the sensor it self Monday but if it's on the Harness side I feel like it will be near impossible to pin down without a doubt.

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I'm assuming we're working on the downstream sensor ...


I always use a test light on the sensor heater circuit. If it can light a light bulb (like a 194 bulb), it can handle the heater load. When you have the light connected, wiggle the harness around to see if voltage (or ground) is dropping out. Pay attention to any wiring that's close to the exhaust - it may have touched and melted through.

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