Question about 2004 GMC Envoy

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O2 Sensor Our check engine light continues to come on and we have been told that our O2 sensors need to be replaced. How difficult is it to replace these sensors?

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Not very, but I own an 04 envoy, same engine light troubles, figured it was the o2 sensor, so I took it to my mechanic to have him tell me which sensor, so I could replace it.  Turns out the sensors are fine, but the secondary air pump is malfunctioning and needs to be replaced.  This is apparently a very common problem with this car, and I would suggest having a diagnostic ran before replacing anything, and besides, if it was an 02 sensor, there are 3 or 4 of them on the envoy and you need to know which one is failing anyway, and only a diagnostic can tell you that.

Posted on Jan 03, 2009


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Posted on Jan 02, 2017


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