2005 Mazda 6 Computer Diagnostic Oxygen sensor issue

Tiny
ALICEISCOOL
  • MEMBER
  • 2005 MAZDA 6
  • 6 CYL
  • 2WD
  • MANUAL
  • 120,000 MILES
The check engine light came on and my non-dealer mechanic said that P0132 - HO2S11 which I guess is an oxygen sensor issue. My mechanic says he can't fix this computer-diagnosed issue. My dealer is far away. The light has gone off. What is the downside of not having a real diagnosis/repair of this issue?
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Tuesday, January 6th, 2015 AT 3:31 PM

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Tiny
CARADIODOC
  • EXPERT
The good news is the first step is to read and record the diagnostic fault codes, which was done. The second good thing is you appear to understand that fault codes never say to replace parts or that they're bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition.

P0132 - Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 1)

This code could suggest the sensor is working properly but it's reporting an unacceptable condition, although that code would typically be "running too lean too long", or "running too rich too long". A more likely suspect is the 12 volt heater circuit is shorted to the signal wire. That can happen inside the oxygen sensor but more often it's due to the wiring harness falling down and wires melt together on hot exhaust parts, or there's corrosion between multiple terminals in the connector.

The Check Engine light turned on because the fault code refers to something that could adversely affect emissions. The fact the light went out at times means the problem is intermittent and doesn't act up all the time. That would make the sensor itself less suspicious.

The problem with ignoring a Check Engine light, even one that goes off intermittently, is when it comes on again, you won't know if it's the same recurring problem or a new one that could be very minor, but turn into an expensive one if ignored. If you have a simple code reader, you can check the codes periodically to see if any new ones were set. You must also understand that when a code sets, there are a number of other self-tests that will be aborted. In this case the Engine Computer occasionally forces a too-rich or too-lean condition to see how the other sensors respond. When it has a fault code for an oxygen sensor, it stops running any test that needs the results of that sensor to interpret how the engine is performing. There could be other, new problems that develop but don't get detected, that is, until the oxygen sensor problem is fixed. Then the aborted self-tests will resume and new problems will be detected. That is very frustrating for owners and mechanics. It happens most often when the first problem is ignored for a long time. The mechanic has to go by the fault codes currently in memory to give you a reasonable estimate for diagnosis and repair. Once you approve the repairs and they're completed, he finds out for the first time there are other problems, and he has to tell you more diagnosis and repairs are needed. We hate having to do that.
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Tuesday, January 6th, 2015 AT 4:02 PM

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