So I am trying to use an Innova 7100 scanner to read some O2 sensor data on my 2006 mazda 3 since it threw a CEL.  It is code P0134.  Basically either a O2 sensor issue, MAF sensor or vac leak.  I want to rule out the O2 sensor to start.

I know the scanner reads and graphs O2 sensor data.  The car has an upstream bank 1 sensor 1 and a bank 1 sensor 2 after the cat.  I can see and graph the down stream sensor B1S2 but it doesn't show an option to graph the B1S1 sensor.

Here are some screen shots of the scanner menu for live data:

Attached File


So am I missing something here?  Does this mean there is no connection to the sensor?  I would have thought it would have at least shown the sensor but no data.  Is that thinking wrong?

I vote use a different scanner.  Wouldn't be the first time they had buggy firmware.

yeah well that I don't have.  I had a cheap bluetooth scan tool but it won't work with an iPhone.

Can't make it to autozone to use their for free?

I can but it isn't just popping around the corner.  40 plus minutes to the closest one.  They let you use a scanner for free?  Never knew that.

I am lucky to drive this car into town once a month.  

Yes, autozone has a free scan tool.  They also have a toolbox of random wrenches and screwdriver and crap.  You can take them out to the parking lot to use for free.  Other tools you can rent and then get all your money back when you bring the tool back.

Its part of their business model.  They sell car parts.  If they give the customer access to the diagnostic tools or hand tools, the customer ends up spending more money on parts from autozone rather than taking the car to a shop.

Its not just autozone.  If you have other auto parts stores that are closer, I would try them to see if they have the free scan tool.

Well even checking with another scanner brand shows the same data as Mine did.  So back to my original question.  

Would this issue show like this if the sensor was bad or is this an issue that could be something like an issue with the wiring harness.  I would have thought that if it were a bad sensor it would at least show the sensor but with no data?

It’s not uncommon to have no data for an aft sensor of that vintage.

Voltage is completely useless. They very in micro amps.



You check the wiring. If it’s good then you replace the sensor.

You’ll have 5 wires. 2 are for your heater circuit. You’ll have a ground, a reference voltage and a signal.

Measure power and ground at the sensor. You should have battery voltage, then you need to unplug the pcm connector. Check for an open in the  signal wiring , a short to Power and a short to ground.


In reality just put a sensor in it.

Yeah but the aft sensor is giving data.  It is the precat sensor at the exhaust head that isn't.  The shop service manual has the trouble shooting matrix to follow and the firsts step is to check the data coming from the sensor then go on to exhaust leak check, vacuum leak check and then maf sensor.  I'll have to check the connection at the harness tie in to see of it is good.  If so maybe I'll just throw a new sensor in.  was trying to avoid just throwing stuff at it especially since the CEL went out two days ago but the scanner still says the code is pending so I expect it to come back on sometime soon.

Well I pulled the O2 sensor today since the CEL code changed on me last week to a damaged or contaminated sensor. Man heat, pb blaster and sensor wrenches were employed with little luck. Finally had to put a hose clamp around the sensor socket since it was flexing too much and slipping. Stopped the threads on the old sensor and had to chase the threads in the exhaust manifold but it all went back together. I hope the next time I do one of these it is easier. They should not look like this when out!

Attached File