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Old 11-25-2011, 12:47 PM
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Default Oxygen sensor malfunction?

Hi guys, over the past few months I've been trying to find the source of an intermittent P1170 code. Unfortunatly I've been able to find the issue. I've replaced a couple things here and there including the front O2 sensor.

I also bought a ELM 327 bluetooth OBDII connector so I could see some live data from my car to help me locate the problem. Well yesterday I decided to log some data and I've plotted the response from both O2 sensors below:

Click the image to open in full size.
Sorry about the size of the image!

I was hoping some of you around here would be able to tell me if these sensors look like they're functioning normally or if one of them is bad.

And the O2 sensor that was replaced about 4 or so months ago should be the first one (blue line) I believe.
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Old 11-26-2011, 06:25 PM
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Location: Midwest
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Is some one killing the messenger? If the blue line and the red line are of the old and the new sensor than you have proven one thing only: both sensors work perfectly.
The P1170 is most likely caused by a vacuum leak. First place to look is the Air Intake Duct, the rippled section. Bend it to see if there are cracks. If you have any doubt, take it out, clean it well on the outside with soap and water, then wrap some good quality duct tape around it.
Look also at all vacuum lines and connections. Dont forget the PCV hoses and the brake booster hose. The lower intake manifold gasket could be at fault as well.
Listening for the hiss can help too.

Good luck!
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Old 11-26-2011, 10:50 PM
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The Air Intake Duct was actually one of the things I replaced trying to find the source of my problem. It was old and starting to crack. But it's new now so that can't be it. I'll have to look at the other hoses more closely, I'm just not sure of what hose is what in the engine compartment.
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Old 11-27-2011, 01:55 PM
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It is really not that hard.
There are a bunch of pencil sized hoses going going into the intake plenum.

One is for the fuel pressure regulator. Most of the time there are shorter pieces going from a sensor or switch to the final destination.

Another one is for the EGR boost sensor. On the protege the nipple get coked up with carbon and blocks the vacuum signal to the EGR sensor. Poke in there with a strong piece of wire.
You know the PCV hose from the valve cover tot he snorkel.
The brake booster hose goes from the throttle body to the brake booster.

The little hoses are so cheap, you can buy 15 ft and replace them all. Often the hoses get hard and cannot expand and contract enough to keep the seal.

You can also listen for vacuum leaks with a piece of garden hose held to the ear and pointing the other end to various places while the engine runs. A hissing sound will tell the story.

If there are any elbow or t- connectors inspect them closely. they get brittle over time and brake.
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