02 Sensor WTF's, CELs, and more

[matmatician]

Hey guys,

Just trying to get this sorted out so I can get an ECU tune. I have the FSwerks header, which means I have 1 02 sensor. This needs to be the upstream sensor, unless i'm mistaken, which my livelink software can't read for some reason right now. The Upstream sensor should be the blue connector, right? Not the grey one? The 02 sensor in the exhaust manifold is plugged into the blue one currently... Here's a pic if I've lost anyone:



I'm getting codes P0135 (o2 sensor heater circuit bank 1 sensor 1) and P0147 (o2 sensor heater circuit bank 1 sensor 3). So, is the upstream sensor bank 2? Tom thinks that the o2 sensor in the exhaust manifold needs to be replaced. Does that sound like a good place to start to all of you? this all is making my brain hurt.

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[BC_ZX3]

The "bank" is referring to the number of cylinder banks. An inline four engine only has a single bank; a V6, V8 or V12 has two banks. So any Focus will only generate DTC codes that refer to bank 1.

[matmatician]

Right, I meant to ask if sensor 1 bank 2 was the one I should be using, and if that corresponds to the blue harness.

[iminhell]

Originally Posted by matmatician

Right, I meant to ask if sensor 1 bank 1 was the one I should be using, and if that corresponds to the blue harness.

Yes you should be using bank 1 sensor 1.
This should be the blue connector.

[matmatician]

It's weird. Im plugged into the blue harness, and bank one sensor 2 is the only one with no cel. The grey harness doesn't even have anything hooked up into it.

[BC_ZX3]

Use the wiring harness colours to confirm the correct sensor.

In the diagram H02S 11 is the first sensor, H02S 12 is the second, H02S 13 is the third as one travels down the exhaust.

[matmatician]

You rock man, I've been looking for this. Chiltons manual doesn't have it. Thanks!

[matmatician]

I'm wondering if maybe when they installed the new engine, they mis-wired it. That maybe they plugged the grey 02 sensor cable into where the blue one should be on the ECU. It doesnt make sense that sensor 2 isnt getting and sensor 1 isnt, when its sensor 2 that should be disconnected. Am I overthinking this?

[matmatician]

Ok, found out there was a burnt 02 sensor extension cable.



Replaced it. Still getting bank 1 sensor 1 CEL (P0135) but bank 1 sensor 2 doesnt have a CEL anymore. *sigh* This is getting frustrating. Help?? Do you think I may need to replace the 02 sensor as well? I have one handy if I do.

[felixthecat]

Originally Posted by matmatician

I'm wondering if maybe when they installed the new engine, they mis-wired it. That maybe they plugged the grey 02 sensor cable into where the blue one should be on the ECU. It doesnt make sense that sensor 2 isnt getting and sensor 1 isnt, when its sensor 2 that should be disconnected. Am I overthinking this?

It would work anyhow. 2 different style of connecters.