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Discussion Starter #1
This is for my ‘02 Mustang GT.

I’m having some troubles with both O2 sensors (P0141, P0161 and P0156). I have installed new Motorcraft O2 sensors and get the same codes. The sensor wires and connectors look good.

The 141 and 161 problem is probably the heater circuit fuse. Does anyone know where that fuse is? I can’t find it on any diagram. I changed fuse #8 (20A) under the dash thinking that the description, ‘Engine Controls’ might be it, but I still got all three codes.

I‘ll look for an exhaust leak on the 156 code later.

Thanks!
 

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02 codes does NOT mean replace 02s

its a circuit issue

you have to test the circuit, find the open or short
 

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Discussion Starter #3
Yes. That’s my next step. I’m wondering if there is a fuse and which one it is.

we just moved to Tennessee and my Ford manual is lost In some box. I cant find an online wiring diagram, either.
 

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Discussion Starter #4
Also, I tested both old sensors. Multimeter leads on the black lines and got ‘1.’ So, the sensors were bad.
 

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Discussion Starter #6
I don’t know. I rarely do anything electrical and have to relearn this Electrical/continuity topic every few years.

Open circuit, or 1.0 as my meter displays, means electricity will not flow in the heater circuit. So, the heater portion of both of these O2 sensors can‘t function.

Since, all I was doing was a continuity test, I would have received a ‘0’ if I had continuity and would have moved on to testing if I received power to the sensor.

i was hoping not to have multiple problems. But, dang!

please let me know if I’m missing something. I am still trying to find out which fuse(s) are in the O2 sensor lines.
 

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Discussion Starter #8
Open Line? Yes....... No continuity, no connection, heating element won’t heat, busted.

yes, but only 50.1%
 

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Discussion Starter #10
Check out this YouTube video. Go to 1:20. I did my test the same way Chris Fix did. My meter is similar to his.


Hope this helps.
 

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I would clamp and measure the amp draw

I will assume you heater is open then
 

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Discussion Starter #12
Both heaters, yes.

I really want to check whichever fuse protects the circuit.

There are several things I want to do under the car. So, I’ll put it on four jack stands the next time I work on this. I can check each wire’s voltage and run down any problem.

This is an interesting drawing. The HEGO is a heated exhaust gas oxygen sensor. The wire bundles lead to the under-hood fuse box.

1061811
 

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Discussion Starter #14
Like I said in post #3, I can’t find my repair manual. I would have made quick work of this a few days ago, if I had my book. Argh!
 
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