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Great timing on this thread , my wives truck has been throwing the dreaded po420 code , after replacing all 4 o2 sensors its still throwing the same code ....... I picked up an obd2 to usb cable off of fleabay "should be here today" I hope it helps tracking down what this motor is doing , will report back :]

That's a cat efficiency code, another one that is rarely an o2 sensor, most likely the cat. A quick test is to take an infrared thermometer and check the temp of the pipe going into the cat and the pipe going out there should be at minimum a 50 degree difference with the outgoing temp being higher. If there isn't then the cat is no longer working.

 

Got out the temp gun and did that test yesterday .... temps on both cats  looked good , my test cable came today and I got the included software loaded on my net book, if the rain holds up I will try it out tomorrow :] .

Hopefully this cable will help narrow down the problem ,Also going to do a though intake leak test just to be safe.

 

 

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Great timing on this thread , my wives truck has been throwing the dreaded po420 code , after replacing all 4 o2 sensors its still throwing the same code ....... I picked up an obd2 to usb cable off of fleabay "should be here today" I hope it helps tracking down what this motor is doing , will report back :]

That's a cat efficiency code, another one that is rarely an o2 sensor, most likely the cat. A quick test is to take an infrared thermometer and check the temp of the pipe going into the cat and the pipe going out there should be at minimum a 50 degree difference with the outgoing temp being higher. If there isn't then the cat is no longer working.

 

Got out the temp gun and did that test yesterday .... temps on both cats looked good , my test cable came today and I got the included software loaded on my net book, if the rain holds up I will try it out tomorrow :] .

Hopefully this cable will help narrow down the problem ,Also going to do a though intake leak test just to be safe.

 

You only have to check one side the passenger side. Po420 is for cat bank 1, and its only for the front cat. You really oly need to check 1 sensor which would be the one after the cat on your scanner it would be h02s12, you would need to pull up the info of h02s11 also jus to compare. The front sensors are the actual o2 sensors they are for fuel trim, and when warmed up should be constantly switching voltage, the rear sensors are just monitors for the cats, they should always be a steady voltage right in the middle. It helps if your scanner can graph engine data. Warm it up check data, if sensor 12 is switching at the same or close to same rate of sensor 11 then your cat is not operating anymore. Now you need to figure out why, do you let it idle a lot, that can cause it, or you may have a slight misfire on one of bank 1's cylinders not enough to set a code but enough to let in burnt fuel into the cat which is deadly for them. Ford helps out with that, see if your scanner can do generic obd2 functions for engin test modes. Check mode 6, toward the end (I canst remember the test numbers, your start to see something like this

1 .12

2 0

3 0

4 0

5 0

6 0

7 0

8 0

That's not exact idk what scanner you have but just a guide. What that is though is the misfire moniter test results, and as you can see on my quick little chart cyl 1 has a slight miss, not enough to cause a code but enough to cause cat failure in the long run. Hope this helps.

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