Code P0420

Tiny
ZORRO9099
  • MEMBER
  • 1998 FORD RANGER
  • 4.0L
  • MANUAL
  • 291,000 MILES
I had code P1131, drove around with it for 3,000 to 4,000 miles with it while figuring it out. Put a new O2 in Bank1 upstream. 1131 code went away, but right after, code p0420 appeared. Cleared it to make sure, but the code reappears, only code now, after about 6-8 trips. This is on a rebuilt engine about 5,000 miles ago, total mileage on truck is 291,000. Is the catalytic converter bad? I noticed the engine running better after the new O2 sensor, and gas mileage improved.
Wednesday, November 25th, 2020 AT 2:12 PM

7 Replies

Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny.

Yes, with that amount of mileage and the condition being set from the prior engines performance I would say it might be time for a new catalytic converter. Here are a few converter tutorials for you to view:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/catalytic-converter-replacement

I've attached picture repair steps below if you want to test. Hope this helps and thanks for using 2CarPros.
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Wednesday, November 25th, 2020 AT 2:37 PM
Tiny
ZORRO9099
  • MEMBER
  • 24 POSTS
There seems to be a direct correlation to my replacing the upstream O2 sensor since 0402 appeared immediately after. What is it about the new 02 causing this? Also, if the catalytic converter is bad, why is only bank 1 catalytic converter being alerted, rather than also getting a 0430 as well?
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Wednesday, November 25th, 2020 AT 6:26 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

I attached the procedure and some pictures for replacing the catalytic converter converter for you.

The easiest way to test is use a scan tool and monitor the rear O2 sensor reading. It should be steady. If it varies up and down the cat is bad.

Roy

REMOVAL
1. Raise the vehicle.
2. Disconnect the downstream heated oxygen sensor electrical connector.
3. Use the oxygen sensor wrench to remove the downstream Heated Oxygen Sensor (HO2S).
4. Remove the muffler and tailpipe.

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5. Remove the three nuts.

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6. Remove the Three-way Catalytic converter (TWC) and the exhaust outlet pipe frame brackets.

NOTE: The exhaust hanger bracket insulators can be reused if they show no signs of damage.

INSTALLATION
1. Install the exhaust converter inlet pipe gasket, the three way catalytic converter and the exhaust outlet pipe frame brackets.

ImageOpen In New TabZoom/Print

2. Install the three nuts.
3. Install the muffler and tailpipe.
4. Lower the vehicle.
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Thursday, November 26th, 2020 AT 4:09 AM
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello again.

Just curious to know the outcome of having your catalytic converter tested. Keep us updated and hope we can still help resolving this issue. Hope this helps and thanks again for using 2CarPros.

Danny-
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Sunday, November 29th, 2020 AT 2:41 PM
Tiny
ZORRO9099
  • MEMBER
  • 24 POSTS
Above it is stated to test the catalytic converter with a scan tool. What type tool are you talking about? A good OBD reader? Do you have the details on doing this test? All I have is a basic reader I believe, but it does show freeze frame data if that matters. I may be able to get access to a better reader/tool if that is what you mean. Other than that, I haven't done much with it yet, as I have been busy. Thanks.
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Sunday, November 29th, 2020 AT 7:06 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You need an advanced scan tool that can read the downstream O2 sensor. You will be looking for a steady volt reading of around.496. It may vary up and down a little.

When the catalytic converter is bad, the downstream sensor will read like the upstream reading from 0 to 1 volt. If it reads that way, the catalytic converter is no good and must be replaced.

Roy
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Monday, November 30th, 2020 AT 1:12 AM
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello again.

As stated in the catalytic converter test tutorial we sent you do you have access to an infrared or thermal test device? If you test the incoming heat into the converter as well as the output heat there should be a difference in temperature. If the heat coming out of the converter is lower in temperature than the inlet temperature then you will know the converter is plugged or malfunctioning. Due to the chemical reaction inside a catalytic converter the outlet temperature will always be higher than the inlet for normal function. Hope this helps and thanks again for using 2CarPros.

Danny-
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Monday, November 30th, 2020 AT 1:13 PM

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