Car throwing a code! (PO420)?
Thread Starter
On The Tree
Joined: Jan 2003
Posts: 172
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From: Central MD
Re: Car throwing a code! (PO420)? Basically, thats the code saying your catalytic converter is shot. However, you can reset it with your scanner and see if it comes back. Could have been one time thing. Cats I think are warrantied for 70,000 miles, so its about time they go honestly. I would not expect your O2 sensors to be at fault but it is possible. At your mileage, replacing the front O2 sensors is a great tune-up for better gas mileage. But not neccessary.
Re: Car throwing a code! (PO420)? You need to be sure your O2s are OK. They cost less than a new Cat if your out of warr. I think EPA requires 100K on emission devices such as EGR, O2s and the cat. etc. that is if you bought the car new. I don't think that applies to a used vehicle. You need a scan tool. Compare the pre cat O2 values to the post cat O2 values. The cat is supposed to REDUCE the amplitude of the voltage swing you see on the scan tool when you compare the pre and post cat O2s. Pre cat O2 might swing from 0.100mVDC to 0.900mVDC. Back and forth. The Post cat O2 should be less of a swing if the cat is doing its' job. Say 0.300mVDC to 0.600mVDC. This is ballpark. Every vehicle is different, but there MUST be a reduction in amplitude or you get the REDUCED EFFICIENCY DTC Code like you did. Now you must figure out if the cat is deteriorated or if the O2 itself is failing and the PCM is misinterpreting the sensor value it receives from the O2. Of course you can start swapping out parts, but O2s are a lot cheaper than cats. Then again you can always buy O2 Sims and gut your cats and NEVER have this problem again. It's your call.
Re: Car throwing a code! (PO420)? Man, Thanks for your "detailed" analysis!!!
Here is my thinking.
First, the scan tool is from Auto Zone & does not measure the things you describe.
So basically, it's a crapshoot!
i have purchased the 2 Pre cat 02's & will install them in the morning, reset the SES & drive to work! Approx 85 mi. If no code, i'm good to go. If i throw a code however, i will purchase the post cat 02's.
If that fails, guess i'll get some high flow cat's! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
Thanks again to both of you! Hopefully, the 2 o2's will rectify the problem.
Here is my thinking.
First, the scan tool is from Auto Zone & does not measure the things you describe.
So basically, it's a crapshoot!
i have purchased the 2 Pre cat 02's & will install them in the morning, reset the SES & drive to work! Approx 85 mi. If no code, i'm good to go. If i throw a code however, i will purchase the post cat 02's.
If that fails, guess i'll get some high flow cat's! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
Thanks again to both of you! Hopefully, the 2 o2's will rectify the problem.
Car throwing a code! (PO420)? Hey, my daily driver just rolled over 84K
& it threw this code. PO420 which seems to be one of my O2 sensors. The scanner reads "catylist efficiency below threshold. (Bank 1)???
Which one is this?
Should i replace all of them? Think there are 3?
Is Bosch ok? Was wondering why my mileage was getting so shitty! Car runs fine, just seems to cut out alittle @ higher rpm's. Help me out.
Thanks in advance.
Matt
& it threw this code. PO420 which seems to be one of my O2 sensors. The scanner reads "catylist efficiency below threshold. (Bank 1)???
Which one is this?
Should i replace all of them? Think there are 3?
Is Bosch ok? Was wondering why my mileage was getting so shitty! Car runs fine, just seems to cut out alittle @ higher rpm's. Help me out.
Thanks in advance.
Matt
