Catalyst System Efficiency Below Threshold

[Lisa]

Now that I have solved my semi-working turn signals, I have another problem. My service engine soon light came on and after reading posts on here, I went to AutoZone and had the codes pulled. The two codes were P0420 and P0430. These translate out to Catalyst System Efficiency Below Threshold in bank 1 (P0420) and bank 2 (P0430).

What are the possible causes of this? Is there really an emissions problem (the car recently passed emissions testing) or is a sensor bad? Any good way to tell the difference?

Thanks again for all the help!

Lisa

 

[COliveira95]

Lisa:
Now that I have solved my semi-working turn signals, I have another problem. My service engine soon light came on and after reading posts on here, I went to AutoZone and had the codes pulled. The two codes were P0420 and P0430. These translate out to Catalyst System Efficiency Below Threshold in bank 1 (P0420) and bank 2 (P0430).

What are the possible causes of this? Is there really an emissions problem (the car recently passed emissions testing) or is a sensor bad? Any good way to tell the difference?

Thanks again for all the help!

Lisa

I had this code on my 97 and I had bad cats on my car... I replaced my y-pipe and ditched my third cat and all is well now... a good possibility is your o2 sensors though, maybe your 2 downstream sensors are out of whack..

 

[99V8SHO]

Most likely o2 sensors.

 

[projectSHO89]

It is actually more likely that the pre-cats are dead and that the sensors are fine.

I just went through this exact symptom on a 98 Contour with a 2.5L

Here's a bit of possible good news: Depending on where you live, the pre-cats and main cat are covered by an 8 year/80K mile federally-mandated warranty. My car had 79K miles on it, so I got it repaired free under this specific warranty with the assistance of a cooperative dealer service department.

If you are out of this warranty, you have several options:

1) Replace the precats.

2) Gut the pre-cats, install MIL eliminators, take your chances on your next emissions test.

3) Install aftermarket y-pipe and MIL eliminators (if needed).

4) Install MIL eliminators to get rid of SES, take your chance on next emissions test.

5) Do nothing for now, get rid of car or make a decision before next emissions test.

Notice that the subject of the testing keeps coming up? Under the testing in place here (St Louis), a SES or CEL will automatically cause a failure notice. Newly implemented procedures allow the testing station to simply connect to the OBD-II test connector and scan for codes. If there are no codes, including pending codes, the vehicle automatically passes without ever being run on the dyno while monitoring actual tailpipe emissions.

Steve

 

[SHODWN]

where do you get your info?

Gut yur Pre cats? hahahaha there are no pre-cats. Not on a SHO not on a Contour.

If you mean change your Pre cat sensors, then gut the cats THEN add the MIL eliminators you are correct.

I would swap the front O2 sensors first, if that does not solve it then its time for a Y pipe. The rear o2s just do a limited amount of calibrateing the system. so its highly doubtfull that they are causing the havoc. Have you reset the battery? Try that first (disconnect the battery for a few minutes then reconnect it)

I have Y pipes if you need one..

 

[projectSHO89]

Too much Contour on the mind, not enough Gen III SHO. That's what I get for just looking at the service CD in a hurry.

The Contour V6 has "pre-cats" in the exhaust manifolds, then a main cat after the "Y" junction for a total of three. Those precats tend to die about the time the warranty expires.

The upstream O2 sensors won't cause this error. The downstream sensors can, but probably aren't. I wasted $100 on replacement sensors before a Ford tech told me not to waste my money, the problem was the pre-cats. He was correct.

Steve

 

[Jim Merriman]

Here's one for ya... The V8SHO.com lists the P0430 code as the the downstream O2 sensor for bank 2 below threshold.

Yet on the SHO forum, if you do a search on P0430 - there is a thread from 5.0Stang that says " Well I went by Autozone today and got the 96 SHO "read". I got: DTC P0430 Camshaft Position
Sensor A - Bank 1"

Now that's interesting! Bank 1, hmmm... What's up with that? FWIW, I got a P0430 code today to. I don't thinks it's the cat, or either of the O2 sensors, and the third cat isn't monitored, so what else might cause this code? Are there other issues that are potentially masked by this code.
Thanks

 

[Mr Anonymous]

P0430 is bank 1 catalyst below threshold. So, either the cat isn't doing it's job or the sensor is bad. You can swap the bank 1 & 2 downstream sensor connectors where they're attached to the bracket on the steering rack (plug bank 1 into the bank 2 connector and vice-versa). Clear the codes and drive the car until a the light flips again. If you get the same code, it's a bad sensor, if you get a P0431 its a bad cat.