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Help? CEL Codes.....

S

SVTRacer

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So i ran my friends code reader through my car when the CEL was on.....this is what popped up:

P0420-Catalyst system efficiency below threshhold (Bank 1)

and

P-430-Catalyst system efficiency below threshhold (Bank 2)


Anyone know what this possibly might mean? im not all into it yet....i'm still learning..


thanks for all who can help!


-Mike
 
Keep in mind that is the problem IS that your catalytic converters are shot (the reason for the 0420, and 0430), that MIL eliminators will remove the CEL from being illuminated, but will NOT remove the possible restriction from within the cats themselves.

If your cats are clogged and failed, you either need to replace them, gut them, get headers, or "live with it" (the clog, decreased exhaust flow, decreased performance).

This is all relevant IF your cats are clogged.. if they are blown out (crumbling and dislodging) them MILS will remove the light and you shouldn't see much decrease in performance.
 
Ray,

The mere presence of the efficiency codes in no way means that the cats are clogged. The fault codes simply means that the chemical reaction needed to cleen the exhaust is no longer taking place.

The presence of any clogging must be established by other means.

Steve
 
Andy Bennett said:
There's also the chance that the lower cat monitors are crusty and not reading correctly.
Click to expand...


Unlikely. The sensors are tested for proper operation prior to execution of the efficiency monitor program.

Likewise, upper sensors won't cause this set of codes. However, running an overly rich mixture due to either faulty upstreams, vaccuum leaks, or misfires WILL cause degradation of the catalyst as the material gets soaked with unburned fuel and looses its capacity to do its job.

Most likely, the cats have degraded and can no longer pass the monitor program's limits. Watching the sensor outputs on a graphing scan tool will show this should the condition be present.

Steve
 
projectSHO89 said:
Ray,

The mere presence of the efficiency codes in no way means that the cats are clogged. The fault codes simply means that the chemical reaction needed to cleen the exhaust is no longer taking place.

The presence of any clogging must be established by other means.

Steve
Click to expand...


Correct.. This is why I mentioned the possibility of clogging OR blowing out. Either could have happened, and both would have removed the ability to be a catalyst to the removal of unburnt fuel/exhaust fumes. In no way would you be able to TELL which condition happened simply from getting those two codes.
 
projectSHO89 said:
.Likewise, upper sensors won't cause this set of codes. ...

Steve
Click to expand...
Incorrect. Lazy upper sensors could cause these codes.

"Determining catalyst efficiency/switch ratio: The upstream HO2S sensors will have a high switch frequency, due to normal closed loop fuel control. With an efficient catalyst, the downstream HO2S will have a low switch frequency. The switch ratio is determined by dividing the number of downstream switches by the number of upstream switches over a given period of time. As the catalyst ages (or if the catalyst is damaged or contaminated), the downstream switches will increase. When the downstream switch rate crosses a threshold value (approximately 0.75 switch ratio), a code is stored (P0420 and/or P0430) and the MIL illuminates"
http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm

If the upper sensors are not up to par, and switching less, the ratio (lower to upper) is increased. At a certain point it triggers the P0420 (and/or P0430) codes. The chances of it happening with a 100% percent efficient precatalytic converter is less. But how many have a 100% efficient precat in this day and age?
 
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Okay...so, after reading all of the responses. this is what im given:

my car is a 1998 black CSVT. it currently has 132,227 miles on it.

dad read all of the responses and he now is leaning towards the Cats being bad.

with that in mind...what would be a price to have this done or get the parts for it??

thanks for any additional help i can get.


-Mike
 
when's the last time the O2s (upstream) were changed? If you don't know then might not be a bad idea to put fresh ones in it. If that doesn;t make the code go away then the cat/s will need to be changed. Even in that case it is good to have good working O2s so it's not like you are throwing money away.
 
SVT for a16 year-old said:
.... it currently has 132,227 miles on it.

dad read all of the responses and he now is leaning towards the Cats being bad.

with that in mind...what would be a price to have this done or get the parts for it??

thanks for any additional help i can get.


-Mike
Click to expand...
At 132K miles, chances are the precats are bad but is it bad enough to clog up the exhaust? Maybe but probably not. If they clogged up the exhaust, you would have other issues too (jerking, missing, bogging, etc.).

Your choices are 1) New precats (about $1500 plus labor $600). Send to a dealer.
2) Mileliminators $30 plus labor. Purchase online and install yourself.
3) New upper O2 sensors (hit or miss) $150 plus labor $250. Any dealer or independent shop can do this.

If it were my car, I'd go for the mileliminators. Well, actually I do have mileliminators (2 years and 43k miles ago). IIRC I installed them at 80K miles at 9.5 years old.
 
Lazy upstreams won't cause these codes. The sensors must pass several tests before the catalyst efficiency monitor is run. Lazy upstreams usually cause P0133/P0153 or P113X/P115X codes.

The Ford OBDII theory manauls available from Ford explain how all the onboard emissions tests are run. It is suggested reading for any one desiring to understand how the tests are run.

Steve
 
projectSHO89 said:
Lazy upstreams won't cause these codes. The sensors must pass several tests before the catalyst efficiency monitor is run. Lazy upstreams usually cause P0133/P0153 or P113X/P115X codes.

The Ford OBDII theory manauls available from Ford explain how all the onboard emissions tests are run. It is suggested reading for any one desiring to understand how the tests are run.

Steve
Click to expand...

As you (and not others) seem to understand how the tests are run, how about tellling us how many switches have to be made by the upper O2 sensors before the cat efficiency monitors are run. Below are some combinations where the P0420/P0430 could happen with the number of switches from the respective O2 sensors.


UpperO2 *LowerO2 *Ratio to cause P0420/P0430 codes

125 * 115 * 0.92
125 * 94 * 0.752
80 * 60 * 0.75
90 * 68 * 0.755556
100 * 75 * 0.75
110 * 83 * 0.754545
120* 90* 0.75
 
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how about tellling us how many switches have to be made by the upper O2 sensors before the cat efficiency monitors are run.
Click to expand...

Irrelevent. That's not how it works. Once the sensors are verified and the Cat Eff monitor runs, a rear-to-front switching ratio of > .75 generally means the cat is dead or dying.

Go to http://www.motorcraftservice.com/vd..._theory_retail&gutsid=diagsheet&menuIndex1=17

Pick a relevent year, in this case, 1998.

See the section on the cat efficiency monitor and the section on the front/rear O2 sensor monitors


Steve
 
projectSHO89 said:
Irrelevent. That's not how it works. Once the sensors are verified and the Cat Eff monitor runs, a rear-to-front switching ratio of > .75 generally means the cat is dead or dying.

Go to http://www.motorcraftservice.com/vd..._theory_retail&gutsid=diagsheet&menuIndex1=17

Pick a relevent year, in this case, 1998.

See the section on the cat efficiency monitor and the section on the front/rear O2 sensor monitors


Steve
Click to expand...
So why is it irrelevant? Upper sensors have to be verified at a certain number of switches to be deemed as functional (or it will register a P0133/P0153 code). So if the upper is deemed functional at let's say 100 switches (and hence no P0133/P0153 code), and if the lower sensor switches 75, then PCM would register a P0420 (or P0430) code.
 
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