Need advice: on O2/Cats/code PO420 (1 Viewer)

[LC96]

HI - I have read through all the threads/posts on the Code PO420, but I am looking for some advice on my current dilema:

1. My very TRUSTED hometown mechanic did a diagnostic check on my 1996 Landcruiser CEL (with the infamous PO420 code!) - and he concluded that I need 2 new cats, gaskets, and front/rear O2 sensors totally around $2500 (ouch!). He indicated that there was no way for him to tell which cat was bad, so both need to be replaced.
1.a. I have seen a lot of posters recommend first replacing the O2 sensors,so.... Q: Can I have him only replace both sensors, while keeping the "bad" cats in place? And then replace the 2 cats separately at a later date if need be?

OR

2. Today I went to big city corner muffler shop who said he can put an "universal" cat on for me. (I plan on having him look at it tomorrow)
2.a. If he confirms that he can do it for me - should I ensure that his "universal" cat is definitely a Magnaflow cat (maybe part number #59956?) and nothing else? I know the upside is lower cost, but what is the down side to installing a non-factory issued cat converter (i.e. could it screw up other parts of my LC?)

Note: My LC currenly has 95,000 miles on it and I have an IL emissions test due next year.

I am not too tech savy, so I really appreciate all the expert advice you guys/gals have to give!

p.s. Can someone also post CruiserDan's parts website as well?

Thanks in Advance!!!

 

[CJF]

Q: Can I have him only replace both sensors, while keeping the "bad" cats in place? And then replace the 2 cats separately at a later date if need be?

Absolutely.

Oh, and Dan's here:

https://forum.ih8mud.com/showpost.php?p=173756&postcount=1

 

[MikePL]

Yup, start with the cheapest option first: replace the O2 sensors.

But make sure you either buy OEM or NGK or Denso (with the right resistance of the heating element). It's been concluded that Bosch O2 sensors usually have a different resistance of the heater and that causes problems (error codes). Do a search on it. There is a lot of info here.

Later on you can proceed with the cats, but before you do that you must ensure that there are no cracks on the exhaust parts before the o2 sensors. This could also falsify the amount of oxygen and fool the sensors causing an error code.

So yes, your mechanic was right when he said changing everything would solve your problems because you would just replace all the system components. But it is much better to pinpoint the faulty elements instead of changing it all.

You know... When you have a flat tire you only repair the tire instead of changing the whole axle, together with shocks. Or when you have a smashed window you replace the glass and not the whole door... you get the idea.

 

[gray]

Extremely unusual for cats to go bad at 91K if it is a stock OEM exhaust;
probably not the cats IMHO.

Do you have any leaks in the exhaust upwind of the cats, or between the two cats?? ie: where the Y-pipe connects to the header, cracks in Y-pipe itself, leaking exhaust gaskets, leak at first 02 sensor port?? These are common causes of a p420 code. If it is a big leak, the cats can get too hot and melt; easy to check the cats; just look inside. Did anyone check the temps of the exhaust system before the cats and the cats themselves with a probe or infrared gun?? Did they check for leaks??

You can do that yourself; first look closely at the exhaust system for cracks, black soot at the connections or at the Y of the Y pipe, etc. Then with the engine cool, have someone start it up then quickly put your hands near the pipes and connections working your way down feeling for exhaust pumping out where it shouldn't pump out; but be careful, it does heat up quickly.

While you are doing that listen closely for any hissing sounds of exhaust gases escaping.

You can also check for any air leaks after the MAF; air intake hose, vacuum hoses,etc.


If you can't figure it out:

1). Get another mechanic. He may be trusted, but it appears he did not properly check out the exhaust system. Remember, he is a businessman, not your buddy.

2) Never go to a muffler shop to diagnose anything unless it is owned by your brother, and you are on good terms with him.

g

 

[LC96]

Update: Had the new sensors put on yesterday - so far so good!

If the light/code rears its ugly head again - I will definitely check for leaks before laying out the big coin for new cats....

THANKS VERY MUCH FOR EVERYONE'S SAGE ADVICE!!!!