bankr

I asked this in the Maintenance Forum and it was suggested I do so here.

Error Code 0420

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My car is an LS400 with 120K miles.

The dealer replaced my pan and rear main gaskets. A few days later I got the check engine light and 0420 code. Bank 1 cat, or after cat O2 problem. Dealer says I need a new after cat O2 sensor. Do you think this is my problem? I want to change it myself. Is Denso the one to get? If not, which brand is best, and where is the best price?

The wire goes thru the floor pan and must plug in inside the cabin. Are there any tricks to getting to the plug inside the cabin, like getting under the driver's seat and carpet? I'm getting a little stiff and creaky, hope to be able to do this.

What and where is the best deal on cats?

Any and all advice will be much appreciated.

Thank you.

bankr

LiCelsior

iTrader: (32)

what year? if 1st gen then theres a tut for u!! http://www.lexls.com/tutorials/EFI/m...gensensor.html

bankr

It's a 1999.

Thank you.

bankr

PureDrifter

iTrader: (10)

if it is the o2 sensor gone bad then the basic process is the same.

JBrewster

Your car smoked too much pot.

PureDrifter

iTrader: (10)

lmao, we have the answer!

blkstealthpaid4

I have the same problem on my 95.Don't go waste money on stuff that wouldn't fix your problem.Look up the def. on that code.You and I both have OBDII

kens97sto

You also might check to see that the dealer did not damage the wires or the connector while they were removing the pan.

Ken

bankr

I looked under there today. The wires look ok, it looks like they go thru to the inside on the driver's side of the tunnel. It must plug in under the carpet on the tunnel. How do I get the tunnel covering off?

Thank you.
bankr
'99 LS400

bankr

I had another look under there, the wire loom does go thru the floor pan. I'm having trouble getting the carpet up, it looks like the gas pedal needs to come off and maybe the emergency brake pedal. Any tips on how do do this? Have done Searches and only find stuff on IS sport pedal replacement.

Thank you.

bankr

blkstealthpaid4

I am not sure if you have fixed your problem but I doubt your o2 sensor is bad.I bought a scanner and scanned my check engine problem.I am having 0420 and 0430.It says "Catalyst System Efficiency Below Threshold Bank 1

P0430
Catalyst System Efficiency Below Threshold Bank 2".
If your O2 sesnor was bad it would have given you po155,po135 etc...
My 90 ls 400 I had before was spitting out 21,26,28 and this referrred to the o2 sensor.All I had to do was change the "main" ones on my 1 st gen and viola that fixed it!
After doing research on my 2nd gen ls with the po420 and po 430 I have concluded that I need gaskets in between the exhaust manifold jojnts.This is before and after the cats and there is another one upfront near the "y".
Most shops will tell you to replace the cat and all kind of crapola.When I get in that muffler shop I will tell them what I need them to do and not what they think is wrong with my car.

19psi

an 0430 code usually means the cat is bad. teh after cat 02 sensors are in place to monitor cat efficiency. they do nothing for the driveability of the car.
so if the 02 sensor were faulty, the code would be for the after cat 02 sensor, not for cat. efficiency.
the best way to prevent unnecessary repair is to have the after cat 02 sensor voltage monitored with a factory scan tool. if the cat is operating properly, it will show a pretty flat response. if it's cycling just like the front 02 sensor, the cat is bad.

jz4203

Had a similar situation and switched the rear O2 sensors (drivers side with passengers side), cleared the code and problem has never returned. I was trying to determine if it was an O2 sensor or if the cat was bad, like the dealer said. I've also read about gasket problems right before the rear O2 sensor and was able to "feel" a slight amount of exhaust coming out of the gasket area. Other side was fine. I filled that area with gasket cement (instead of replacing the gasket - fearful of breaking bolts and creating a bigger problem) and everything's fine. So, my total cost was <$5 versus the $1k-2K the dealer wanted to replace the cat(s).

osomoso

Haahahahahaahaahhaahaha.