Po420 Code, Low Efficiency In Catalyst System

[nelson]

Hi Folks,

I got a check engine light and here's the code I'm getting...

PO420 - "Catalyst System Efficiency Below Threshold - Bank 1"

I have a friend who works in a Lexus service department. He says their line would be for me to replace oxygen sensors to see if that fixes it. If not he says they would then recommend I replace the catalytic converter. I won't let no dealer do the work. But at any rate I just don't want to spend that kind of money on the emissions system.

Does anyone have any experience with this? Do I have any alternatives or am I going to have to keep staring at this dern light?

Thanks,

Nelson

[Thi]

According to the diagnostic procedure and explanation that I read, there are O2 sensors; one infront of the catalytic converter (CC) and one behind it. The wave forms from the 2 sensors are compared by the ECU in order to flag the code P0420.

You need to check the two O2 sensors. Disconnect the connector from the O2 sensor and check the resistance between between terminals +B and HT of the sensor; it should be around 11 - 16 ohm at 20°C (68°F). If they are not in spec, you may need to replace them. If they are good, your catalytic converter may be bad.

Thi

[nelson]

Thanks, Thi.

I will check it out hopefully sometime this week and report the results.

[2GZ]

what's up? ok, back to the basics. there are 2 sets of sensors in the exhaust system, in the front you have the actual o2 sensors and after the cat you have the monitors if you will, when the so called tech checks his scanner he can read and compair the two sensors. if the sensors are switching at the same rate the cat is shot, if the o2 sensors switch fast and the monitors switch slow the cat is fine and the result would be a bad sensor.by the way..i would only have the dealer install the parts .... atleast they stand behind their work

[nelson]

Thanks, 2GZ. This is good info, I am thankful for the forums.

It would be nice to have someone else do the work... someone who stands behind it. But my buddy says the dealer here in Virginia Beach would charge $600 to replace the sensors, which they would do first, and over $1k to change the catalytic converter, which they would do if replacing the sensors didn't work.

That's a bit high. If I were going to spend $600 to possibly $1600 on the emissions, it woudln't be for a repair back to factory condition.

[2GZ]

your welcome. however, you still say "the dealer will determine if the car is fixed a/after/ the sensors are replaced.....that is not acceptable! they are to be schooled and knowledgeable enough to tell you what will and will not fix the car the first time!!!!! go to another dealer., or ask for another tech.

[giggleau]

Hi,

When I was driving my 1996 lx450 the other day, the check engine light turned on. I went to Toyota dealer, they told me the code p0420 -CATALYTIC CONVERTER BELOW THRESHOLD. CAT needs to be replaces. The price is &760

I read the information posted here. But I still don't know how to deal with it. Did you get it replaced or not? Is this going to affect the engine?

Thanks

[dougjohn2]

CAT needs to be replaced or O2 sensor(s) need to be replaced?

$760 seems high to repace a sensor or two, but WAY low for CAT replacement.

[giggleau]

I'm not quite sure which parts they are going to replace.

The paper says "CAT needs to be replaced". I"ll call on Monday to

find out.

I know CAT is part of the exhaust system. Is it urgent to replace it or it is not?

Does it affect the engine system?

Since it is really cold here, I'm going to wait until the weather gets better.

CAT needs to be replaced or O2 sensor(s) need to be replaced?

$760 seems high to repace a sensor or two, but WAY low for CAT replacement.

←

[dougjohn2]

the CAT is the catalytic converter. On your 450 its the two bulbous things right under the passenger floor board attached to the exhaust system. They're right before the muffler.

Urgent to replace? Don't know. Do you have smog/emissions testing in IA? If not, then there might be no rush. If it's clogged, you might get poor engine performance or poor fuel economy...or...you could have no problems at all. Cats are strange that way.

Find out everything they want to do.

[giggleau]

I called the dealer today. He told me that it is the CAT (the catalytic converter) that needs to be replaced. Actually, when I eas driving my car, I didn't feel anything abnormal.

Thanks

[dougjohn2]

If you can get the catalytic converter replaced for less than $800, then I think you should do it. I've read that these normally run around $2000.

I won't necessarily second guess what the mechanic is telling you.

[giggleau]

Thank you very much, dougjohn2. I'll think of it. Actually, it was a bad experience.

I got a car accident the other day, the front bumper got a breach gap ( 2 inches). My turning signal light was broken. It'll cost me $1000. The next day, the check engine light turned on. I thought it might be caused by the accident. But it seems not. They just happened to occur at the same time.

[Nomis]

Here's a tidbit of info that saved me quite a bit of $$$. If your vehicle is under 80,000 miles and the cat fails - the manufacturer is required to flip the bill for a brand new unit plus labor. I had mine replaced at 76K by the local Lexus dealer and I didn't pay a dime. This is a Federal regulation - so it is applicable to every state in the union.