Question about P0420

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Nov 29, 2005 | 06:59 PM

ljb1955

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Driver School Candidate

Joined: Oct 2004

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From: Ohio

Question about OBD2 code P0420 on 99 ES300

Hi, My 99 ES300 has a CEL light. I have an AutoTap scanner and read the code P0420 which is a catalytic efficiency error for bank 1. I am trying to determine if the cat is really bad or if it is an air/fuel sensor problem. I am still a novice with the AutoTap scanner but I have attached the sensor outputs. The one that caught my eye is the "short term fuel trim from bank 1 sensor 2" which is at 99%. I'm pretty sure sensor 2 is the one after the cat. Can someone familiar with this give me some advice?

thanks

Attached Files

99es300.doc (73.5 KB, 216 views)

Last edited by ljb1955; Dec 11, 2005 at 07:42 AM.

Nov 30, 2005 | 05:33 PM

VVT-i

Lexus Champion

Joined: May 2002

Posts: 2,781

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From: Georgia

Welcome to CL. I don't know your Autotap can read the O2 waveform or not, but that what you need to look for. On the 1995-2001 LS400 with V-8 engine if the code shows P0420 or P0430 it's pretty much a bad cat. But on the 99 ES is something that you will need to look deep into before put in a thousand dollars catalys convertor.

Nov 30, 2005 | 05:51 PM

ljb1955

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From: Ohio

Thanks for the reply WT-i. The AutoTap does display O2 waveforms so I'll try and capture them as an attachment. My ES300 still has under 80K so the cat will be covered under warranty. I'm just trying to make sure it is the cat thats bad before I take it to the dealer.

Dec 2, 2005 | 07:40 PM

koolaidman

Lexus Test Driver

Joined: Jul 2005

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From: il

Quote:

Originally Posted by ljb1955

its kinda hard to diag with out a scanner but its possible. if u can get voltage readings from the sensor watch its change .2 to .9v. if it changes drasticly like that
u need a new cat

if it stays at say .3 to .4 -.5v almost a flatline
cat is good

Dec 3, 2005 | 12:52 PM

ljb1955

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From: Ohio

Ok, I captured the waveform from sensor 2 with my AutoTap. I did this at 2500 rpm. Look at the attachment. Does this seem normal? I think this means the catalyst is bad.

Attached Files

O2sensor2.doc (62.5 KB, 216 views)

Dec 3, 2005 | 04:16 PM

koolaidman

Lexus Test Driver

Joined: Jul 2005

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From: il

Quote:

Originally Posted by ljb1955

Ok, I captured the waveform from sensor 2 with my AutoTap. I did this at 2500 rpm. Look at the attachment. Does this seem normal? I think this means the catalyst is bad.

how bout a waveform at idle. in closed loop

Dec 10, 2005 | 10:31 AM

ljb1955

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Joined: Oct 2004

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From: Ohio

OK, here is the attachment showing sensor 2 in a closed loop condition at idle. Also, I finally crawled under the car to look at the sensor and check for exhaust leaks. The sensor looked ok and I could not detect any leaks. I was wondering where the connector for sensor 2 is located in the car? Is it under the seat? It is a 99 ES300.

Thanks again for your replies
Len

Attached Files

O2 bank1 sensor 2 closed loop at idle.doc (60.5 KB, 221 views)