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Old 06-28-2014, 06:00 PM   #1
bechdan
 
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Unhappy Help and Advice please Code - P0141 and P0420

Hia 2003 Yaris exhaust needed replacing which was done at an ATS garage, straight after we got code P0420 - so took it back and they replaced the Cat with a new one free of charge along with a Bank 1 Sensor 1 O2 sensor.
After this we got codes P0420 and P0141 !!
So I replaced the Bank 1 Sensor 2 which made no difference.

It was due for its MOT so I used a code reader to clear the code temporarily, it passed its emissions test and MOT no problems.

The mechanic suggested that if the code persists it could be an ECU problem, but I doubt this very much as it only happened after the exhaust was changed.

The car runs normally, the main reason I want to sort it is if there is another problem that would cause the EML to come on, we wouldnt know about it!

So....... what should I check next? or is it simply a case of the ECU being fussy about a new Cat and sensors?


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Old 06-28-2014, 07:06 PM   #2
mr_miles
 
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Have you reset the ECU by chance? It may be recognizing a change and not knowing what to do with it?
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Old 06-28-2014, 07:40 PM   #3
bechdan
 
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I havent reset the ECU no, should I try that?
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Old 06-29-2014, 12:10 AM   #4
IllusionX
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If you cleared the codes, and they don't come back... You don't need to do anything.
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Old 06-29-2014, 04:50 AM   #5
bechdan
 
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nope they do come back - hence why im asking on yaris forum ;)
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Old 06-29-2014, 09:09 AM   #6
IllusionX
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P0420 means something is wrong around the cat.

I think your answer is at post 16
http://www.yarisworld.com/forums/sho...0&postcount=16
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Old 06-29-2014, 10:01 AM   #7
bechdan
 
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Thanks but I still dont know what to look at, both O2 sensors are new!

I tried the ECU reset which has now cleared the P0141 code but the P0420 remains.

What do you think I should look at next? Do you think I should try a different O2 sensor?

Edit - is there any way of reprogramming the ECU to ignore this code? Or some other way of fooling it perhaps connecting some of the wires from sensor 1 or 2 to a resistor? Im out of ideas as you can tell

Edit Edit - would it make any difference to swap sensor 1 and sensor 2?

Last edited by bechdan; 06-29-2014 at 10:17 AM.
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Old 06-29-2014, 10:59 AM   #8
IllusionX
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No, it could be a exhaust leak or a/f sensor according to the other thread since you already replaced o2 and cat.
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Old 06-29-2014, 12:00 PM   #9
bechdan
 
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what is an a/f sensor and where is it?
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Old 06-29-2014, 01:42 PM   #10
Rigaud
 
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A/F = air/fuel mixture sensor
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Old 06-29-2014, 02:25 PM   #11
bechdan
 
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Having looked in to it, the first o2 sensor / lambda sensor is also called the A/F sensor on the yaris

http://www.yarisworld.com/forums/showthread.php?t=10760

So im no wiser after your suggestion Im afraid.

Anyone else please give me something to try!
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Old 06-29-2014, 05:23 PM   #12
Rigaud
 
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Here's some litterature to help you out.

Causes

A code P0420 may mean that one or more of the following has happened:

- Leaded fuel was used where unleaded was called for
- A damaged or failed oxygen sensor (HO2S)
- The engine coolant temperature sensor is not working properly
- Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
- Retarded spark timing
- The oxygen sensors in front and behind the converter are reporting too similar of readings
- Leaking fuel injector or high fuel pressure
- Cylinder misfire
- Oil contamination

Possible Solutions

Some suggested steps for troubleshooting a P0420 error code include:

- Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
- Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
- Inspect the downstream heated oxygen sensor (HO2S), replace if necessary
- Replace the catalytic converter

Overall probably the biggest mistake vehicles owners make when they have a P0420 code is to simply replace an oxygen sensor (H02S). It is important to do proper diagnosis so you're not wasting money replacing parts unnecessarily.

We strongly recommend that if you need to replace the catalytic converter that you replace it with an OEM unit. Second choice would be a high-quality replacement part. There are many stories in our forums where folks replaced the cat with a cheaper aftermarket one only to have the code return shortly thereafter.

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.
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Old 06-29-2014, 05:27 PM   #13
Rigaud
 
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O2 sensors can be installed improperly or wires/connector damaged during installation. Sometime while removing or installing an O2 or A/F sensor the mechanic gets the wires in a twist that damages the them.

Make a list or foolow the one here and go by ilimination process. These issues are a real pain in the a** but once you'll succeed it's a good learning experience.

No one touches my cars.
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Old 06-29-2014, 05:29 PM   #14
Rigaud
 
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P0420

http://www.obd-codes.com/p0420

P0141

http://www.obd-codes.com/p0141
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Old 06-29-2014, 06:24 PM   #15
bechdan
 
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I suppose ill check the spark plugs next, its due an oil change now too.
I know its 11yrs old but I dont like giving up.
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Old 06-29-2014, 06:25 PM   #16
Rigaud
 
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Quote:
Originally Posted by bechdan View Post
I suppose ill check the spark plugs next, its due an oil change now too.
I know its 11yrs old but I dont like giving up.
Check your sensors connection at both ends, sometimes it simpler then we think and search for a bigger problem.
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Old 07-15-2014, 05:28 AM   #17
bechdan
 
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Well still at a loss on this one Im afraid, everything is connected correctly and seems to be working normally but still get the 'below threshold' code.
Im just guessing that the ECU doesnt like the new Cat even though its working fine.

Its just a pain that the EML is always on as it wont then alert me to a new fault.
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