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P0420 Error Code

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For quite some time I have been resetting the Check Engine Light on my 2008 Aurion Prodigy. Finally, I purchased an OBD2 scanner and identified the P0420 error code for Bank 1 catalytic convertor efficiency. This is the only error code detected. I am still in the diagnosis/ trial and error process and avoiding replacing unnecessary parts. Google searches have indicated that replacing the O2 sensor is unlikely to fix this error code. Previously, the engine was smoking on startup and the vehicle was purchased with this known issue. Potentially, the catalytic convertor could be oil contaminated or have carbon build up.

I have cleaned both post cat O2 sensors which had a white residue that easily wiped off. Latest bit of research indicates to also look at the long term and short term fuel trim readings. I am assuming that this could point the finger at the pre-cat Air/Fuel sensor/s needing to be cleaned or replaced. I have yet to check for any vacuum or exhaust leaks

My main question is if anyone has had this P0420 or P0430 error code and what ended up being the solution. I am also a novice to using an OBD2 scanner so any advice on how to use it to solve this error code will be appreciated.

Error Code P0420.doc

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The O2 sensor will send readings to the ECU which will then adjust fuel delivery accordingly. Either the O2 sensor is bad or the cat itself, suspect sensor - test sensor before replacing. Depending on the device you could actually monitor the ST/LT fuel trims to see how the engine is running - ie: high trims #'s isn't good, ideally should be close to zero reading. If you have cleared the code & it doesn't return you should be fine.

Edited by ZZT86

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I have very recently cleared the code and waiting for it to reappear to review the freeze frame data especially the fuel trim readings.

In the meantime, I am going to use carby/throttle body cleaner to try and decarbon/clean the catalytic convertor; inspect/clean the air/fuel sensor for bank 2 [because it is easy to access]; swap over the O2 sensors between bank 1 and bank 2 if that is possible; and possibly also try to reset the ECM by disconnecting the battery.

I am assuming that if the error code then appears for bank 2 then it is the O2 sensor and if it still remains for bank 1 then it is most likely the catalytic convertor. Depending upon the fuel trim readings, especially if there is a marked difference between bank 2 and bank 1, then I will have to consider cleaning the air/fuel sensor for bank 1 which is presumably hidden away underneath the air intake body.

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If both O2 sensors are identical then yeah OK. Be careful with the cleanliness of the sensor & threads both in the header/manifold & the sensor itself which could give you grief of another kind.

Your car has done about 200K kms from memory ? I wonder where that sensor is made . . . . good luck.

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As an update, sensors and catalytic convertors do not appear to need to be replaced.

As suggested from an internet search, I used brake fluid around the air/fuel sensor, waited 5 minutes and it came undone quite easily. More troublesome undoing the electrical connection,

I used the carby/throttle body cleaner direct into the throttle body. Afterwards, I noticed a pending code of P0171 so this got me more focussed upon the fuel trim readings and checking for vacuum leaks. Eventually identified the PCV hose connection as the cause and subsequent fuel trim readings look good at idle. Readings for the bank 2 air/fuel sensor are lower/better so now thinking about whether to also clean the bank 1 air/fuel sensor.

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Latest update is that for the past week, I have been recording the OBD2 readings from the freeze frame data, then erasing codes. Code would reappear within a day or 2, so I ended up with readings on 6th, 10th and 11th.

I normally use 91 octane fuel but decided to refill with 98 octane on Saturday 6th and refilled again with 98 octane last night. I think that I may have been trying to eliminate the possibility of engine misfires due to low quality fuel with sulfur content. Picked that thought up from some internet postings about P0420 error codes encountered when using fuel in a US state.  

I was expecting the Check Engine Light to return last night. Earlier this morning, an OBD2 scan revealed P420 as a pending code. I did another OBD2 scan when I got home and for the first time got a green tick indicator on the OBD2 scanner, no error codes. A few more OBD engine cycles must have cleared the pending code. 

A few weeks ago, I put in a bottle of full fuel system treatment so possibly in combination with the 98 fuel, it has cleaned up the spark plugs and maybe the fuel injectors. Hope this is the case. I will keep on monitoring for the next few weeks. 

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Great News CB..I do hope it was cleared

KAA

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Instead of the expensive injector cleaner you could also shove 7-8L of E85 to an almost full tank of 98 (E10 ratio) to clean the fuel system, metho is same only 99% concentrate.

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15 hours ago, ZZT86 said:

Instead of the expensive injector cleaner you could also shove 7-8L of E85 to an almost full tank of 98 (E10 ratio) to clean the fuel system, metho is same only 99% concentrate.

Currently enjoying the 98 octane; engine seems to be running smoother. I have been reviewing my purchase of fuel additives etc. and using 91 RON. Considering using 95 octane unleaded. Past experience with E10 is terrible fuel economy but maybe have to re-consider if it is going to clean the fuel system.

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I don't think that the move up to 95/98 is necessary, your car should run perfectly on 91. I reckon you either got a bad batch of really el-cheapo fuel or the fuel system has become quite dirty after time and all that sludge. Have you ever had the injectors ultrasonically cleaned ? Trying to run quality fuel to clean the system is obviously easiest. I would try half tanks of the best 98 with either a Toyota D4 injector cleaner or 3-4L of str8 E85. Do this several times & then go back to 91 & test.

I'm quite anal about what & where I get my fuel & usually always get the same from the same station.

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I bought this 2008 Prodigy knowing that it had issues caused by neglected servicing. Previously been focused mainly upon getting rid of the engine sludge without removing the front valve cover. Now addressing this error code and finally started to learn to use an OBD2 scanner.

For various reasons, I have been suspecting the fuel injectors and dirty spark plugs. Monday, I did the usual short distance drive and the error code has reappeared. After looking at the freeze frame data, the fuel trim readings are looking much better. Planning upon a longer drive to get the spark plugs up to operating temperature to self-clean.

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Over the last few weeks, the P0420 error code has been reappearing and I have been recording the freeze frame data before erasing the code. What I have noticed is that the high temperature reading for the catalytic convertor has gone up for a few readings to 700C. I did a reading of live data and noticed that the voltage reading for the post cat sensor was fluctuating around the 0.4 range before finally increasing to 0.7 while the voltage for the post cat sensor on bank 2 was steady at 0.7 then it started to fluctuate. I was starting to think that the sensor was faulty or an intermittent poor electrical connection.

In the meantime, I have continued with desludging the engine, bypassed the PCV valve so no oil is sucked into the intake and continued to use 98 RON fuel. Since an overnight trip during the week, the OBD has reset and removed the pending error code [again] so it is back to waiting fo see if the code reappears. 

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well CB you haven't resorted to the big hammer yet so well done..hate the dam intermittent faults..hope your detective work solves it soon for you

keep well

KAA

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Just as well I love a challenge and have learnt [some] patience. Still quite frustrating.

Got a few ideas about the underlying cause so concentrating upon desludging the engine so it does not smoke on startup when reconnecting the vacum line to the PCV valve.

Giving it a few more weeks to confirm the code has now cleared or i am just being further teased before resorting to using sensor spacers.

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