P0420 diagnosis with tactrix cable

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P0420 diagnosis with tactrix cable

Postby gui67 » Thu Sep 07, 2017 5:55 am

Hello,

My 05 Spec-B has a P0420 code since several weeks.
I tried to datalog with a tactrix cable, hoping to see where the problem comes from, between the front O2 sensors, the cat and the rear O2 sensors, or from somewhere else...

The A/F sensors #1 and #2 are always equal, richens at high load and RPM, stable at 14.7 in cruise. (I think these are the front O2 sensors, could you please confirm?)

The other sensors are called front sensor #1 and #2 in Romraider datalogger but I suspect these are the rear ones, having a value between 0V and 1V, they oscillate nearly at the same frequency and amplitude in cruise.

I also logged A/F correction and learning, but I cannot say from these values what is going wrong.
Here are examples of log:
Image

Image

Are there some other parameters which O should look at?
When I reset the ECU, the Error code will come again sometimes after 10 minutes, sometimes after 4 or 5 days. It depends. I never managed to log the moment where the code appears. Should I try to reset the error and log until the CEL lights?
Or would you have other advices?
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Re: P0420 diagnosis with tactrix cable

Postby jslayz » Thu Sep 07, 2017 9:57 am

Red rear does not seem as sensitive... just looks like it doesnt track with the one in the other bank??
What do the team think
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Thu Sep 07, 2017 2:31 pm

Thanks for your answer
Yes, the red one is sometime a little bit different then the white, it seems like sometimes it does not react so quickly.
Would that be enough to trigger the P0420 code?
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Re: P0420 diagnosis with tactrix cable

Postby jslayz » Thu Sep 07, 2017 11:57 pm

Removing the sensors and measuring the impedance will tell you.

I think in the FSM there are some ohm tolerances listed
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Sun Oct 22, 2017 4:50 pm

I replaced all 4lambda sensors because I though that with 230000km, they have certainly passed the lifetime they were designed for.
I reset the default.
It ran fine for 100km and then the P0420 code comes again.
Hat is also strange is that there is a fuel smell from the exhaust while driving with opened front window. If I smell the exhaust with the engine idling I smell nothing.


But the AFR seems ok while driving, on the datalog.
Could you please confim my assumptions that the sonsors called A/F sensor #1 and #2 are the front ones, the value is AFR. And that the sensors called front sensor #1 and#2 are in fact the rear sensors.
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Re: P0420 diagnosis with tactrix cable

Postby Mariano » Thu Nov 30, 2017 3:44 am

I have same problem now. After replacing headers and front 02 sensor, code started. My problem is bank 1 rear sensor, which is right side one. I was thinking to change bank 1 and 2 sensor positions so I can make sure it is sensor fault. Cats were visibly looking ok and spotless so I dont think thats the problem. Front 02 A/F sensors will fluctuate between 0-1v.
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Re: P0420 diagnosis with tactrix cable

Postby KiDo_Tuning » Wed Dec 06, 2017 6:38 pm

Turn it off in the tune.
Issue is Heater Element wiring loom not the actual sensor.
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Re: P0420 diagnosis with tactrix cable

Postby Mariano » Fri Dec 15, 2017 2:32 am

Flipped sensor positions and still bank 1 code. So not sensor problem. I dont have tune, maybe later. Would 02 spacer take code away? Can wiring loom be fixed?
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Fri Dec 22, 2017 5:10 am

KiDo_Tuning wrote:Turn it off in the tune.
Issue is Heater Element wiring loom not the actual sensor.


I finally removed the P0420 code in the tune.
It was OK for dome time, but not I get P0131...
All 4 sensors are new.

each time I go to high RPM, this error P0131 lights the CEL: (unfortunately the datalog stops when I go WOT... so it is not reaaly visible here)
Image

I also see that at some constant speed, the bank 1 injector PW and AFR oscillate a lot:
Image

Matt, when you say the problem is the heating element loom, do you mean there is a problem in the wire harness of the car? broken wire that gives the power supply to the sensor heater?

Thanks
Guillaume
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Sun Dec 24, 2017 12:15 am

In fact I realized that the problem does not occur during WOT at high RPM but when I release throttle, or even if I downshift at high speed while releasing the throttle, it seems that the ECU activates Over-run Fuel cut, then the AFR goes lean and the error occurs at this moment. maybe one of the AFR sensor goes out of the range with air passing in the exhaust.
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Re: P0420 diagnosis with tactrix cable

Postby Mariano » Sun Dec 24, 2017 7:36 pm

I used O2 sensor spacer and so far no code anymore. I have to drive full tank to see if problem is solved.
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Fri Dec 29, 2017 9:24 am

Did you use the spacer on the front sensors?
I see that the sensor on bank one makes huge oscillations:
Image
these oscillations have an impact on the injector PW during all the drive.

Here is when the error occurred (when AFR goes from 20.33 to 14.7 and stays at 14.7 for the rest of the drive):
Image
it happens when I release the accelerator at high RPM, the ECU goes in over-run fuel cut, so PW=0, AFR goes to the max value and at this moment the error happens. I don't understand why as this is the expected behavior.

Could this mean the sensor is defective? It is brand new, less then 3 month or 1000km... I think I will try the previous one that I replaced because of the P0420 error, but I think is was still OK.
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Sun Dec 31, 2017 12:27 am

OK,
it seems to be a sensor problem.
I replaced the new sensor with the old one and the AFR value is stable, no more iscillations, the CEL does not light anymore.
I hope I can get my money back ,the sensor is not even 2 month old, 1000km... the old one has 230000km.
and it is a Denso, same as original...
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Re: P0420 diagnosis with tactrix cable

Postby Adrian2627 » Sun Dec 31, 2017 8:33 am

Have you checked all the plugs? I know it seems too simple but I had a similar issue with a 3.0 Outback and in the end it was a dodgy loom-side plug causing the problem, and costing me sensors.
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Re: P0420 diagnosis with tactrix cable

Postby gui67 » Sun Dec 31, 2017 10:14 pm

Adrian2627 wrote:Have you checked all the plugs? I know it seems too simple but I had a similar issue with a 3.0 Outback and in the end it was a dodgy loom-side plug causing the problem, and costing me sensors.

Did you have other symptoms, misfire, ...?
I will have a look at that, as I replaced the spark plugs a few month ago, maybe something is not correctly in place. thank you
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