Subaru Tribeca P0420

Ask for and share advice on using the PicoScope kit to fix vehicles here.
Post Reply
Droidkiller
OneWave
OneWave
Posts: 13
Joined: Sat Oct 15, 2016 3:29 am

Subaru Tribeca P0420

Post by Droidkiller »

Hi all,I have checked O2sensors on Subaru Tribeca B9,6cyl boxer becouse of intermittent P0420in memory.(Cat efficiency below treshold Bank 1.
Pre cat sensor signals exactly the same,but all two bank's post cat sensors signal shows unefficient catalyst system,signal fluctuating by B1S2 and B2S2 too.
My question is,why I don't have P0430,bank 2 DTC,or present trouble code? :?:
Attachments
Subaru_Tribeca B9_2007_pico.psdata
(3.88 MiB) Downloaded 778 times

kona
TwoWaves
TwoWaves
Posts: 66
Joined: Thu Feb 22, 2018 8:14 pm

Re: Subaru Tribeca P0420

Post by kona »

-1- You're reading 1,333 -1,54 V :?:
Proper voltage at the O2 sensor should be .1-.9 volts.

-2- grounding, gaskets leaking ?

Droidkiller
OneWave
OneWave
Posts: 13
Joined: Sat Oct 15, 2016 3:29 am

Re: Subaru Tribeca P0420

Post by Droidkiller »

I've made the measurement with all channel grounded to engine,not the sensor ground.
Thanks for reply to my post

Droidkiller
OneWave
OneWave
Posts: 13
Joined: Sat Oct 15, 2016 3:29 am

Re: Subaru Tribeca P0420

Post by Droidkiller »

Bigger problem for me,if I see blue(bank 1 pre cat),and red(bank 1 post cat),almost mirrored picture,and bank 2 is almost the same with a little more delay.

speck
TwoWaves
TwoWaves
Posts: 63
Joined: Sun Mar 25, 2012 5:20 am

Re: Subaru Tribeca P0420

Post by speck »

Droidkiller wrote:Hi all,I have checked O2sensors on Subaru Tribeca B9,6cyl boxer becouse of intermittent P0420in memory.(Cat efficiency below treshold Bank 1.
Pre cat sensor signals exactly the same,but all two bank's post cat sensors signal shows unefficient catalyst system,signal fluctuating by B1S2 and B2S2 too.
My question is,why I don't have P0430,bank 2 DTC,or present trouble code? :?:
You are looking at AFR sensors

ronw38
TwoWaves
TwoWaves
Posts: 65
Joined: Sun Aug 27, 2017 8:00 am

Re: Subaru Tribeca P0420

Post by ronw38 »

HI Speck is likely right AFR vs 02 . Forget the pre cat measurement and recheck the post cat. Engine temp up - cat temp up 300 deg C + . At steady throttle 1500 > 2000 RPM post cat sensor [standard 4 wire 02 sensor] should read steady on the rich side up to 700mv and be stable - if the signal fluctuates rich/lean you may have a cat problem . As you have two cats the comparison should show any deviation . There are many tests to prove AFR - 02 and cat efficiency but your query is balance between the two . Give it a shot hope it helps. Cheers Ron

Droidkiller
OneWave
OneWave
Posts: 13
Joined: Sat Oct 15, 2016 3:29 am

Re: Subaru Tribeca P0420

Post by Droidkiller »

Thanks guys,I'll check it next time when the car will be here again.

speck
TwoWaves
TwoWaves
Posts: 63
Joined: Sun Mar 25, 2012 5:20 am

Re: Subaru Tribeca P0420

Post by speck »

Droidkiller wrote:Thanks guys,I'll check it next time when the car will be here again.
You can't really check a 4 wire AFR sensor with a scope, provided you own or have a milli. amp clamp.Check them with a scanner, easiest way to do.

AnilS
Newbie
Posts: 3
Joined: Fri Aug 31, 2018 1:42 am

Re: Subaru Tribeca P0420

Post by AnilS »

speck wrote:
Droidkiller wrote:Thanks guys,I'll check it next time when the car will be here again.
You can't really check a 4 wire AFR sensor with a scope, provided you own or have a milli. amp clamp.Check them with a scanner, easiest way to do.


Why cant an AFR be checked with a scope. Thanks.

landroverman1958
OneWave
OneWave
Posts: 43
Joined: Thu Dec 04, 2014 7:53 pm

Re: Subaru Tribeca P0420

Post by landroverman1958 »

The main reason the Afr can,t be checked is because the Afr uses a pumping cell measurement pid in milliamps,so unless you use a £500.00 amp clamp to measure the change in amperage an ordinary low amps clamp is not sensitive as there is too much noise at that low an amperage,you can mulltiply the amperage by wrapping the wire around the amps clamp,but thats not really practical,so normally it is usual to look at the pid for the current consumed by the pumping cell in the Afr.

Post Reply