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?
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.
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?
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
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.