club.liberty.asn.au

Ric wrote:I'm occasionally getting P0420 codes thrown in my manual 3.0RB.
It only happens when on cruise control doing about 80 on a freeway.
All my reading points to an O2 sensor, but I'm not sure if it's one or both of the front sensors, are maybe the rear.
Subaru suggest it's a failed cat, which they are happy to replace for only $5,000

I have a Bluetooth OBD2 interface, and Torque-free installed on my Android phone.
I think by logging the O2 sensors, I should be able to establish if they are the problem.
Only a few of the O2 sensors listed by Torque actually seem to give a reading.
Can anyone advise precisely which PIDs I should be watching, and what for?

Kekotic wrote:Ric FYI Matt disables this code on his tunes because it is basically for emissions on the rear cat and doesn't do anything.

jakey wrote:

Kekotic wrote:Ric FYI Matt disables this code on his tunes because it is basically for emissions on the rear cat and doesn't do anything.

Kekotic wrote:

jakey wrote:

Kekotic wrote:Ric FYI Matt disables this code on his tunes because it is basically for emissions on the rear cat and doesn't do anything.

S Hat Icture F Arth?

jakey wrote:Es. Ad arth.

KiDo_Tuning wrote:It is the rear O2 sensor detecting higher than normal Exhaust Gas Temps based on closed loop feedback from the Heater circuit. ECU assumes that your cat has failed and thus throws code. It is easily turned off, even if you don't want a tune or have an existing tune

Ric wrote:

KiDo_Tuning wrote:It is the rear O2 sensor detecting higher than normal Exhaust Gas Temps based on closed loop feedback from the Heater circuit. ECU assumes that your cat has failed and thus throws code. It is easily turned off, even if you don't want a tune or have an existing tune

Thanks Matt.
I may well get the code disabled soon, but I would like to identify the root cause first.
Do you think I can establish that by logging all the sensors? I can only find two that appear to be active in Torque.
Alternatively, do you think one of your tunes would clear it up anyway, even without disabling the code?

Ric wrote:Thanks.
So is it in fact the Cat slowing dropping off in efficiency, or a sensor dying that causes these errors to start appearing?
From my research, it's triggered by a lack of difference between the front and rear readings (which a bad cat would cause), but can also be triggered by a slow responding front sensor.
My car has done 188,000 km, with a stock tune the whole time.
(Although to be pedantic, the engine was replaced at about 28,000k, so it has only done 160,000)
I usually run Shell-95, with an occasional tank of Optimax, or the BP/Caltex equivalent