Join Date: Oct 2018
Location: Queensland, Australia
Car: 2.5L 2008 Outback Touring Wagon
Feedback Score: 0 reviews
So, I'm trying to pin down what happens to cause my Outback to throw a P420. A bit of background first:
08 5MT, ~230,000km, purchased in August last year, every service page was dealer-stamped. So far, very happy. I do the minor services like oil+filter changes, fuel additives, coolant flush, etc, but I'll leave the major servicing to the dealer.
I live in Australia about 400 metres above sea level, and most of the driving happens there. Speed limits from 40km/h to 80km/h. It's a 15 minute drive to town at 80km/h, so the car gets to operating temp and I presume it gets to closed-loop mode I use a local fuel depot Premium 95 (I've had problems with their 98, so I avoid it), and the car seems OK using that fuel. I can drive around this altitude for weeks and not have any problems, but on the occasions I have to travel to Brisbane (about 90 minutes' drive), I can just about guarantee the car will throw a P420 error code within 5-10 minutes of hitting the highway (the highway is at sea level).
So, the changes to the cars "normal" life are: increased air pressure (it's enough to make my ears pop slightly when coming down to sea level), slightly increased temperature (it can be anywhere from 2 - 5 degrees C warmer on any given day at sea level), and flooring it in 3rd or 4th to merge with highway traffic at 110km/h.
I use the Bafx dongle and Torque Pro to scan and clear codes, and to watch some of the sensor data. One thing I noted last time I hit the highway and had to stop and clear the P420, was watching the CC temperature afterwards. The external temp along the highway varied from 25 to 28 degrees C, and the indicated temp of the CC was stable up around the high 700s, until the external air temp got to 27 degrees, when the CC temp started to climb and didn't stop until over 900! (That's if I'm reading it right, of course).
Is it possible that the CC, or one of the O2 sensors, could overheat temporarily and mis-read the conditions, leading to the P420, or should I be looking for something else? Torque Pro has a data logging mode, if I use that, what should I look for?
Current- 2.5L 2008 Outback Touring Wagon MT
Previous- 2.5L 1999 Outback Auto