Check Engine light on, V40 D2

[rx6180]

Hi.

I bought my 65 plate V40 Cross Country D2 in July 2019 with just under 17,000 miles on it. Approximately mid way through September the 'Check Engine' light winked on while waiting at a roundabout, and stayed on. The car performed fine. I was just within my 3 month used car dealership warranty period, so they had it back for a day and a bit, and they said it was a sooted up oxygen sensor, they cleaned it and reset the fault code. All was fine until I was coming back from a family visit on Christmas Day, a 20 mile trip on the M1, and the 'Check Engine' light winked on again. Just like before, no change in vehicle performance, no other warnings, just the 'Check Engine' light. So I suspected the sensor sooted up again.

As I had threatened to buy my own diagnostic tool before, but hadn't, this time I've bought a Foxwell NT301 for just under £70. The fault code is P049D, and the scanner says 'check vehicle handbook'! This forum worried me with a thread about expensive EGR valve troubles linked to the P049D code, on the D4, but a contributor said "If it's a D2, it's an oxygen sensor". Which concurs with the dealer diagnosis last September.

I cleared the code, with the Foxwell tool, but was left with a 'pending' code. I'm new to this, so had to Google the exact meaning, but I get what it means now. The 'fault' had not yet cleared the vehicle's self diagnostic test.

I went for a 20 mile drive, all was fine.

The 'Check Engine' light came back on two days later.

So here are my questions.

1/ Because of work this week and dark evenings, I've not tried to find the front O2 sensor yet. Is it accessible from under the bonnet, or do I have to get the car in the air?

2/ If I take the sensor off, do I need a new gasket or washer to refit it?

3/ I've seen YouTube videos of spray can carburettor cleaner, soaking in injector treatment fluid, or even soaking in petrol to clean O2 sensors. Any opinions?

4/ Finally, my daily commute is about six miles each way, and I admit in the winter months I've not done much motorway driving, though the 'Check Engine' light came on in September after several long fast trips. And I only use Supreme Diesel. So why does the O2 sensor soot up? Car has now done about 20,600 miles.

I previously had a C30 with the 1.6 Ford/PSA engine and though the dpf failed at 60,000 miles, I never once had the 'Check Engine' light on in 30,000 miles of driving. And I could tell when the C30 was doing a dpf regen as I could hear the engine fan, the fan would run on if the car was stopped during a regen, and the 'miles to empty tank' display would drop significantly during a regen. Plus 'Stop-Start' would disable.

The V40 D2 gives few if any clues. The fan is too quiet to hear. If it is running, it cuts out when you turn off the engine (I know from looking under the bonnet). The 'miles to empty tank' readout is all over the place on a daily commute, and the 'Stop-Start' isn't working half the time anyway during winter commutes. I wish manufacturers would install a simple warning lamp to tell the driver the car is attempting a dpf regen, so we could modify our journey and driving to allow the cycle to complete, but instead they prioritise the dpf regen being 'automatic' while you drive. Consequently if you don't know what the car needs to do, and normal journeys do not permit a dpf regen, the particulate filter clogs up and diesels get a bad name. All of which may have nothing to do with my oxygen sensor, and anyway I've taken to looking under the bonnet with the engine running to check to see if the cooling fan is operating if I suspect a dpf regen is underway while I'm pootling around town.

If Volvo allow the V40 D2 to do a regen without the electric cooling fan needing to run, them I'm stuffed.