DPF Frequent Regens - O2 Heated Oxygen Sensor - ECM-P2A0036

[hal9000f]

V70 D3 D5204T7 100 kW MY2013, acquired 14 months ago with 151 kMiles. Now with 161 kMiles. My 3rd Volvo.

My daily commute is 17 miles one way (34 miles daily) and it's mostly motorway (28 miles motorway and only 6 miles in the city). So, it's cushty for DPF. Avg consumption close to 50 mpg UK. Fantastic car :-)

From the beginning I was recording the DPF regens that were occurring between 700 and 1250 miles. Rare, especially in cold weather. No need to say I was very pleased with DPF regen performance.

But, after 11 months DPF regens started to happen more often so it happened 6 times in less than 3 months. While before it occured 8 times in 11 months. Last 3 regens happened roughly every 270 miles. Same avg mileage and car usage all the time. Also, the fuel consumption is now high in the city, but luckily remained low on the motorway.

As I was away on longer trip I couldn't start the investigation sooner. There were no DTC's reported and I was suspecting DPF pressure sensor or its pipes/hoses. So, VIDA only recently (on 21st Sep) reported the following DTC:

ECM-P2A0036 O2 Circuit Range / Performance (Bank 1, Sensor 1).
FM (Frequency Modulated) / PWM (Pulse Width Modulated) Failures.
Signal frequency too low.

Also, since acquiring the car I was collecting data with Car Scanner Pro ELM OBD app and these days it is showing sudden and erratic DPF soot increase as soon as the amount of soot crossed the 9 or 10 grams threshold. When things were good, DPF soot increase was always slow and linear from roughly 5.70 g after regen and up to 25.75 grams which would trigger the regen.

I am attaching some Car Scanner Pro graphs with examples of DPF soot and other parameters. First are when everything was good and others when DPF soot became erratic.

So, please my questions are:

1) is the O2 Heated Oxygen Sensor Front likely to be the (main) culprit?

2) besides the Car Scanner Pro tests for Oxygen sensor which give "Wide Range Voltage and Equivalence ratio" is there another way to test the sensor?

3) what values for the described sensor tests would be normal?

4) could cleaning the sensor or electric connector help or the way is to get a new sensor and that's it, don't waste time trying to clean it?

5) it looks like it's not complicated job to replace it?

6) any other ideas / opinions / hints welcome :-)

Will report back when solved.

Thanks!


Pictures 1 to 3 - DPF soot when all was good.

Pictures 4 to 6 - DPF soot erratic increase.

Picture 7 - example of a DPF regen.

Pictures 8 to 10 - DPF soot erratic and O2 sensor data.

[hal9000f]

Anybody?

Thanks!

[hal9000f]

Installed new BOSCH front O2 sensor 0258017456 (Volvo 9487151), but no cigar :-(

Erased the DTC and during 35 mile ride, wild erratic DPF soot increase still happens.

DTC did not reappear.

Also, much higher fuel consumption during city driving before engine reaches operating temperature.

Any ideas, please?

[37 RUBY]

Hello

Was there an 'adaptation' process in Vida when fitting the new sensor.

Have you looked at live data for all sensors(not just how much soot has accumulated)? Is everything reading as it should including DPF pressure?

[BigGreenThing]

hal9000f,

I have the D3 also (except mines a T2 version from 2011). I've not long past the 160K miles mark.

Once viewing data regularly from OBD - Car Scanner app - DPF regen happens at 25grams or thereabouts and brings it down to about 5-6grams. So all seems good. IT regens when it should (i.e. 25gr) and brings it down to what it should be (i.e. 5gr)

I only use the XC70 for long journeys, the shortest being about the length of your commute.

My regens happen every "few hundred miles" to be honest. As a guestimate, probably every 400 miles (half a tank of fuel's worth). I haven't captured precisely when to see the trend.

I have used premium diesel for some time now in an effort to "clean" (believe what you will about the "hype" on premium fuels)...but I also get 1-2mpg more per gallon with premium. Whichever way (diesel/premium) - it's still expensive!

BUT, codes have been thrown in my instance. Also, no issues with the frequency of regens, no adverse impacts on performance (other than mpg drops when the car is actually going through its regen).

Sorry - I'm not only not answering questions - but instead firing more questions back at you...

Is it worth/ easy to check or change the back O2 sensor (I believe there 2)?

Is the DPF getting hot enough on regen process? What temp are you getting from the Car Scanner app? Mine gets into the 620-720C range when doing a regen.

Could it be that plentiful amounts of carbon exist inside the car at the mileage it's at?

Increased fuel consumption perhaps partly driven by poor injector or injectors?

[37 RUBY]

Hello Admin

The OP is unable to reply to this thread - see below copy and paste of their email describing the issue:

Originally Posted by hal9000f

Hi, thanks for your reply to "DPF Frequent Regens - O2 Heated Oxygen Sensor - ECM-P2A0036".

I am trying to reply (to my post), but get this:

Forbidden - You don't have permission to access /newreply.php?do=postreply&t=335709 on this server.

Will that block eventually clear?

Thanks.

Sasha

[hal9000f]

There was no adaptation required for O2 sensor.

But I did the adaptation of DPF differential pressure sensor and it did not help.

Did some checking with VIDA, but did not catch anything obvious...

I was advised to do a forced DPF regen. Then reset the DPF counter.

Any other thoughts, please?

EDIT: I couldn't post to my own post for a few days, hence the pause.
Will add any news to the story if anything happens...

[Simmy]

a forced re gen is quite a brutal event. not really recommended for people with mechanical sympathy watch some vids on the subject to see if you want this done to your pride an joy

[hal9000f]

Originally Posted by Simmy

a forced re gen is quite a brutal event. not really recommended for people with mechanical sympathy watch some vids on the subject to see if you want this done to your pride an joy

Those are my thoughts exactly

But, some say it's nothing special...Seen one video for V50 and it was pretty mild.... Will look for other videos...

But, what to do next when the mechanic who advised it is experienced...Yeah I am still not convinced that something else is not going on...

I will probably try the new DPF differential pressure sensor first... Got one today for 41 EUR - BOSCH 0 281 006 207.

But, cannot replace it myself cause it's pretty unreachable

So will have to wait at least a week cause they are busy...

[hal9000f]

Originally Posted by Simmy

a forced re gen is quite a brutal event...

Yep, I've seen it on V50, and it was mild event at 2800-3000 rpm.

But, another video with V70 was brutal at 4000 rpm

I bough a new DPF diff pressure sensor and hope it will solve the problem.

But, my mechanic still insists the sensor is not a problem but DPF soot/ash saturation after 150 kMiles or 10 years...

So, now I wait for a vacant term in the workshop...