DPF woes
Author
Discussion

Gareth2061

Original Poster:

2 posts

93 months

Tuesday 31st July 2018
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Hi,

Last week the red engine light came on on my car so I took it to Halfords for a diagnostic check.

They said there were 6 historical errors which they cleared, and which didnt come back, so they said we should be ok. The next day the red engine light comes back on and the car barely makes it yuup a hill. We take it back to the garageand they say its the DPF filer which is causing the issue. they reccomend a cleaner being applied and for me to drive it at 70mph on the mototrway for at least 40 minutes to try and force a clean. The red engine light is still on at this point, and the acceleration is severly effected.

I do as they say and there is no improvement and the light is still on. I take it back to see a different person behind the desk, who seems confused and said that they would need to perform a regen on the DPF in order for the light to come off. They have said this hasnt worked but they are not going to charge me (makes me suspicious) but that I can try and drive on the motorway at 70mph for 40 minutes again to see if it clears itself, meanwhile they will get a quote for the dpf to be sent away for cleaning.

I am now concerned that I shouldnt have followed their advice in the first place and driven it at high speed with the engine warning light on. Does anyone have any experience with this, does it sound like I was given some really bad advice?

My car is a 2012 Nissan Qashqai Ntec+ diesel

Thanks in advance

E-bmw

12,378 posts

176 months

Tuesday 31st July 2018
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Diesels need to be driven at above a certain revs for a certain period of time before they will try to regenerate the DPF.

Dr Doofenshmirtz

16,687 posts

224 months

Tuesday 31st July 2018
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A good thrash down the motorway should do the job unless it's badly clogged.
Modern Diesels need to get hot to do a regen - this will only happen on a longer run.
Halfords probably isn't the best place to go to for advice!

You can buy an OBD reader for a tenner that will read codes and allow you to clear them yourself - cheaper Bluetooth ones for around £3 are just as good, but you need a phone with an app called Torque to do the job.

Bluetooth:
https://www.ebay.co.uk/itm/ELM327-Bluetooth-OBD2-O...

Handheld standalone scanner (easier to use):
https://www.ebay.co.uk/p/U480-Car-Engine-Auto-Faul...

Little Pete

1,844 posts

118 months

Tuesday 31st July 2018
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This is the problem with just reading codes. The code is generally the symptom and not the cause. For example, a DPF pressure sensor fault code doesn’t necessarily mean there is a fault with the sensor, there could be a pressure problem in the DPF!
If there is too much soot in the DPF it will not regenerate. On some vehicles if the fuel level is below a quarter it will not regenerate. Some vehicles will only do a forced regen whilst driving etc.
Find a garage that knows diesels and knows how to read and understand live data.

stevieturbo

17,970 posts

271 months

Tuesday 31st July 2018
quotequote all
Little Pete said:
This is the problem with just reading codes. The code is generally the symptom and not the cause. For example, a DPF pressure sensor fault code doesn’t necessarily mean there is a fault with the sensor, there could be a pressure problem in the DPF!
If there is too much soot in the DPF it will not regenerate. On some vehicles if the fuel level is below a quarter it will not regenerate. Some vehicles will only do a forced regen whilst driving etc.
Find a garage that knows diesels and knows how to read and understand live data.
And that will not be Halfords !! lol

Although "red" engine light adds a little concern...as red tends to mean serious.

Most CEL's are not red ?

Little Pete

1,844 posts

118 months

Tuesday 31st July 2018
quotequote all
If for some reason the DPF can’t regenerate-ash instead of soot accumulation for example-the ecu would log multiple regen attempts that could affect oil quantity and quality. This would make the warning lamp red.
I realise I’m assuming that the fault is DPF related and not some other engine control issue because Halfords said so. laugh

jmcc500

670 posts

242 months

Wednesday 1st August 2018
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Might need to go to a dealer for them to do a static regen. Red light may mean regen inhibited and the derate may prevent you achieving a passive regen. Without sounding rude, have you checked the manual to see what it says?

What were the historic codes? As well as short journeys, other faults can lead to DPF issues, eg a boost leak would lead to high soot and fill the DPF pretty quickly.

chazola

459 posts

181 months

Friday 3rd August 2018
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Lack of power suggests limp mode and/or blocked DPF possibly... is it a car that does a lot of short runs/pootling around town?
Like the others said I'd get the codes read at a Nissan specialist or dealer, worst case scenario is it might be completely blocked with soot and have to come off the car for cleaning/replacing. DPFs are the work of evil...

mighty kitten

431 posts

157 months

Saturday 4th August 2018
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First check with any dpf issue is the pressure differential sensor and the pipe work connecting it to the dpf , seen a few diagnosed as blocked but had a faulty sensor or split rubber hose going to it