DPF Filter light came on

[gsmdo]

Hi all,

Not been here in a while, as the convertible is behaving itself... 😆

However, the other day, the DPF light came on, along with a beep.

I dealt with it as I usually do, by taking the car up the three-mile bypass at 70 in fourth gear - an Italian tune-up. This has always worked in the past, but not now... 🤔

So, I bought a bottle of this stuff...

...which arrived this morning. I've put it in the tank, but haven't taken the car out yet.

If it works - huzzah! - but what advice if it doesn't? 🤔

Cheers,

Mike 😎

 

 

 

 

 

[cliffcoggin]

While I am sceptical of these fuel additives, I am open to persuasion by long term results. The treatment may solve a sticking pressure switch in the short term but I question if it can solve the more fundamental problem of the exhaust system being blocked by soot, which is what the DPF switch is telling you.

If the treatment fails to work I understand it is possible to induce an exhaust regeneration with VCDS or similar equipment. Others here may be able to confirm this point.

[Steve Q]

Definitely worth a shot but I'd still recommend a diagnostic check to see if any fault codes flag up for the dpf. You could look at having it professionally cleaned but this may only buy you time. 

[gsmdo]

Thanks. I have a Carly and will give it a scan…👍

[Steve Q]

2 hours ago, gsmdo said:

Thanks. I have a Carly and will give it a scan…👍

Please keep us posted on how you get on 

[gsmdo]

So, I took the convertible out this morning, keeping it in normal performance before it warmed up. After about a mile, I got the flashing glow-plug symbol, and a reduction in power. 🤔

I got to my destination, and switched off. When I restarted, the DPF warning came up, but without the glow-plug lamp, and performance was normal. 

Now up to normal temperatures, I drove it at 70 in fourth gear for about three miles, but on restart, the DPF symbol is still there.

I sat on the driveway with the engine idling, and Carly plugged in. It came up with an odd code - something to do with intermittent signal from the seat belt circuit, and not connected to anything about the engine, so I cleared and rescanned - clean...🤔

I'm going to take it for a spin this afternoon with Carly plugged in to see if anything comes to light. 

I spoke to my mate at Norwich Audi, who tells me that a forced DPF re-gen is £200 - but advised me to shop around. He also mentioned, in passing, that a new DPF was £2,500... 😱

So, I've got it provisionally booked in at CAT Automotive next Friday, for investigation. Their comment was that they need to see why the DPF isn't re-genning on its own, and cure that problem, rather than just addressing the symptom and forcing a re-gen.

I'll keep updating this thread - but please jump in with ideas...

Cheers,

Mike 😎

 

 

 

[Steve Q]

Wowsers that's expensive for a dpf. Definitely worth getting a forced regen and/or get the dpf physically cleaned out. 

[gsmdo]

So, I took the car out for an eight or nine-mile trip today - to get some breakfast...

...which was very pleasant. On the way home, in addition to the DPF light (which had been on from the get-go), I got the flashing glow-plug light, shortly followed by the check engine light. The triumvirate of misery... ☹️

When I got home, I plugged Carly in, and after 20 minutes or so, got the following result:

The Smart Mechanic says:

...and goes on to say...

So, it doesn't tell me much more than the light on the dash. My DPF is clogged and isn't re-genning as it should. No clue as to why... 🤔

It mentions a control unit - anyone know what/where this is please?

Thanks,

Mike 😎

 

[gsmdo]

Well, I delivered it to CAT Automotive yesterday evening, they are looking at it today... 😎

[gsmdo]

So, I've just heard back from the guys at CAT Automotive. They've done a thorough diagnostic and - except for the DPF being blocked - nothing is out of parameters.

CAT had the car to set it up after I had the replacement cam fitted last year. At the time they told me, and repeated today, that the BPW engines are notoriously finicky, and that fitting a non-original cam might throw up problems. In the last few thousand miles, the DPF light has come on maybe twice, but it always responded well to an 'Italian tune-up' and this cleared the light - apart from this time.

So, they are going to clean the DPF, but it seems this may be a feature of using the car going forward...☹️

I'll get the car back on Monday - the total job will be £300. I'll report back when it's back home...

Mike 😎

[cliffcoggin]

Fingers crossed.

[gsmdo]

20 minutes ago, cliffcoggin said:

Fingers crossed.

Indeed... 🤔

[Aspen5121]

On 7/3/2025 at 12:13 AM, gsmdo said:

Hi all,

Not been here in a while, as the convertible is behaving itself... 😆

However, the other day, the DPF light came on, along with a beep.

I dealt with it as I usually do, by taking the car up the three-mile bypass at 70 in fourth gear - an Italian tune-up. This has always worked in the past, but not now... 🤔

So, I bought a bottle of this stuff...

...which arrived this morning. I've put it in the tank, but haven't taken the car out yet.

If it works - huzzah! - but what advice if it doesn't? 🤔

Cheers,

Mike 😎

 

 

 

 

 

Is your fuel gauge working ok? Gauge needs to show at least 1/4 tank or DPF wont trigger. My gauge had an intermittant fault resulting in no DPF regen and car going into limp mode. I replaced the fuel gauge sensor and DPF immediately started.

[gsmdo]

2 minutes ago, Aspen5121 said:

Is your fuel gauge working ok? Gauge needs to show at least 1/4 tank or DPF wont trigger. My gauge had an intermittant fault resulting in no DPF regen and car going into limp mode. I replaced the fuel gauge sensor and DPF immediately started.

Yep - works fine, and the tank is nearly full. Thanks for the tip, though... 🙂

[gsmdo]

OK - I've escalated the situation. 

New gen Audi cam ordered (£780) - I'll have it fitted over the winter. It will pay for itself, if I'm having to pay for DPF regens frequently. 

I love this car, but it does strain that relationship at times... 😂🤣😂

 

[cliffcoggin]

How long did you own the car before changing the camshaft, and did the DPF block in that time?

[gsmdo]

7 minutes ago, cliffcoggin said:

How long did you own the car before changing the camshaft, and did the DPF block in that time?

Six years - and no, it didn't...

🤔

[cliffcoggin]

That seems to confirm it is the new camshaft causing the problem, though I don't understand how or why.

[gsmdo]

On 7/11/2025 at 4:41 PM, cliffcoggin said:

That seems to confirm it is the new camshaft causing the problem, though I don't understand how or why.

Me neither, but as I mentioned, the chaps at CAT Automotive warned me this might happen, because the (very cheap) cam I fitted was possibly not made to work with a DPF - ie it may have varied in lift and dwell from the original. 

He reckoned that the DPW engine was so finicky that it was a poor choice to put a DPF on, although it was a great engine in most other respects...

His predictions came true - hence my plan to return it to a stock cam.

 

Mike 😎