[Raidzor]

Alright, this is going to be quite a long troubleshooting description of a DPF, Check Engine and ESP lights, so sit back .
I just replaced the intercooler (which was leaking oil) around 2000km back, when on a morning, right from when I turned the key, the DPF light came on. It then started flashing after about a minute, and then the E-Light and ESP lights came on exactly 20 seconds after that, and the car went into limp mode.
Ordered an OBDII scanner, checked the fault codes, and they came back as P242F and P2458 (screenshot attached). I tried clearing them, and all it did was turn off the E-light and ESP light for 20 seconds (codes also disappeared for the said 20 seconds), but the DPF light kept on flashing. After 20 seconds, limp mode and Christmas tree of lights on the dash again. Most probable cause that came to mind was that since I replaced the intercooler, the oil which was leaking out of it was going into the engine, producing tons of soot and ultimately blocking the already not-so-clean DPF (last time I remember being on a highway was before the repair). Went out, got a full tank
of premium fuel and added a DPF cleaning additive, drove 200km in 6th keeping revs at 2.5k (Catalyst temps from the OBDII reader were above 300C for more than an hour), but absolutely 0 improvement. Which looking back to it, is not too surprising, I had no signs of a blocked DPF in the first place (no smell, loss of power, smoke, rough idle, anything). Came back home, disconnected battery for 15 minutes, and the fault represented itself in the same exact way as it had the first time (video here). I also tried the procedure which worked for me when the DPF light came on in the past (with no E or ESP lights), which is jumping the top right pin on the 6-pin connector to ground and pressing the accelerator pedal 10 times with ignition on, obviously, to no avail. On top of all this, engine is working just as smooth as it was before, no fluctuations in RPM, no smoke, smooth and just great, but with really little power now (by the way clearing the DTCs while engine is running produces a 20 second window of normality). So my best guesses at this point are either a very stubborn ECU that is asking for service or something (this light appeared in between driving cycles, right at the start of the day), or a faulty sensor somewhere. I really want to deal with this myself in the cheapest way possible, since I don't plan on using the car much longer before getting a newer one (we're talking 2006 here), so any tips on even just not fixing it but just turning the damn lights and limp mode off will be greatly appreciated (since I literally can't feel or hear or see even a single thing wrong with the car). Also, just any tips on what sensors to check are also appreciated.Thanks in advance for any answers and thanks for reading into such lengthy description!

 

[Raidzor]

Um, WHY was there oil in the intercooler? It doesnt hold oil, so you need to address THAT first.



UM.... WTF??? Diesel doesnt come in octane grades...

Well, the only source of oil in the intercooler that I can think of is the turbo spitting some. It wasn't pure oil, it was much thinner so it was oil mixed with a bit of condensation. Since my intercooler was cracked, it didn't hold pressure, so it generated a stronger vacuum when letting go of the throttle (a bit counterintuitive here but I hope you understand what I mean) that sucked oil out of the turbine. I have no way of checking if there is oil there or not now that it is sealed and holds pressure properly, but no signs of it really, so I would call it addressed already with the intercooler replacement.

Regarding premium diesel,
there are higher cetane grades, not octane + cleaning additives (mainly nitrogen based) that are in premium diesel fuel here. They do in fact make the engine run a bit smoother by cleaning the injectors a bit and overall having cleaner combustion when you run 2 or 3 full tanks though.

 

[Raidzor]

No, if you have oil in your IC, then you need to address that first... what part of "it doesnt hold oil" is hard to understand? No, vacuum cannot suck oil out of the turbo... a cracked IC doesnt increase the vacuum the engine can pull.

Yes, I understand it is not supposed to have oil in it and I understand that a vacuum should not pull oil out of the turbo. But in my case the failing turbo does indeed spit oil when exposed to vacuum, which ends up in the IC. The vaccuum was stronger with the cracked IC, in my understanding, because instead of pulling the pressurized air (say .3 bar of positive pressure and dropping it to -.1) it was pulling atmospheric pressure down to, say in this case, -.4 bar. I understand that ideally I’d need to address it as it is the root cause, but I do not want to spend on a turbo what would be in my country the amount of money I spent on my car, especially because I am upgrading soon. Anyways, I solved the check engine problem.
Ran the clearing cycle (top right pin in the breaker box short to ground + 2 full throttle presses), but nothing happened. I then disconnected the battery and ran the cycle before the DPF light had a chance to appear. The cycle finished about 80 minutes in and no lights are on the dash anymore .