Hi all

I am brand new (sort of) to RRS, recently purchasing an L494 SDV6 12-months ago. However, the past few months I've been suffering with a Turbo Overboost issue (P0234-77) which seems to haunt a lot of L494's.

To date I have replaced the throttle body and MAP sensor, but no luck.

This morning I turned the car on and the DPF was almost full (amber warning). So, I obtained a laptop with JLR SDD on it and attempted a force regen etc. and unfortunately instead of the soot level going down, it went up! Started on 28g/l and increased to 30g/l during the regen, so I aborted that. As a consequence, the DPF is completely full (red warning) and in limp mode.

In terms of next step(s), what do people suggest? I was thinking of replacing the oil separator next? As I've read that can be the culprit sometimes ... ?

Any help on this matter would be fantastic

P.S I've attached 2 images of the codes I am getting.

So first problem - are the readings correct?
If they are, I'd be tempted to have someone chemically flush the DPF.
Then you need to find out why it's producing too much soot, which is, at a guess, clogging the MAP sensor and in turn giving an overboost error.
So, Poor combustion - how's the EGR valve? Seems to be a common cause of this sort of issue on the SDV6.

I've always sworn by the various detergents you can run through the fuel system - whether just regular use of 'super' fuels or else the various bottles of additive you can buy. All seek to de-carbon the various parts of the system, pre and post combustion, including EGR and turbo.
I had the SDV6 engine in my last car (Jag XF). Ran it to 127k without any such issues, which I put down to a regular shot of detergents in the fuel.
Given where you're up to - maybe get one of these people out to run a more aggressive dose through?

So, I am potentially thinking about this the wrong-way-around. I was thinking the overboost error (currently unknown) was stopping the regen and subsequently causing the DPF to become full. But it could be, in theory, an issue with the DPF/soot levels causing the MAP sensor to be blocked, and giving me the overboost error instead?

In relation to the below image, this was the state of the MAP sensor when I replaced the throttle body. I replaced the MAP sensor at the same time, so it is likely worth me checking the MAP sensor again? If it is blocked, that could be the cause of the overboost error?

Click image to enlarge

So i"m hesitant to respond as I'm only a hobby mechanic and most of my knowledge is based on the experiences of others as my own SDV6 was pretty much trouble free up until the time (I suspect) the inlet manifolds split and I took the decision to trade it in rather than repair it - hence why I now have an RRS

But, clearly something is pumping something other than air into the inlet manifold. This I suspect is leading to poor combustion and hence the other issues and at the same time clogging up sensors.

So what is it and where does it come from?
EGR issues that cause poor combustion then push more crap back into the system and round we go, so that's certainly one area of investigation. I'd also want to remove the intake pipe off the intercooler. is that full of oil? If so, where's that oil come from? Turbo issues? Is the turbo leaking oil, that gets into the intake, clogs everything up, is burned, clogs up the DPF...?
All theory but yes I suspect the issues you're aware of so far are symptoms rather than the root cause.