[Nick H]

If you're seeing P0400 consistently I'd still concentrate on the EGR valve. Was it a genuine valve that you fitted, and a new one at that? Quite often I've seen either second hand valves or non genuine ones that cause no end of issues.

There isn't a feedback on these EGR valves, so the component that senses and flags the P0400 code is the airflow meter, if the airflow readings don't match the expected values for a given engine speed etc...it flags a fault. If the deviation is small enough that the ECM can't figure where the air is leaking off, it flags 'P2279 air intake leak' fault, however if it's large enough a leak that the control unit can figure it as the EGR, it flags P0400 instead. So in your case it's confidently picking up a large enough deviation of air to throw that DTC.

The -2kpa isn't an unexpected reading either, quite often can show this figure with the car ticking over too. The fuelling isn't adjusted in anyway based off the pressure readings until the actual regeneration process is triggered.

Once the regen is done, if the car is being driven to suit the system (not too many short journeys etc...), the DPF shouldn't be regenerating that quickly at all - so I'd suspect it's physically blocking due to something still going on with that EGR valve. Willing to bet it's relatively sluggish off the mark too.

Also to bear in mind, when you replaced the DPF assembly, did this then get reset in Opcom? The ECM needs to know a new filter is fitted so it can begin a new DPF strategy.

 

[Nick H]

Both P2279 and P0400 are both reported from readings off the airflow meter. So there is definitely an issue whereby the incorrect airflow readings are passing the meter, and highly likely EGR related.

It's common to see these areas sludged up, as they are the channels for EGR passing back into the inlet tract, which meet the incoming air, which will always carry a marginal amount of oil that has been passed back through the engine breather system, depending on how heavily the engine breathes. So you get oily mist meeting exhaust gas/carbon, hence the sludge.

The -2kpa figure would genuinely be of no concern - its an interpretation by the ECM of the voltage coming from the sensor itself. The main thing is that the ECM doesn't adjust fuelling based off this reading until the point where the sensor data indicates a high enough pressure to meet all the criteria for the ECM's DPF strategy and trigger a regeneration.

I'd still say off the back of those codes and DPF symptoms that you have an airflow issue that is causing overfuelling, excess soot being expelled from the engine and premature blocking of the filter, I'd be focusing on that. I certainly have replaced non gen valves before now for issues like this.

 

[Nick H]

A split boost pipe will more than certainly be blocking the DPF prematurely, that's a good find if it's a significant enough split. Could well be the source of all your issues.

 

[Nick H]

Generator lamp is relating to the alternator charge light, and is stored in the ECM as it has control over the charging of the alternator. Unlikely related to the issue however.

The injector deviation figures show how much fuel is being subtracted or added by the ECM to get each cylinder running at exactly the same speed to one another, in your case cyls 1&4 are removing fuel, cyls 2&3 adding fuel. The upper and lower limits for these figures are + or - 1.5mg/stroke, so yours are still within spec.

Depending on the mileage of the car it may be the case that bad spray pattern is causing the noise however, you could try and run something like a forte injector cleaner through the tank, or failing that next logical step would be to have the injectors removed and tested. Is all the service history up to scratch in terms of fuel filter change etc....?

This is all assuming, of course, that the noise is injector/diesel knock related and not something separate.