General P0404 EGR code fiat ducato 3.0 160 2008 iveco block.

[Octobox]

Hi I’m new to this forum so hi to everyone. I have an p0404 cade I can’t fathom. The EGR is vacuum operated via a 2 wire solenoid and is operational under power. There is no vacuum leaks and the valve moves freely. The egr galleries are clean and free to flow. When driving with live data on the egr opens around 2k @ 25% and continues to open up to 50% on the flat. Any input would be much appreciated as I’m pulling my hair out with it now. Also how does it know the percentage of open when it is vacuum operated with no potentiometer???

Cheers Octobox

 

[Anthony489]

Hi Octobox

As you say, the EGR is vacuum operated and is open loop, i.e. there is no feedback to the ECU that it has "done what it has been told". I suspect therefore that the percentage figures reported are simply the demand signal sent to the solenoid valve. If the valve is all free moving and the valve, cooler and pipework are clean (and no-one has fitted a blanking plate), it suggests that the EGR valve is not the cause of the P0404 code.

I'm sorry I can't be more specific about the fault code, because there is little or no public domain information on this topic. Fiat are free to assign the generic P0404 code to something slightly different in meaning of their own making.

I suspect that the ECU monitors and processes signals from other sensors such as the MAP and MAF, in order to see if EGR operation is within acceptable limits. Effectively this is an indirect measurement, since the vacuum operated EGR isn't able to be monitored directly. This could lead to a P0404 code being thrown if there was a faulty sensor, or possibly if there was a problem with the throttle body (this also plays a part in EGR operation) though this is more likely to throw a P0638 code. The throttle body is another example of an actuator with no feedback pot (in the Ducato application) and is also operated open loop.

I must stress that the above is based on my surmise, and is offered in the hope that it might shed some light.

 

[Octobox]

Hi Anthony489 thanks for your reply i did wonder if it was measuring pressure difference in the inlet via the MAP sensor. I decided to take it to a mates who has different diagnostic equipment, on the way there i gave it a right good hammering especially on steep hills making it work hard to get the DPF hot. Upon arrival the p0404 had vanished but has now turned into DPF pressure difference code and although appears to be reading fine once turned off and left to settle it still reads 37mbar. I have ordered another so we will see how that goes. Thank you so much for your input you are very knowledgable. ?

If all else fails ill gas axe the iveco block out and weld a 3 bearing 2:1/4 land rover engine in at least with that there is only one wire to go wrong. ?

 

[Octobox]

Hi again Anthony 369 do you know if the throttle body on my 3.0 is only activated on start/stop to stop diesel run on or is it continually controlling the incoming air to make it pull harder on the EGR. The reason i ask is when viewing live data all it does is open and close upon starting and stoping and doesn’t fluctuate on the graph one Iota whilst running. The reason I’m asking is I’m contemplating blanking the EGR but I don’t want it starving of air if the throttle body is trying to regulate it.

Cheers Octobox.

 

[Anthony489]

Hi Octobox. My understanding of the throttle body is that it's mainly (as you say) used under certain operating conditions to reduce the pressure in the inlet manifold and thereby encourage EGR gas flow. It's secondary function is to close when you switch off, to prevent run-on shudder. I would expect you to see some variation in the throttle body demand signal during driving, particularly under light load conditions.

This is another area where "official" information is sketchy, so my experience is based on observations of my 2008 van with the 2.3 engine (Euro 4) which has a catalyst but no DPF.

 

[Octobox]

Hi Anthony thanks for that, i thought it should operate during driving as it has 5 wires going to it suggesting it has a stepper motor and not just a solenoid.

Thanks again Octobox