I know that there is a lot of information around about topping up the diesel additive for the earlier C5 models, but I have found it hard to get some definitive information on the later 'X7' version. Here is what I have found and would appreciate any further info!
I have a November 2009 1.6 Hdi 'Airdream' estate (DV6TED4 FAP) which now has the equivalent of 85,000 miles on it. So far it has been a very reliable and comfortable drive, with the only work I have done on the car being replacing the DMF and clutch at 75,000 miles and fixing a broken cable in the driver's window mechanism using a kit off eBay.
Given the mileage I thought that topping up the diesel additive might be a good idea, even though I had yet to see any low level warning coming up, as most documentation says this will need doing at 80,000 miles for the DV6TED4 FAP engine. So I bought the 3 litre kit of the correct fluid from my local dealer. (Infineum F7995, the latest replacement fluid for Eolys 176, to fit systems using a green clickfit on the tank filler.)
I have previously used version 5.02 of Diagbox with this car, and this has always given some rather nonsensical readings for the fluid level. For example, at 56,000 miles it was reporting that there was '102030 ml' of fluid remaining (i.e. 102 litres!!!) with it not being possible to add fluid to the system. No surprise given that the maximum tank capacity is no more than 5 litres! I took this to be a reading error due to a bug in DiagBox, with the correct amount of fluid actually being 1020 ml, i.e. just over a litre. A recent reading showed just over '61960 ml', i.e 619 ml left. This is where things get strange...
I updated my Diagbox to version 7.15 and updated the interface, and this now gave a sensible reading for the fluid remaining (619 ml) confirming my misreading assumption. So I topped up the tank, which took all 3 litres without any over-flow, and go to reset the additive ECU, which to my surprise does not seem to exist!
I assumed that my car would have an additive ECU and that the engine management system on this car was a Bosch 'EDC16C34_DV6', largely because this is the only set-up referred to for my vehicle in the rather poor Service Box documentation, even when searching by VIN. However, it seems that my particular car might well be fitted with some other variation of the EDC16C ECU, but even Diagbox doesn't say which one, only reporting that it has an 'EDC16C' unit with a PSA references of 96.539.589.80 / 96.648.437.80 (I have been unable find any further information on what these references mean.)
I know that other models do use a system where the additive calculation is done by the engine management ECU itself. For example, the 2.2 (DW12TED4) unit, which uses a Bosch EDC16CP39 unit, but as far as I know this is not used on the DV6TED4 FAP motor. I also know that some C4 1.6 Hdi models are also fitted with a multiplexed additive pump that communicates directly with the engine ECU, and so also have no need of a separate additive ECU. Therefore, there is no reason why I had to have an additive ECU fitted.
Back in Diagbox I could find no reference to an additive ECU anywhere, and selecting 'Yes' to the question 'Does this vehicle have an additive ECU?' returned me back to the option selection screen, suggesting that I recheck the configuration of the vehicle. So, I selected the 'No' option and Diagbox reported that the additive level had been successfully reset. So far so good. Then I did a global test to view the new reading and... it is reporting that there are 1820 ml of additive remaining, even though I put in the full 3 litres. (Which Service Box states is the usual service fill volume for the DV6TED4 FAP model.) Despite this the car runs fine, reports no errors and I am sure the system will be happy with thinking that there are nearly 2 litres of additive in the tank for a long while yet.
Another point that might be of relevance here is the rate of consumption of the fluid. In the time I have had the car (according to Diagbox) it has used less than 100 ml of fluid per 10,000 km driven, with the readings also suggesting that the car was filled with much less than 3.5 litres of additive at the factory. In fact, whilst one section of Service Box says that 3.5 litres are added at the factory for the DV6TED4 1.6 Hdi, another page says that the same model is factory filled with 2.45 litres, and the latest models, such as the DV6C (which is essentially the same motor but with 8 valves instead of 16) with just 1.34 litres. (In fact, my additive consumption figures, along with the mileage, only really make sense if it is assumed that my car was also 'filled' with no more than 1.5 litres at the factory). As far as I can make out, the same tank is used for all models.
So questions.
1) Does anyone know what ECU my car might actually have? If it is an 'EDC16C34_DV6', as the Service Box documentation suggests, can it calculate the functions normally dealt with by an additive ECU, or is another variation likely to be fitted?
2) Why didn't Diagbox report that there were 3 litres remaining after the reset? Is this possibly a bug in Diagbox, or is it more likely that for my vehicle the programmed 'service' replenishment volume is actually just 1.8 litres? After all, as time goes on and the FAP system is further refined it does seem that PSA are designing them to run on less and less additive. Alternatively, does some special procedure perhaps need to be followed as with the earlier models? (No mention of this being the case in Service Box.)
Oh! and why is Citroen Service box so poor, being hard to navigate and seemingly missing a lot of relevant information?
Sometimes it seems that running a modern car demands the deductive powers of Sherlock Holmes!
