Assich, on mine there are three control units in the main box; the engine ecu, the suspension ecu and the abs ecu. The suspension one is the one with two connectors to it, I seem to recall that the larger of the other two is the engine ecu - but I may be wrong.

There is another control unit in a separate container on the front of the main box, that one is for the cruise control.

Derek

Assich,
The computer for the autobox is bolted onto the box. The other separate 'container' is as I mentioned before, the ABS hydraulic control unit. The ABS computer is in the black box.

Just got the results back from a dignostic reading I had done. I asked the Citroen Garage if they new if I had the latest software for the gearbox installed. They said they would need to connect it up to the diagnostics machine. My ABS has been playing up too so I thought I may as well. The report back was that the engine speed sensor has gone. This surely must be used by the engine ecu when talking to the gearbox ecu and may well solve my "rough" change between 2nd and 3rd that I get from time to time and the problem with dropping into 1st just as I accelerate again. Heres hoping. Now I will place seperate post for it but may as well ask here too. I can see the connector for the speed sensor below the inlet to the manifold but it obviously has a flying lead to the actual sensor. Anyone know where the sensor is actually mounted? Anyone else had this come up on the diagnostics?

On top of the 4HP20 autobox there is a small (20-25mm I think) round gubbins in a rather fetching shade of metallic blue. It has nine small lugs equispaced around its periphery and has a flat top which bears the legend:

DURN
0501314 809
PA66-H

It's free to turn against slight resistance in either direction, but can be neither lifted nor depressed. It's immediately outboard of the selector input, in front of the oil cooler.

I hoped it was a dipstick but it looks unlikely. Does anyone have any idea what it is? And have I done any damage by rotating it?

Cheers, all

Derek

Hi Derek,

As promised I've had a look at the Citroen manual for the 4HP20 but can't identify which part you're referring to. Any chance of a photo?

Cheers

Roy

If this works ( first time I've used it), this should be a photo of the blue thingy.

Derek

I have finally replaced the engine speed sensor on the car and the gearbox is now smooth as anything. I can't really feel the changes, just see them on the rev counter. Well worth checking on the diagnostics if your gearbox doesn't change as smoothly as you would expect. It doesn't light up the check engine light if it goes so you don't know.

My "blue thingy" turns out to be the gearbox breather and it is removable and is used for filling the box on cars without a dipstick. So we now know the whereabouts of the drain plug, the level plug and the filler plug. All we need now is a source of the correct oil, Esso LT71141, my local Esso garage has never heard of it.. And even when you go through the full procedure you change less than half the oil.

Not a satisfactory engineering solution. Ce la vie.

Derek

Hi Derek.

If you're in Lincs and they're handy, bimble along to the Land Rover bit of Rimmers and ask for STC 4863. --- 1 ltr of LT71141. Any decent LR place should recognise the number.

Mike.

Thanks Mike, I'll try that.

Derek

Can't you adaptive guys just use Amsoil synthetic ATF and solve all your compatible fluid problems?

It's superb stuff and it's universal.

The only problem is that it's £50 for 5 litres but I have it in my 4HP18 and it's super. Many of my friends use it in their Mitsubishi tiptronic boxes (design licensed from Porsche) and all reports are brilliant.

Today I added RX Auto to my gearbox which is supposed to help clean it over the next 1500 miles. Will wait and see if it does anything. I jacked the drivers side up and removed the level plug expecting to be able to top up through that hole and was very surprised when oil started coming out. I had a drip tray in place and caught the oil - 800ml came out. You could see a slight yellow tinge to it but basically it was very dark brown. My car is at 103k miles. Not looking forward to replacing the oil because of the procedure with removing the blue plug and air filter below it with pliers of some sort. How do you know when the oil is at 60 degrees etc etc - drift in the replacement air filter!!!! and I take it that means taking the old one out in the first place will be a swine. Thing is should the oil pour out the level hole without the engine turning the box over? That is does having the oil being pumped round the gearbox reduce the level in the sump by a litre and that is why you check the oil level with the engine running?

Assich,
I would recommend to place the vehicle on level ground when checking oil levels. If you jack up only one side the oil will collect at the other side.
The documentation I have shows the level plug at the bottom of the transmission and is integrated with the drain plug. I am therefore puzzled as to which plug you removed

I took out the plug just above and behind where the driver's side drive shaft leaves the box.