TD5 Gearbox fault.

Hi guys, first post so go steady with me! lol

So I buy quite a few TD5's and they often have the xyz switch problem, M&S lights flashing and limp mode 3rd gear.
I normally remove (clean up)the switch and refit, problem solved.....not this time!
The battery is strong! 13.8v

I've cleaned the switch and the same problem, I've replaced the switch with a known faultless one off one of my other cars and still the same...so this rules out the switch right?

There's no oil in the ecu, or plugs.
the odd thing is the gear selector lights are not illuminating(ive replaced this too) also the PNRD on the dash clocks doesn't show anything at all in any gear.

The reverse sensors bleep in reverse and activate the rear wiper.

So my question is where do I go to next.
thanks

jonnymoore said:

Hi guys, first post so go steady with me! lol

Click to expand...

2nd post!

Does the BCU think its a manual, rather than an auto? Common problem, but worth checking. You will need a Nanocom or a Hawkeye from a friendly local to plug it in and see. Also check the wiring that runs around and over the top of the T box, that comes from the XYZ switch. It has a habit of chafing through on the metal P clip that holds it to the top of the box. You will have to remove the centre console to be able to see it properly. This sounds more likely, but always a benefit if you can get it plugged in. The reverse switch will work anyway.

Tony

I would first check that the xyz switch is actually receiving a positive feed from the bcu which is the source of power to the wxyz circuits which provide the gear position signals to the bcu ecu and eat ecu which in turn control the lights by the gear selector and display in the instrument panel.
The circuit is
Bcu ( front passenger footwell )connector 0663 (dark grey) pin 10 NP (brown/purple) 0.5d wire.
Connectors 0668/0681 (white male/female) pin3/3 NP ( brown purple) 0.5d wire, under central console by hand brake.
Connector 0675, (grey plug to xyz switch) pin 8, NP (brown purple) 0.5 d wire.
If this is the case it could be that the bcu has changed its settings from automatic to manual transmission as has been reported, the bcu is at fault or there is s a fault in the power supply to the bcu used by the xyz system as this is a stand alone supply, failure of which would not affect other systems controlled by the bcu.
If it is not the bcu changing the settings from automatic to manual transmission, there is a fix which worked for me with the same problem.

Thanks gents.
Is the bcu the gearbox Ecu under the passenger seat?

Also is this part plug and play, or would it need to be recoded?

Bcu is the body control ecu located behind the front passenger glove box and controls among other systems, indicators, hazard lights Windows, doors and the vehicle security .
Eat, electronic automatic transmission ecu is located under front passenger seat.
Bcu is not plug and play, needs to be programmed to your vehicle spec and synced to security system.
Care needs to be taken if buying a used one that it is in an unlocked state as a locked one is useless.
I had these symptoms as an intermittent fault and it took 12 months, Many trips to auto electricians at a cost of £1500 and much reading up before I pinned down the cause of the fault and I could instruct auto electrician how to fix the fault with a simple wiring fix that cost £40.
If some one had checked that the xyz switch was actually receiving power from the bcu initially, all the time and money could have been saved.
I am not categorically saying this is the cause of your problem but it is an easy check to carry out a as you have already removed xyz switch twice.
The socket configuration in the plug to xyz switch is 3, 4, 3 and pin 3 has no wires going to it being unused.
The reason for checking that the bcu has not changed its settings from automatic to manual transmission is that in manual it can turn off the power supply to the xyz switch and it is a known fault that can happen for no apparent reason and can be rest with test book, nanocom or hawkeye diagnostic tools.
If you do check with above diagnostic tools also check the wxyz live feeds in the bcu and eat ecus and with the ignition turned on manually select d, 321 and see if any signals are received, you should register signals in prn as they receive power from other sources.

If a diagnostic tool is already there IMO the simplest way is to read the fault code stored in the EAT ECU first cos that might show the problem from the beginning as beside the feed from BCU issue there can be other 18 reasons for flashing M+S and limp mode many of them not XYZ switch related

After many hours inside and underneath , I finally found the problem.....underneath the center consul there's a load of electrical wires, some going to the xyz switch. Well one of those wires had obviously been rubbing and had actually snapped. Very simple fix, and no money spent.
BTW, I went to Nick Kerner 4 wheel drive today, to have the problem diagnosed. Thankfully they were too busy, but the advise was to have the gearbox rebuilt at a gearbox specialist....lol

Thanks for all your replies.