Limp home mode

[bc2000]

Hi, I was wondering if anyone has a solution to this. My pug 807 Executive, 2l petrol automatic keeps going into limp home mode. There is usually a clunk and the display will say "Automatic gearbox faulty" and it will go into limp home mode. All I have to do is switch off the engine and switch on again and it will be fine till the next time, which could be 2min or 2 days. There doesn't seem to be any pattern, it can happen after 5mins or 30mins, at low/high speed. It does always seem to happen on motorway slip roads just as you join the motorway. I used to stop on hard shoulder but sometimes it would do it again. If I drive for a while in limp home mode then restart it tends to be fine after that. My local mechanic can't find any fault and I had the gearbox oil changed and it made no difference. Help!

[spider]

Lexia (Planet) diag will show the real fault here. Other / general diagnostics may not as it could be a manufacturer specific code.

Note: The replacement oil was the correct one was it ??? They will suffer (very!) badly with the wrong oil in them aka: General ATF.

One fault I saw recently on a 207 (same transmission) the cause was actually the selector switch on the gearbox, the plus was a bit corroded. Once this was cleaned up (bit of a pain to do actually but cheaper than a switch!) it was fine.

[bc2000]

Thank's spider.
The oil replacement was done by Mackie's in Glasgow, they are specialists in automatic gearbox's so I would imagine they used the correct oil.
Is the selector switch hard to check?
I was hoping it was a problem with a sensor. It's been doing this for 2 years so if there was a real problem I imagine it wouldn't have lasted this long.
Again thank you for your time.

[Stickyfinger]

Thank's spider.
The oil replacement was done by Mackie's in Glasgow, they are specialists in automatic gearbox's so I would imagine they used the correct oil.
.

Never BET on that

[spider]

Its kind of detailed in the Haynes but diag will be more accurate as that should indicate the positions correctly.

To get at it, its not bad but its a bit fiddly. Basically:

Battery out
Battery tray out ( a few bolts )
Selector cable off (you'll see this once the battery tray is out)
The switch is sat on the selector 'arm' , a vertical shaft.
If you are going to remove it, please please make a small mark on it and the shaft so it goes back in the same place as the bolt holes are slotted a bit to allow for a bit of adjustment. If its in the wrong place it will cause issues.

[xantia_v6]

Mackie's should know what they are doing, they are the people who recondition 4hp20 torque converters.

The only way to check the switch is to have the car connected to a Lexia, which would give you the fault codes anyway.