MG ZT Cdti 2003 safe mode temp gauge maxed

[Mike Lis]

Hi guys,
I have MG ZT Cdti 2003
Cars in some kind of safe mode now as i cant go any faster than 15mph or so.
Temp gauge goes to the max as soon as i turn ignition on. (Checked with obd reader and it shows teperature over 100° with cold engine, no error codes)
No warning lights on dash.
Also it takes like 10-15secs to start the car.
Changed engine coolant sensor (the one in the centre of engine below inlet manifold, not sure if theres more than one)
Checked old one with tester at 20k and it seems to be working fine, also connected it straight from the ecu(to be sure theres nothing wrong with wires between ecu and sensor)
No succes so far
Thinking of buying second hand ecu but would it work straight away or itll need some coding?
Any ideas?
Any help would be much appreciated.
Thank you in advance.

[Rob Bell]

Hi Mike,

Luckily a few of us have ZTs too, but the best place would be on one of the ZT/Rover 75 forums (the Rover 75 and ZT club forum is very good - and then there is also the Zed register).

This one sounds a strange one. Never had this on my ZTT CDTi. I've not heard of a 15mph safe mode? I wonder whether there is an ECU fault - they can flood as leaves and other debris can block the rain drainage channels.

A second hand ECU isn't necessarily going to help thanks to BMW ancestory of the CAN BUS electrical system - it'll throw up faults relating the the instrument pack (IPK) and light switch unit (from memory). I can be coded in using T4. There are a few guys on the Rover 75/ZT forum with these tools who can hopefully help you. PhilT4 is based in Milton Keynes, but you may find someone else a little closer

Good luck and let us know how you get on!

[cath's mg]

Hi Mike,

PhilT4 is based in Milton Keynes, but you may find someone else a little closer

Good luck and let us know how you get on!

Phil has done some work on my ZT Cdti and he knows his stuff. It cant hurt to give him a phone call.
Send me a PM if you want his number.

Gary