Coolant temperature sensor, emissions problem

[Boogins]

Please help!! I've just changed the coolant temperature sensor (bitch of a job to get to) and after running a while I now have an emissions fault light.
After double checking everything once the light had come on I found that there are two small pipes running at the back of the engine bay and in my struggle to fit the temperature sensor one had come disconnected. Could this cause the emissions problem.
I've now connected the pipe back up but the fault remains (not sure how these things work as I'm an electrician not mechanic!!). It now seems as though the car has gone in to a safe mode and there is severe lack of power. Temperature gauge seemed to be working fine so presume new CTS to be working.
Any advice greatly appreciated. I'm gonna be in my other halfs bad books having naffed up her car!!
Sorry for the essay but I know you guys out there may know what I'm dealing with having already helped me get a new wing under warranty!!

[rowdy-999]

Engine?
Are you talking about the ECU temp sensor, or the one for the temp gauge ?

Ive changed a 1.9tdi CTS and it was an easy 5 min job.

[Boogins]

It's the sensor at the back (green one) under the boost pipe. I'd been having problems with temp gauge not reaching 90 and had noticed a decrease in mpg so decided to change sensor in my wisdom as this would seem to be the cause (with out running any sort of diagnostics) It was a 5 minute job (half hour) just a pig to get at and once out remove old sensor from plug!!
Car ran for 10 minutes before light came on. Fairly sure it was due to the small pipe at the back of the boost pipe not being connected, only thing is now it's reconnected obviously the fault light is still on! Any way to reset fault light and see if occurs again once reset?

[rowdy-999]

A basic code reader will give you an idea why the light is on, and maybe reset it if the problem has resolved.

[Boogins]

Well having driven a couple of short journeys the car seems to have lost no power as first thought and now the engine management light has decided to go out!!
Now just need to go far enough for the car to warm up properly and see if the temperature gauge is behaving properly!!

[niall campbell]

it takes a bit longer in this frosty weather to get up to temp

[Boogins]

Before changing the sensor I'd done a 50 mile journey and temp gauge never reached 90 and randomly dropped 10 or so degrees now and again!!

[niall campbell]

Change the thermostat

You could actually buy a new thermostat, take the old one out of the car and compare them cold. Does the old one look as if its closed properly ?

Then boil them both in a pan of water, they should open at the same time

I would do this test just to make sure it is the thermostat, as new can be faulty .................................. plus peace of mind ................... and a good practice

[Boogins]

Yep, think it is the thermostat now! Behaving exactly the same as before, at least I've ruled out the CTS now to change the thermostat!!