The saga continues... 1.4i 16v Fabia AUB engine etc etc. Very poor cold starting, two-three cylinder running (barely) until it eventually picks up etc etc. After scanning these forums for hours, and having changed the coil pack and plugs, it looked like it may be the temp sender at fault. As the car needs to be used tomorrow, called the local (Cornwall) Skoda main dealer to see if they had one in stock, quoted the chassis number, only to be told after describing the poor starting, "Oh, your car has a two-pin sender unit, which only operates the temperature gauge. It's got nothing to do with the ECU. Only senders with four pins do that… You don't need one, sorry.". And that was that.

Surely the ECU MUST need a measurement of engine temp to work correctly? Does a two-pin sender preclude that? Is the engine temp read elsewhere by the ECU?

Is he talking BS, or dos he know something I don't?

Over to the real experts...

Well, a modern engine needs to know the incoming air temperature and the engine coolant temperature so that it can start, run and run cleanly. But I do know that there are some single element temperature probes - have you pulled the connector off to see how many pins it has?

There *will* be a coolant sensor for the ECU, but it may be seperate to the temp guage one.

You really need to get the car scanned or you could be changing parts for ever.

IIRC the coolant temp sensor on your car is at the bottom of the top hose outlet on the head, hanging more or less downwards - look to the right of the EGR valve. Its got 2 pins. You can check its resistance in-situ, about 250 Ohms at running temp and about 2000 Ohms at 20 deg.C. You can read its temp value in VCDS (Engine controller, 08 --> 01) it also shows up in my Gendan EngineCheck software. Sorry, don't know the part number though.

some cars do have seperate sensors for the dash and for the ECU

I have worked on one of these and IIRC there is a single coolant temp sensor (2 pin - wires are black/red and black/brown). This connects to the engine ECU, which is connected to the the CAN bus. The dash gauge then takes data off the CAN bus to display temperature. So there is basically one sender and its data is shared.