XM temp sensor......

XMplory · Post by **XMplory** » 16 Feb 2005, 03:53

Could anyone please tell me how i test the coolant temp sensor for the ecu ?
I ran the car today with the temp sensor unplugged and i think it now assumes that the car is hot !
When i first started it today with it unplugged it was showing sympmtoms of no 'choke' (low tickover & needing to be revved to keep it going).
So hopefully it should not use as much fuel until i get the new sensor!

AndersDK · Post by **AndersDK** » 16 Feb 2005, 07:05

Unless the XM is opposite the systems on engines in other Citroens ...
- THEN a disrupted CTS would tell the ECU that the engine is arctic cold and therefore give "full choke".
If the cabling to the sensor is shorted out (or possibly earthed) the ECU takes this as hot engine and shuts down "choke".
The sensor itself is a NTC type resistor element, reading HI (towards 10K ohm) when cold, and reading LO (towards 300 ohm) when hot.
The exact ohmic value to temperature is not important.

XMplory · Post by **XMplory** » 16 Feb 2005, 08:04

I think you must be right Anders as i have just started the car (2:30 am) and got home and the car seemed to be on choke (high idle) plus i noticed that since its been disconnected the engine management light is now on all the time whereas before it would go off briefly and then come back on (hot or cold).
By the way its -4C here tonight when i started the car , but i bet its twice that in Denmark !

XMplory · Post by **XMplory** » 16 Feb 2005, 08:44

I still cant work out why when the temp sensor connector is plugged in the engine management light comes and goes ?
If the temp sensor is reading 'cold' all the time then the management light would be on all the time when the car was warm/hot ?

jeremy · Post by **jeremy** » 16 Feb 2005, 12:30

Won't the checking for the temperature simply be continuity - ie 'are you there?' - if the answer is open circuit or 'No!' the light comes on. The ECU can't check its operation.
jeremy

AndersDK · Post by **AndersDK** » 16 Feb 2005, 23:23

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by XMplory</i>

I still cant work out why when the temp sensor connector is plugged in the engine management light comes and goes ?
If the temp sensor is reading 'cold' all the time then the management light would be on all the time when the car was warm/hot ?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Check out the sensor with an ohm meter. If the sensor reads sensible within figures mentioned above - it is working. Then it is not the CTS which is pulling your hair and causing the fault lamp.