Vauxhall Zafira dashboard coolant light on

Not the connections,
I was suggesting a short circuit from the wire to power or ground.
is the light still on with no CTS connected?
If so then there is a short in the harness.
Old school test would be to short the CTS connector to ground and the lamp should light up.
Anyway testing at the multi plug between Terminals 9 and 38 is the complete circuit of wire/CTS which should be the same as just testing the CTS,
The wire isn't going to add any significant difference in resistance IF all is well.
The brown is spliced/shared with the MAP and MAF sensors.
Do the above tests.

Hi ..
thx for the quick feedback. I must clarify my previous statement.. the wires from cts were individually checked to ground and each gave the different resistance values as previously mentioned.
Your old school test is something I will need to do again.
If I understand your points correctly there should not be a short between both cts wires to themselves or each to chassis ?.
But the strange thing is when both cts wires are shorted together the fan comes on..
So this proves theres no short between the two cts wires...
or am I getting misled ?.
Thx.

Hi .
I have just redone some tests.
CTS disconnected there is about 1.2k Ohms from blue wire to ground and 0.5 Ohms from brown to ground.
with cts disconnected the fan runs full.
With Ignition on there is 5
volts on the brown wire.
I will check the brown again in the MAF.
After this I have to get ready for work...
so till next weekend.
Thanks guys .
Regards

Whoops!
Most humbly I'm a careless ass.
I referenced what I thought was the wiring diagram for your car but I was on the petrol Zafira.
Terminals at the ECU for the CTS are 93 and89 plug B.
Brown wire shares with oil temperature sensor and MAP sensor,
unplug those then check at ECU connector 93 89 for the CTS.
Now I'm not really a fan of multimeters,
What I use in a situation like this is my own variable resistance "Pot".
I replace the CTS with this then dial up/down the resistance while checking the live CTS data on my scanner.
But in writing this apology it occurs to me as it's on the same circuit as the CTS it would be an idea to unplug the oil temp sensor and see what happens.

As I am now physically tired after a days worth of standing bent over an engine
I have packed up in preparation for work.
If no problems arise during the week then I hope to check your new suggestions next weekend.
In summary.. I connected and disconnected the MAP and MAF and checked for continuity between the shared brown wires all ok.All was done with and without engine running. But no change to status of dash light .. still on.
However a note to add..the light has reduced in illumination and is about half bright.
Hope to follow up next week.
Sincerely appreciate your assistance thus far..
Regards.
Abu.

A change in state is excellent!
And leads me back to a short circuit.
Dim bulb clearly means less than full V.

Hi 1/4 Drive...
Its my trusty Zafira light..
it went intermittently dim but now its upto full brightness.
Anyway With reference to last week.. you suggested to check the oil temperature and CTS wires ...I will check those
however Im reasonably confident using a multimeter and reading a wiring diagram..
I was wondering if possible to save time and frusyration for all if I could possibly sample a wiring diagram for the Y20TDH dashboard and engine areas..?
What say you ?.
thx..
Abu.

Unclear,
Do you mean buy a manual?
absolutely.

Hi sorry for being unclear...
I meant if there was one I could sample as in borrow temporarily for diagnosing the problem.. or if ****ible a few pages of pdf which I could download ...
Thx..
Abu

Sorry no idea how to get my wiring diagram of one program and onto website,
Mechanic not computer geek!
All I can do is suggest testing at the ECU/plug,
plug "A" CTS terminal are ECU 8 (blue) and terminal 45 (brown/red).
One of those is going to be +V and the other is signal return.
Ignore my other advice I had the wrong diagram up.
Also that car has an instrument panel ECU chip,
Fed by fuse 13 and grounding through the ECU terminals # 2/13/14/27 and 37.
So it might be possible to check the dash by grounding T#2 13 or 14 to see which triggers the temp lamp,
"might!
And it might be easier to bite the bullet and buy a manual.

Hi 1/4 Drive ..
thx for the latest tips...
I will investigate and see what transpires...shame you cant upload a couple pages ..
just out of curiosity how much is a manual ?
thx...
Regards
Abu.