2012 corsa d cutting out & coolant temp sensor problems.

[givusaclue]

scanner :vauxcom

as above a14xer
2 coolant temp sensors, one in rad working fine, one in housing on end of head seemingly fine
temp reads fine on vauxcom in engine, read it through hvac & engine cooling data & from cold & it climbs in minus figures, once it hits -40 the engine cuts out, i can't work out where it's getting this figure from as there are only 2 sensors in the coolant according to vauxhall & they work correctly through other ecu's (genuine sensor & new multiplug fitted today)
no fault codes are generated, there is a hard code for cooling fan, it is very stiff to turn so it's goosed, but not the problem.

could this be a theoretical figure arrived at by an equation in the ecu?

i posted vauxcom as snapon does not show this data stream

any ideas?

[Deleted]

Check the radiator for a coolant sensor. Recent experiences with a vauxhall none start from cold I found the cooling system had three coolant sensors, one in the rear of the cylinder head, this will stop the engine starting, and I must admit that it is very specific that you can like I did fit a sensor on its own and the engine would not start, then I bought a new temperature sensor in the plastic housing complete. fitted that and the engine started every time. The thermostat housing also has a temp sensor in it. For me the one on the rear face of the cylinder head was the culprit. 

[givusaclue]

I can’t see one at the rear of the head, it does have a radiator one & the sensor in the coolant housing above the bell housing, the “sensor” in the stat housing is listed as a thermostat solenoid. The Vauxhall’s parts department assure me there is only the 2 sensors, but this -40 reading is coming from somewhere

[Deleted]

I had the exact same problem Steve. The coolant sensor at the rear of the cylinder head has more than one specification, and the reason I point this out is because I was given a brand new temp sensor to fit and when I did the engine would still not start. Having then spoken to Vauxhall they advised that they change all three sensors together when they get the none start problem. My example was a Astra. We purchased the complete housing with sensor in it supplied that fits at the rear of the cylinder head. When fitted the car started OK every time, and if I remember correctly the fault code must be cleared otherwise I think the engine will not start.  

[givusaclue]

the dealers told me there's only 2 & there is no falt code other than for a defective cooling fan which is defective
a14xer is the engine code of mine.
i'll have another look tomorrow but i didn't spot anything at the rear of the head

[sorted]

Unplug the sensors in turn while reading live data to see which is driving the dodgy reading? If neither at least you know it’s getting the it from elsewhere.

[givusaclue]

done that, that's why i wondered if the ecu creates this reading after vauxhall dealer telling us there was only 2

[liam99]

Has it got outside temp sensor, Try unpluging that

[givusaclue]

it has, that seems to read ok, but i will try it in the morning

[wheelnut]

I bought a cheap air-flow sensor from e-bay several years ago and fitted it to a Nissan. When I put the scan tool on it the temperature went to -40. I took it to be either a faulty sensor or some incompatability between the sensor and the ECU. I sent the sensor back and did not waste time trying to figure it out. I can't remember what the problem was with the car at the time.

[Deleted]

These are the ones I was referring to Steve.


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I've had these from the main dealer as this one and the engine would not start. 

How are you doing with it?

[givusaclue]

That goes in the housing at the end of the head above the transmission, we’ve replaced it & the plug that connects to it, no different

[trickydicky]

If coolant temp reads normally in ECM but incorrect in HVAC I would imagine there is a software glitch in the scantool, that data is almost certainly transmitted from ECM to all other modules, unless there is a separate temp sensor only used for HVAC (which I doubt)

The only other thing I can think of is that the ECM could look at rad temp and air temp and decide -40 coolant temp is wrong and substitute a value (yet still transmit the actual/bad value to other modules)

I would check coolant temp in other modules first, maybe instrument cluster if live data available

[jmac200t]

Dec 18, 2019 20:22:11 GMT 1 wheelnut said:

I bought a cheap air-flow sensor from e-bay several years ago and fitted it to a Nissan. When I put the scan tool on it the temperature went to -40. I took it to be either a faulty sensor or some incompatability between the sensor and the ECU. I sent the sensor back and did not waste time trying to figure it out. I can't remember what the problem was with the car at the time.

Had a mercedes that did the same thing due to cheap air-flow sensor

[Deleted]

Dec 22, 2019 0:54:07 GMT 1 givusaclue said:

That goes in the housing at the end of the head above the transmission, we’ve replaced it & the plug that connects to it, no different

For what they cost I'd buy the OEM one that comes fitted in the housing. I can't guarantee in your case a repair but my experience in the past showed that the cause of the fault was the new temp sensor in the bag shown as the cause. There must be more than one specification!