Polo Vivo Coolant Temperature Sensor Issue

[sa80]

Hi All,

My 2010 Polo Vivo has been struggling to start the past 2 months. Most of the time it cranks and barely manages to start but if it's really hot or cold then it won't catch at all. Once it does start, there are no issues with idling or power delivery while driving.

After browsing the forums extensively I first had the battery and starter checked which seemed to be fine, I then replaced the fuel pump relay and finally replaced the Coolant Temperature Sensor the other day.

Unfortunately this was all to no avail. The car still does not start "strong" and if it is hot, as it has been recently, it will just keep cranking until I pump and floor the accelerator at which point it barely manages to catch and I have to over-rev it for it to stabilise.

I am wondering if it could be the actual wiring from the sensor to the ECU which could be a problem?

Any help would be much appreciated as I am at my wits end with this car!

[mellos]

Hi All,

My 2010 Polo Vivo has been struggling to start the past 2 months. Most of the time it cranks and barely manages to start but if it's really hot or cold then it won't catch at all. Once it does start, there are no issues with idling or power delivery while driving.

After browsing the forums extensively I first had the battery and starter checked which seemed to be fine, I then replaced the fuel pump relay and finally replaced the Coolant Temperature Sensor the other day.

Unfortunately this was all to no avail. The car still does not start "strong" and if it is hot, as it has been recently, it will just keep cranking until I pump and floor the accelerator at which point it barely manages to catch and I have to over-rev it for it to stabilise.

I am wondering if it could be the actual wiring from the sensor to the ECU which could be a problem?

Any help would be much appreciated as I am at my wits end with this car!

Hi there I've been monitoring for responses here, I'm in the same boat with my polo and I reckon we should look into the wiring, what I did find is that turning the ignition on and off a few times makes it start sooner, did you come right by the way??

Sent from my ANE-LX1 using Tapatalk

[mellos]

Hi All,

My 2010 Polo Vivo has been struggling to start the past 2 months. Most of the time it cranks and barely manages to start but if it's really hot or cold then it won't catch at all. Once it does start, there are no issues with idling or power delivery while driving.

After browsing the forums extensively I first had the battery and starter checked which seemed to be fine, I then replaced the fuel pump relay and finally replaced the Coolant Temperature Sensor the other day.

Unfortunately this was all to no avail. The car still does not start "strong" and if it is hot, as it has been recently, it will just keep cranking until I pump and floor the accelerator at which point it barely manages to catch and I have to over-rev it for it to stabilise.

I am wondering if it could be the actual wiring from the sensor to the ECU which could be a problem?

Any help would be much appreciated as I am at my wits end with this car!

Hi there I've been monitoring for responses here, I'm in the same boat with my polo and I reckon we should look into the wiring, what I did find is that turning the ignition on and off a few times makes it start sooner, did you come right by the way??

Sent from my ANE-LX1 using Tapatalk

By the way when I scan it on VCDS it says intermittent fault coolant temp sender but had it replaced twice already to no avail.

Sent from my ANE-LX1 using Tapatalk

[panic-mechanic]

change the plug. when you start getting issues like intermittend then it can often mean the pins in the plug is making bad contact

[mellos]

change the plug. when you start getting issues like intermittend then it can often mean the pins in the plug is making bad contact

Ok thanks I will try and change the plug.

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[panic-mechanic]

buy a repair plug from VW. comes as a plastic housing and the wire and pin seperately

[mellos]

buy a repair plug from VW. comes as a plastic housing and the wire and pin seperately

Ok thanks, is that what I must ask for?

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[panic-mechanic]

yes

[sa80]

Thanks for the response guys,

After a while of mulling it over in my mind, I've also come to the conclusion it must be wiring related. Will try to get a new plug and report back if it worked.

UPDATE: Before installing the new connector, I decided to check the continuity of the harness. Connected the positive to the pin and grounded to the engine block and measured 5V, also checked continuity of the earth pin - The only conclusion after checking that the sensor is reading a resistance drop when warming up and that the harness is fine, is that the ECT is not the cause of the starting struggles.

UPDATE 2: One thing I have noticed as well is that while the temperature gauge usually indicates 90 deg as normal, now and then it will actually go past the 130 deg maximum and almost sit "horizontally" as if it has reset itself past the maximum. I am not sure if this could be a related issue or not.

[mellos]

Thanks for the response guys,

After a while of mulling it over in my mind, I've also come to the conclusion it must be wiring related. Will try to get a new plug and report back if it worked.

UPDATE: Before installing the new connector, I decided to check the continuity of the harness. Connected the positive to the pin and grounded to the engine block and measured 5V, also checked continuity of the earth pin - The only conclusion after checking that the sensor is reading a resistance drop when warming up and that the harness is fine, is that the ECT is not the cause of the starting struggles.

UPDATE 2: One thing I have noticed as well is that while the temperature gauge usually indicates 90 deg as normal, now and then it will actually go past the 130 deg maximum and almost sit "horizontally" as if it has reset itself past the maximum. I am not sure if this could be a related issue or not.

Have you changed the plug and wiring yet I'm kind of eager to see if that was the cause, I don't have any fluctuating heat guage problem though just the intermittent starting problem

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[sa80]

Finally have a further update to this.

Sent the car into get it's annual service and asked the mechanic to run a diagnostic to see if he could pick anything up.

As always nothing was recorded, no problems with ECT or anything else however he did mention a bulletin came out for the Polo with regards to the throttle being an issue. After some fiddling he thinks that it may be sorted.

Problem is when driving it the day after service, the EPC light came up when pulling away from a robot and car went into limp mode. Had to stop and restart the car to get it to clear, the issue did not appear again the rest of the drive. (Never had this issue with the car before)

Mechanic said it may need to have the entire throttle body replaced.. not looking forward to that as I would hate to spend the money just for it to not work, but only time will tell.

[Newbie6R]

Finally have a further update to this.

Sent the car into get it's annual service and asked the mechanic to run a diagnostic to see if he could pick anything up.

As always nothing was recorded, no problems with ECT or anything else however he did mention a bulletin came out for the Polo with regards to the throttle being an issue. After some fiddling he thinks that it may be sorted.

Problem is when driving it the day after service, the EPC light came up when pulling away from a robot and car went into limp mode. Had to stop and restart the car to get it to clear, the issue did not appear again the rest of the drive. (Never had this issue with the car before)

Mechanic said it may need to have the entire throttle body replaced.. not looking forward to that as I would hate to spend the money just for it to not work, but only time will tell.

Did you manage to figure the problem out?