Possible wiring fault and ecu removal

[Dave_M]

Evening all

Got an issue with my Ed30.  VAGCOM had shown an intermittent fault with the radiator outlet coolant temp sensor, so I swapped it for a new OEM sensor last weekend.  However that doesn’t seem to have fixed the problem so I logged the sensor voltage on my commute yesterday, and it shows the temperature reading intermittently dropping to -45 degrees (which indicates the sensor going open circuit).  Now I might be unlucky and have got a dud new sensor, but I’m guessing it’s more likely a break in the wiring loom.

I’m going to try to check this tomorrow by wiggling the wiring loom whilst watching the temp reading on VAGCOM. But if it is a break I’ll need to replace the wires and am thinking I’ll buy a new connector with terminal pins and then run a new pair of wires - but have a couple of questions:

 - does anyone have a wiring diagram or can tell me which pins on the ecu this sensor connects to?
 - the Haynes “book of lies” says that if the ecu is disconnected then all settings are lost and VW have to reinstate the basic settings.  Is this really true?  I’ve disconnected several ecu’s in other cars before without issue, and surely there’s no difference between disconnecting the wiring from the ecu and disconnecting the battery?

 - finally, is it possible to buy replacement terminals for the ecu connector?  I’ve found replacement 2 pin plugs to fit the sensor on eBay.

Thanks
Dave

[pudding]

Check under the vacuum pump and see if the wiring harness has rubbed through there.  Pretty common.

The region specific official wiring diagrams are hard to get hold of.  You'll need to do an end to end continuity check with a beeping multi-meter to find the wire colour.  It will either be a corroded/broken terminal at the sensor end, or a break in the wire.

[Dave_M]

Thanks.   Not sure where the vacuum pump is, but found the break last night at the 4 pin connecter clipped to the front of the gearbox.  It was literally hanging on by a thread and as soon as I moved the connector one of the wires just snapped off.  Just need to fix it now -job for next Saturday!

Dave

[pudding]

Ah nice and easy to find then, but not to get at!

[hannarase]

Hi. In my life, I also had a lot of severe problems with my car. Too I had defections with the radiator outlet coolant temp senor. Like you, I was trying to find solutions to this issue. Also, I bought another sensor and others, but nothing helped. I understood that I am very poorly trained when it comes to cables in the car. I had a lot of photos with instructions, but this wasn't enough. I wanted a qualified electrician to solve my problem, but it isn't easy to find a good one in this field. But all is possible, an acquaintance of mine once said about an electrician company from our country. I found them on the internet, I read about them, and I understood that they are those I need because they are more than regular electricians; they are Level 2 Electrician Castle Cove. They fixed my problem with my radiator. Now the temperature is all right, and I don't have any issues.