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Immo can be by-passed with 3 clicks using VAG Commander (which is why it's not a security feature, as any thief would know this!)
I have 2 ECUs......one for power (smokes) and one for passing tests.
Both have the Immo system bypassed.
 

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Thanks Paramedic!

Coolant temperature shows correct in measuring blocks. I have considered it.

Chould it still be a problem?
Im not sure I'd rule it out until its been resistance tested on a multimeter just to properly eliminate it.

I has a similar problem with a Porsche 944 a few years ago which while its a very different engine, the software and engine management isnt too dissimilar in terms the information it needs to run properly. If the sensor has gone lazy it will be as if its on choke all the time, and it will overfuel.

The Porsche did have a duff ecu, after it checked out as ok by an electronics company - lesson learned only use a Bosch specialist! a chance opportunity to try an identical ecu produced a perfect engine!
 

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This car has Siemens ECU.
Diesels have Bosch.

Or_GazM:
Does it work on Immo 3? And on Siemens ECU? More specificly Simos 3.5.
I only see Bosch on the description list - for VAG Commander 3.6.
 

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Thats interesting.......

Saying that the 5 pot 10v Volvos used a Siemens EMS. The overall principle is still the same though.
 

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I will remember to check out the resistance readings on the coolant temp sensor. When I start on that bloody van again =)
Wonder if anyone has the correct readings for it?

ElsaWin doesnt have that group 24 where the values would be.
 

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I will remember to check out the resistance readings on the coolant temp sensor. When I start on that bloody van again =)
Wonder if anyone has the correct readings for it?

ElsaWin doesnt have that group 24 where the values would be.
Google will help.
 

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Well Google is one thing - the VAG info, on the other hand, is something else - I was looking for VW specific info for this engine.
All I found through Google was people testing their own sensors. Or any random VAG coolant sensor. Are they all supposed to have same readings?? No matter what engine they are fitted on?
Although - if I am lucky - I think I have some, new, VAG coolant sensors on shelf..... somewhere. If I am lucky - one of them is the same that is fitted on this engine.....
 

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When I had the Porsche the information on the voltage range for the sensor was very easy to find. You might need the part number to find these specs. This sensor will be specific to the Siemens engine management system, not an 2.5 T4 engine. It will have been used in loads of other cars, VAG and otherwise.
 

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Paramedic - I didnt have correct blue two pin sensor - only a white, for coolant fan sensor.
BUT:
I resistance measured the coolant sensor on the car:
- infinitive resistance - open circuit!!
So ordering a new sensor today. I will have it next week.
Dont say it was that "easy" and it have been me, making it all that difficult....
I will deffinetly let you all know.
 

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The coolant "sensor" for the fans is simply a switch.....open normally, closed when at a certain temp.
 

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Im not talking about the fan coolant sensor/thermo switch (F18) on the radiator.
Im talking about the coolant temperature sender (G62) on the thermostat housing.
T4 also has third sensor - for the extra coolant pump below the radiator - thats located at the same place than G62 and is called F95.
On Golf IV - when the G62 goes bad - the car wont even start! I have changed one of those not long ago.... Thats why I have couple of different sensors at home.
 

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And this is the resistance ranges for correct G62 sender - Hella:

at 80 Celcius - 322 ohm
at 25 Celcius - 2080 ohm

So open circuite is not a good thing =)
Ill check it when I change it - but my guess is, when it reaches near 80 C - it starts working.

I checked the one new coolant fan switch I had - and even that one had 1,9-2,2 ohms (it switchedup and down to almost no resistance).
 

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Immo can be by-passed with 3 clicks using VAG Commander (which is why it's not a security feature, as any thief would know this!)
I have 2 ECUs......one for power (smokes) and one for passing tests.
Both have the Immo system bypassed.
How was it - did you know if VAG Commander works with Immo 3 and Siemens ECUs?
Or have you used it on Bosch, only? On what type of cars have you used it?
It looks quite unexpensive and perhaps a good idea to have at home, I recond.
We have couple of Passats (2000) ourselves. And we have quite many Golf IV and V in our "stable". And of course - a lot of T4 - both diesels and petrols.
And couple of these 2.5 AVTs have intermittent immo related problems.
 

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@Paramedic thanks for the advice to check the coolant temp sensor resistance. I very much wish I had heeded this advice before spending about a 1000 quids worth of parts... Although its been a good learning experience. So I replaced the blue two pin and the two green 4 pin sensors about a year ago. I decided to swap the blue two pin again yesterday and the old one was open circuit. The new one installed and cold engine is recording around 1000 ohms. As VCDS was clearly reporting the dial temperature reading, I thought it was all fine. Weirdly now though, with a cold engine the radiator is spinning slowly all the time, even with the van locked. It stops as soon as you unplug the blue sensor. I wonder If I have the wrong sensor in there now and it is telling the ECU the engine is still warm. Will try and find some specs
 

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Diagrams I found online suggest 1000 ohms is approx 50 degrees celsius. The engine hasn't been on for 24 hours and whilst it's been a warm day, the van is in Scandinavia. I am now suspecting this new replacement part is malfunctioning also
 

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I would have expected it to think that the engine was cold causing overfuelling - that was how the Bosch sensors used to fail. But its still off spec and needs sorting. It wont be helping!
 
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