Engine coolant temp -49°C in group 001 - but why?

[Jonas_R]

So I'm having some issues with my coolant temperature.

I just had the engine rebuild and changed MFTS and engine coolant temp sensor.

So the first problem is that when I try to read out the engine coolant temp it says -49°C in group 001 with latest vcds.

I have tried to put in my old G62 sensor and no change. Also measured my old sensor at room temp and it is 1800ohm so should be ok.

There is 5V at the plug as well.

The ECU only shows a internal control module error, but I think this is checksum related and I have asked Marc from EFI for a new set of bins so I can burn some new chips. But not sure that this could be the culprit? I have set of old eeproms, and I could try and fit them instead, just to see if the checksum error goes away.

Any suggestion what to meassure?

[twoqu]

It will show that figure when the engine is not running.
There is a technical expanation which is something to do with ADC!

http://www.s2forum.com/forum/showpost.php?p=936880&postcount=7

[UrS4boy]

G62 Engine Coolant Temperature Sensor info

Here is a link to the 20VT engine coolant temp sensors (G62 for the engine and the MFTS for the instrument cluster):

http://forums.quattroworld.com/s4s6/msgs/20985.phtml

I suspect with a -49C reading, the ECU is signalling that it is not seeing the G62, i.e. you have a broken connection. This most often occurs inside the connector boot at the engine when people remove the G62 without disconnecting it from the harness first.

[Jonas_R]

So I have a connection between pin 30 in the ECU plug and the plug for the g62 sensor.

And it shows -49 even though engine is running.

[UrS4boy]

So I have a connection between pin 30 in the ECU plug and the plug for the g62 sensor. And it shows -49 even though engine is running.

Pin 30 is just a ground. What about Pin T55/45

[Jonas_R]

I measured 5v at the plug for the g62 that tells me there is a connection?

[UrS4boy]

I measured 5v at the plug for the g62 that tells me there is a connection?

So you have 5V in the female Pin 1 of the connector and you have continuity to ground in Pin 2 of the connector?

And you measured the resistance across the two male pins of the G62?

[Jonas_R]

Yes, yes and yes

I tried stock chipset and the I don't have the internal control memory error. But I can't start the car with that.

I don't know if the internal memory error can mess with temp reading somehow.

When I get the chipset and the fix from Marc I will start the car again and see if that helped but I doubt it.

Any other suggestions?

[Jonas_R]

So got a fixed chipset from Marc and I can read the g62 temp now.

But it is running to hot, that's a nother problem all together