M8000rider

I'm hopeing for some desperately needed help. I recently picked up a 2003 a6 with the 4.2l V8 the check engine light is on. It is the engine temp to low, says it's at -40 , changed the coolant sensor didn't help I'm assuming it has something to do with the thermostat and housing. The issue I'm haveing is finding a picture or diagram showing where they are located.

M8000rider

Well I have the entire engine bay gutted, and still cannot locate the thermostat. PLEASE HELP !!!!!!

Aviator6

Unless you are at the North Pole, there is no way that the coolant temp is -40. More likely a sensor issue. Wiring to the sensor or more than one sensor. Is the radiator getting warm as the engine warms up?

M8000rider

I've changed the main coolant sensor at the rear of the motor but that didn't fix the problem. the motor takes forever to warm up and cools down below 70 when on the highway so I'm assuming the thermostat is stuck wide open. I have the Housing, thermostat , and sensor sitting on my table but I am at a complete lose as to where it physically located on the engine to change it.

OT8

I recommend Alldata DIY, or if you are very cheap a chinese service manual pdf copy on ebay (much less convenient to use). Well worth it. As far as the -40 is concerned, that means you have an open circuit on the sensor circuit. Broken wire, bad connection, bad replacement sensor (it happens) or bad input on the ECM (rare).