My car has been throwing a code since my coolant system was worked on over the course of many months. Basically, many components were replaced due to a continual leak (water pump, coolant flange, thermostat, hard pipe, j plug, sensors, etc.). Since that time, with the code I get the fans on cold startup. This wasn't happening until half way through the trips to my mechanic for various coolant work to track down the many problems. On cold start, the fans come on a medium speed (clearly audible from inside the car - I've heard jet engine speed and it's not that) and then shut off just after the temp gauge starts moving up. This has been consistently happening ever since regardless of the outside temperature (single digits to 60 in Massachusetts). I had also been complaining to my mechanic about a low idle of around 800 RPM or slightly above on cold start and even after the car warmed up, then my car crapped out and had to have the engine speed sensor replaced. Even after that, still hovering around 800 RPM or slightly above since. HOWEVER, a few weeks ago, I noticed that one magical morning, I started it up cold and the idle speed returned to about 1200 RPM like it used to do back in the day for a minute or two, and then dropped down to about 900 AND NO FANS. I drove 30 minutes to work, came back later on that day, started it up and got the same results - engine speed about 1200 for a minute or two and then dropped to 900 and no fans. Of course, it hasn't done that since and has reverted back to its old ways with the lower idle and fans at cold start. I'm due to go back in for a few wear and tear items and this has stumped my mechanic. Any ideas?? Much appreciated!

 

What was your solution?
Having the same issue.

 

Post your code(s)

Was the G2/G62 Coolant Temp Sensor replaced?

 

P3081.
So yes, pointing to the sensor again.
Both sensors were replaced.
Thermostat 18 months ago.

 

G2/G62 is one physical sensor, with 2 sensors inside the one housing. You want the (long ago) updated green top version. One reports to the ECU and one reports to the dash gage. Use vag-com to see ecu coolant temp after cold engine start. Just because the dash gage reads accurately does not mean the ecu is.

 

Replaced the G2/G62 sensor at the firewall and the temp sensor in the lower rad hose near the rad.
Like I said thermostat was done 18 months ago.
If I clear the P3081 the fans seem to work properly....at least not turning on full speed at start up.
Seems like it might be the thermostat again as it never seems to go up to 90C on the guage and stay there like my Passat did.
What is the sensor on the thermostat housing for?

I'll post my codes tomorrow.