toast_S4

like the title says, i am getting about 12 mpg - coolant gauge works sporadically. When it does work it is right where is it supposed to be. i just put a coolant temp sensor in tonight (035919369M) and its no different! Ive searched on this sensor and the MFTS. Do we even have a MFTS?? If the AAN does, the archives say the ecu doesn't use this for fuel/boost so whats the deal? I haven't tried the CC yet, do i really need to?

tpierce

AFAIK, the temp gauge uses the MFTS, the ecu uses a sensor in the back of the head.

MA_2.7t

If it wobbles around you have a bad thermostat.

UrS4boy

Correct x 2. Gauge = MFTS, ECU = G62 temp sensor.

UrS4boy

And yes, you should check the temp gauge against the climate control Ch. 51 reading (with the heater on). If the CC reading is good but the temp gauge is low or moves around, its a dead MFTS (which has nothing to do with the ECU on an AAN). However, the CC value is low and the gauge is low, then you probably have a broken thermostat and its stuck open (eventually temps get up there but only around town).

See the link below<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/150040.phtml">G62 and MFTS info</a></li></ul>

UrS4boy

<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/198575.phtml">Link to Climate control head diagnostics</a></li></ul>

MA_2.7t

It reports idle correctly but is off anywhere from 4-800rpm otherwise. I think.

toast_S4

replaced it not 3 months ago.
I saw the links to the FAQ, they didnt say what the MFTS did in the AAN...now i know! its crappy ecu and temp gauge dont run off of one sensor

so i should be getting better fuel economy, its just the gauge will work sporadically? also, what MPG are you guys getting 18, 20?

MA_2.7t

Things can die prematurely.

Sloooo4esT

then your MFTS is bad or you can try cleaning it, 12 mpg is awful low, mfts can also cause gauge to work proper sporadically