Coolant temp Gauge not reading

Wmkcchwhite · Post by **Wmkcchwhite** » 26 Mar 2013, 12:09

Hello,
I am sorry for all the posts with problems with this car. I have a 2000 S80 with the T6 engine.
The temp gauge is not reading. I have replaced the coolant temp sensor and have ensured that I hooked it up. I did a resistance reading after I let the car idle for about 5 min and was getting warm air. The Ohms reading was .646 I also did a voltage check on the engine side of the harness with the key on engine off and am getting 9.4 Volts.

Anyone have any advise on this issue?

Wmkcchwhite · Post by **Wmkcchwhite** » 26 Mar 2013, 15:28

Ok.
I was able to get some more info from a scan tool:
ABSLT TPS% 16.5
RPM 748
CALC LOAD 2.7
MAF 46.66
COOLANT -40
IAT -40
IGN ADV 1.5 to 6.3 (fluctuating)
ST FTRM 1% 0.00
LT FTRM 1% -0.8
ST FTRM 2% 0.00
LT FTRM 2 % -0.8
FUEL SYS 1 Open
FUEL SYS 2 Open2
O2S12 1.085
O2S22 1.085
MIL DIST (mi) 0
OBD2 STAT CA

I figure the coolant temp and IAT is where my problem lies but does this mean the Main Engine computer is bad or could something else cause this?

Thanks!

Post by **mikealder** » 27 Mar 2013, 13:30

The coolant temp sensor has gone open circuit OR the wiring between the ECU and the temp sender has failed (broken wire/ disconnected plug). This is why the OBD-II data is showing -40 as the temp you only get -40 when the resistance is infinity = open circuit.

Test the coolant temp sender using a DVM set to OHMS, apply the meter to the two wires on the coolant sensor connector on the side that is wired to the coolant sensor, the resistance you measure should correspond with the two graphs below:

I would expect a reading around 3000 Ohms with the engine cold, the temp scales on the graphs are in Deg C.

The second graph is taken from the same data but zoomed in to the area of more interest if looking in to why the radiator fan isn't working i.e the portion the car is often in when running including the points at which the radiator fan switches on at slow speed and high speed:

Hope this is of some help - Mike

muddblood · Post by **muddblood** » 10 Feb 2015, 12:50

Cannot load photo's

I too am having the same issue and would like to know the Ohm range of the sensor.