2004 XC90 Temp gauge all the way in cold - engine up to temp

[bradmd_96]

Hi all,

I recently swapped out the engine of my 2004 XC90 T6. First swap was with a B6284T from a 99-02 S80 which we thought was a B6294T.
After fitting it we found it drove alright but wouldn't idle properly, most likely due to the different cvvt configurations (no cvvt on intake).

We have now fitted a B6294T from another 2004 XC90 T6 and since then the temperature gauge doesn't work. It stays all the way on the cold side.
I have checked the resistance of the fitted CTS and of another spare (known good/worked with previously fitted engine) placed in hot/cold water and there is change in resistance.

The CTS on the engine connected to the harness with a hot engine registered no temp on the gauge.
The spare CTS off the engine connected to the harness in hot water also registered no temp on the gauge.
The plug socket (harness side to ecu) for the CTS reads 5 volts on the pins with the ignition on.
I've tried a hard reset with battery disconnected and connectors tied together for 10mins+ and still no temp gauge movement when ignition is back on.

The car drives seemingly normal except:
The fan comes on even when the engine is started cold and stays on after shutting the engine off for maybe a couple minutes.
More noticeably, there is a significant drop in power.


Any ideas guys? The car ran much better with the B6284T engine in with a working temp gauge....

Thanks
Brad

[FLXC90]

Check the ground path for the harness/connector since you know there is power. Next logical step is to have DIM checked, repaired, or replaced.

If the sensor is good, check the harness, if the harness tests good check input vs output from CU, if they are all good, it's the gauge.