Here’s an x-gauge for 545rfe trans. temp in Celsius, tested on my ‘06 WH hemi, and confirmed accuracy with a laser therm. on the case and oil temp probe down the dipstick tube.

It’s the same code listed on the scangauge site as tested on a dodge ram hemi, just with the MTH changed to get the value in Celsius;
TXD: 07E12118
RXF: 046105180000
RXD: 2810
MTH: 00050240FFEF

Here’s how I got to that MTH value, just in-case someone is googling like I was a few hours ago, and for me to refer to, when I’m trying to figure out another one and can’t remember wtf I did.

The DegF MTH is 000100400000.
Which means F=1/64*x-0 (where x is the ‘raw’ value returned from the car.).
That was confusing, because all the other temps I’ve seen are returned as either DegF or DegC and just need to convert from one to the other. I’m guessing on the 545rfe the temp is returned as DegF, but needs to be bit-shifted by dividing by 64.

So we’ve got F=1/64*x-0.
C=5/9*(F-32) (thanks to Fud for that one.).
Or;
C=5/9*((1/64*x-0)-32)
Which simplifies to;
C=5/576*x-160/9
The scangauge can only subtract whole numbers, so I round 160/9 down to 17 (which means the gauge will read about ~0.7deg high… better than low IMO.);
So the MTH needs to be;
C=5/576*x-17
Which in HEX (using 2’s compliment notation for -17) is 00050240FFEF.

This was originally just a post on the AJOR forums, I’ve replicated it here just incase another server crash looses some data.