W211 ATF Temperature Value Question
 

Just got my iCarsoft MBii scanner....playing around, getting acquainted.

In the transmission menu I can read the value of ATF temperature. If I'm understanding it correctly, it wants to read the temp in either drive or reverse. However, it gives a reading in park but it's significantly different. In my case it was 69C in park and 49C in drive and reverse. Based on how long the car was sitting after I drove it, I'm sure the 49C number is correct.

If I use the temp to help set the ATF level, it has to be in park (unless I have an assistant....or I guess I can read the value in drive and then go check the level quickly). But somehow that doesn't seem to be the correct value.

Any thoughts as to why I get two different numbers?

If the transmission is not in D or R I believe the ECU substitutes the engine coolant temp as the default data value for current transmission fluid temp. Since the transmission fluid is cooled via the engine coolant heat exchanger this isn't a bad approximation if the car has been driven 20-30 miles.

Makes sense...thanks.

Tim, you're the first one I've seen on here with an E250 Bluetec. How do you like it? That's what the guy who sold me my CDI got.

It's pretty impressive, overall though I'd say its not an order-of-magnitude improvement over the W211. MPG and acceleration performance are a pretty much identical, I get low 40's on the highway from both cars. The W212 seems to have better steering feel and is a bit more refined than the W211 but I'd say its incremental improvement improvements in the newer car.

If I still was driving the 06 CDI I got from Tyler I wouldn't feel I was really missing anything by not having the E250 bluetec.

I am pretty impressed with the newer OM651 engine, I spent many, many miles driving OM615 powered 220D's and it still blows my mind that a 2.1 liter 4 cylinder diesel engine can pull like these things do. I haven't seen a torque curve diagram for the OM651 but my seat-of-the-pants impression is that it has more torque at lower RPM ranges than the OM648 but it seems to run of steam sooner at higher RPMs. The 722.9 transmission is perfectly tuned to take advantage of the torque curve and the car spends most of its time in the 1200-1600 rpm range.

Not crazy about the urea system but so far its caused no issues on the E250 or my wife's GLK250.

Overall it's met all my expectations.