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So I've been trying to figure out how to get the transmission temp to display on the SGII for my 2008 Mazda3 (2.3L, 4 cylinder, auto). I came across this thread (http://www.cleanmpg.com/forums/showthread.php?t=6068) while searching, and going along with what that thread says, I have no problem looking for the trans temp since I installed an Auto Meter trans temp gauge after tapping the output line for the transmission.

My problem is I'm not sure where to start. From what the SG tells me, the car is CANSF, so just for the heck of it, I entered all the provided CANSF trans fluid temp codes on that document on the SG website, and none of them worked (kind of a given).

Going back to the thread I mentioned, I entered "0100" in the CMNDS function on the SG, and got a value that began with 4100 and ended with four zeros, which is an even number, but I'm pretty sure that's not the trans temp.

I know for a fact that the car does report the trans fluid temp over OBD-II since the dealer and a friend of mine both have laptop-based scanners that can read anything that the ECU reports over OBD-II, and trans fluid temp is one of them. It's just a matter of figuring out how to get the data from the SG, since I don't exactly have $25,000 to spend on a laptop-based scanner.

Specifically, I'd like to know how to use the CMNDS function to find the transmission temp, and how to code the received data into a format that the SG can use (TXD, RXF, RXD, etc).

I downloaded the XGauge Coding Information from the SG website, and as far as I understand, TXD is what the SG transmits to the car, RXF is the receive filter, RXD is the raw data (the reply as a result of the TXD request), and MTH is used to properly scale and adjust the data.

So then, what's the relationship between what I send in the CMND function, what the thing received is, and how to translate it into something the SG can use? Can I translate what I send in the CMND function into hexadecimal format and enter that under TXD? Likewise, can I translate what is received in the CMND function and enter that under RXD?

I'd much appreciate it if someone could explain this to me so I can better understand it and hopefully be able to find the data I want. I looked on the Wikipedia page for OBD-II PIDs, and since transmission temperature isn't a standard PID, I am guessing it's a vehicle-specific one?

Tranny temp seems to be an elusive sucker! A lot of FLM vehicles use the mode $22 PID of $1674 from the TCM, but obviously not all of them do. As far as the CMNDS, for CAN protocols it takes what you enter and prefixes it with $7DFxx where xx is the number of bytes that have been entered. It then tacks on a CRC byte at the end. So your $0100 gets sent out over the bus as $07DF020100zz. The response chops off the same stuff that is added so instead of seeing $07E80741xxxxxxxxxxzz you just see the stuff starting at $41.

The $07DF addy is a functional request that any module listening can respond to. In CMNDS you don't know who responded since that is filtered out for CAN, but you can figure that out with an xgauge. To talk to a specific module, the addy changes to $07E0 for the PCM, $07E1 for the TCM, $0760 for the ABS, etc.

The problems with the tranny temp on certain vehicles may be due to them being used on a different network than the main HSCAN network. As configured now, the SG can't connect to any of the other networks.

If your friend with the scanner can hook up to your car and read the tranny temp, you might be able to figure out what the scanner is sending to the vehicle if you hook your scangauge up and set it to listen to what is being sent. You would need an inexpensive y-cable like this: http://www.obd2cables.com/products/obd-cables/obd-ii-cables/cable-j1962m-to-2-j1962f-y-cable-1ft.html