fixdrive

Hi all,
I need help with reading transmission fluid temperature from OBD2 code reader and TorquePro application.
The vehicle Lexus RX350 2010 made in Japan, sold in Canada.
I assume that PIDs are the same as for Toyota Highlander. The settings are below:
Name:Transmission Fluid Pan Temperature
Shortname: ATF pan temp in
Mode and PID: 2182
Min Value: 0
Max Value: 300
Scale: x1
Unit type: F
Equation: ((((A*256)+B)*(7/100)-400)/10)
Header: <blank>

Name:Transmission Fluid Temperature Converter out
Shortname: ATF temp conv out
Mode and PID: 2182
Min Value: 0
Max Value: 300
Scale: x1
Unit type: F
Equation: ((((C * 256) + D ) * (7/100)-400)/10)
Header: <blank>

The issue:
With ignition on I get -40F for pan and converter temperatures. Probably OK as may be sensors are not activated.
Running idle I get 110.5F for pan temperature but only 24.5F for converter. It is currently 77F outside.
What am I doing wrong while getting converter temperature? Could PID or formula be different?

salimshah

When you idle to warm up , your engine gets warm, but the transmission fluid [assuming you are staying in Park] does not heat up. You need to drive enough with enough slip action of the torque convertor to heat up the transmission oil. Stop and go traffic is best.

Salim

fixdrive

Thank you, Salim. The readings for converter as 24.5F is way too low as it is below freezing mark. I am concerned whether I get the right data readings.

salimshah

My bad, I should have paid more attention to your post, Can it be a problem in the conversion of units C to F? Wish I knew more about the reader and the info sent by the OBDII when connected to the ECU which I think is running metric units [rx for Canadian market].

Salim

ukrkoz

I'd not be much relying on Torque for such diagnostic. Torque is limited to data it can pick up from sensors avaailable and, transmissions are normally well gusrded devices and require special equipment to access their data.Like Techstream.

fixdrive

Thank you ukrkoz and Salim.
I figured it out at the end. I had to read specs for CAN bus to understand OBD query responses. I will outline it below as it might save time for others in case they encounter the same issues.
Torque Pro is a useful application. However it is not handling well responses from my 2010 RX 350. I had to send requests for PID 2182 (year 2010+) and PID 21D9 (prior to 2010) as Torque was showing me values for both of them and I was not sure what is the correct one.
Both of these PIDs are for automatic transmission temperature.
On request 21D9 ECU was responding 7E8037F2112. It means that that the request is not recognized. According to CAN bus specs the last byte is supposed to be 31h but Lexus returns 12h for some reason.
Request for 2182 returned 7E904618251E0 meaning that it is a SAE Standards PID response (7E9h) with 4 additional bytes (04h), it is query of enhanced data by offset (61h = 40h+21h), PID 82 (82h) AT temperature in my case, byte 0 is 0x51 (A for Torque equation), byte 1 is 0xE0 (B for Torque equation). Thus the response to Transmission fluid pan temperature in Celsius request returned value 51E0h. Using equation (((A*256)+B)/256)-40) gives me my temperature as 41.875 Celsius which is 107.375 Fahrenheit.Since the response does not contain byte 2 and 3 I don’t have converter temperature. It is not necessary for me. May be it is supported by another request.
I hope it helps.

afpj

Where did you find those PIDs? I cannot find a toyota predefined set when I search in torque app. Did you create those PIDs manually? I am a little confused since the PID number (2182) is the same but different formulas for converter vs pan temp as in your first post.

Thank you for any clarification you can give.

N4TECguy

Would also love to have a list of Toyota specific PIDs!

fixdrive

These PIDs are not predefined in Torque Pro as they are manufacturer specific. I found Toyota PIDs by browsing this and other forums. See this link for 4Runner PIDs: http://www.toyota-4runner.org/5th-ge...orque-app.html
I would love to have PIDs for my RX350 but I had to refer to Toyota guys and follow try and error approach. May be TIS site has it. I would like to hear if someone was using it before.
About Transmission Temperature query 2182:
- This PID code if for years 2010+
- Reply contains information from all transmission temperature sensors. Each sensor temperature reading is represented by 2 bytes, 1 byte for the whole part and 1 byte for the fractional part. If my Lexus ECU had info about the convertor temperature the reply would contain 4 bytes for temperature readings and not 2 as in my case. For example, 4Runners get 2 sensors readings, pan and convertor. That's why you will find the same PID (query) for 2 different temperatures. One temperature will have A and B in formula, another one C and D and so one. I guess Torque Pro assign A to byte 0, B to byte 1, C to byte 2 of the specified parameter. See a short reference in Wikipedia on OBD and CAN bus format: https://en.wikipedia.org/wiki/OBD-II...it)_bus_format
- The formula in my first post converted the obtained data into Fahrenheit. The one that I stated in post #6 is in Celsius.

I hope it explains it all. Good luck!

afpj

I tried both formulas 2182 and 21d9 formulas, and looked at the 4 runner site you linked (pretty much same formulas) and cannot get any sensible readings. Values jump from negative to positive numbers. I have 2010 Rx built june 2009. Any advice is appreciated. thanks
.

fixdrive

Do not despair, I have the same car (RX 350 2010 produced in 2009) and I will help you out.
Torque Pro has a defect but there is a way out in figuring out your transmission temperature. Here are the steps as I was able to come up with:
1. Create a PID for 2182 reading only A and B (byte 0 and byte 1 of the data). Use formula for Celsius or Fahrenheit as I specified in the previous posts. It won't matter because we won't be using them directly. Instead we will use this PID to get a response from ECU of your vehicle.
2. Establish connection to the ECU via your WiFi or Bluetooth transmitter (dongle).
3. Run test for your PID.
4. In the test window you will see something like that :
Response:
7F2112
618253C0
The first line is actually a response from ECU that indicates an error. Torque Pro cuts it out. The full response is actually 7E8037F2112.
The second line is the response you need. I marked last 2 bytes in red colour as they indicate the temperature in Celsius in hexadecimal format. First byte (53) is a whole number, second byte (C0) is a fraction.
5. Process these 2 bytes in the following manner to get your temperature
5.1 A = 53h = 83 in decimal (5*16 +3), B = C0h = 192 in decimal (C = 12, 12*16 +0)
5.2 Calculate temperature in Celsius (A*256+B)/256-40 = ( 83*256 + 192)/256 - 40 = 43.75 Celsius
5.3 Convert to Fahrenheit in case your are more comfortable with this scale. Here temperature of 43.75 Celsius is 110.75 F.
5.4 Note that the second byte (byte 1) is a hexadecimal fraction of Celsius. If you don't need this precision and OK with readings of temperature precise to 0.. 1.6 C (0.. 2F) then you can just use the first byte. Just covert the byte into decimal format and subtract 40. Following the example 53h is 83, subtracting 40 gives us 43 C which is 109.4 F.

Practical example
I want change transmission fluid in my transmission pan (drain and refill). How to measure the correct level?
The answer: the correct level should be measured at 104 F (40 C) temperature of the fluid. The data obtained from ECU by Torque Pro must be 61825000 because value 50h in byte 0 corresponds to 40 Celsius (104 F) : 50h is 80 decimal, subtracting 40 gives 40.

Good luck and have fun!

afpj

Thanks for the explanation. I understand how this works now in theory. However I think I have a problem with the sensors in the vehicle itself. Looking at the test data, the variables come back with alternating values hence the alternating temperatures. The results after going through the equation is -40 to positive 119 degrees (after sitting for a few hours off) while coolant temp sits at 122°F. I don't understand why the values keep flipping. While the engine was running earlier today, it look like three results were being shown, negative 40 or so, positive 180 or so and 300 and something. No matter I used the 2182 or the 21d9, the results would flip around between negative and positive numbers so I suspect? an issue with my bafx elm327, or vehicle sensor. All other values that I monitor seems steady and do not flip around so I'm not entirely sure what to make of it.

fixdrive

Example of response to 2182 command.
The values keeps flipping because Torque Pro is confusing an error with the real data. On the request 2182 your car responds from two ECUs. One returns an error and another one the real data. Your WIFI or Bluetooth dongle sends these two replies to your phone application Torque. The app tries to read data from the error message and shows nonsense. In a different attempt the order might change and first comes the correct response from the second ECU followed by an error from the first ECU. Torque Pro reads again and this time it is the correct data. It confused me initially as well.
The error does not mean that anything wrong with your first ECU. It is just a response from that ECU that it does not support the requested command.
So to check the transmission temperature go to PID Editor and run <TEST> of your 2182 PID. This sends 2182 request to your car ECUs. Observe the response in the <Testing PID> dialogue and translate it to Fahrenheit or Celsius as I described previously. I attached a screenshot from my phone from the time I was figuring this all out last week. The data is circled in red. Ignore <Equation steps> in that dialogue.
Worst case send me your <TEST PID> screenshot. I will check whether both ECUs return error. To be on the safe side take readings when your engine is running even though I think the ignition ON is sufficient.

afpj

If the flipping values are normal behavior, then I can accept that. I'm also confused at seeing various iterations of the formulas seem to use different variables depending which Toyota forum I'm reading. For example, I've seen 2182 use variables A&B for the pan temp, C & D for the TC out temp, but I've also seen 2182 use E& F variables. Thanks again for your detailed response. When I get back from work next week I'll check the TEST results.