Trans Temp Gauge

Does anyone know if I could splice the wires from an aftermarket digital transmission temperature gauge like this one from Jegs, Transmission Temperature Gauge LED Digital P/N 555-41462 into the wiring for the existing analog gauge and get an accurate reading?

 

IDK - but, probably not easily, if at all. For less that a 100 bucks you can add an Ultra gauge and monitor trans temps and a number of other parameters. I use one on my '07 to digitally monitor trans temps, charging system voltage, engine temp, and fuel consumption.

 

You could also get a veepeek and use the obd fusion app to monitor pretty much anything you can think of on your phone.

 

I haven’t made a listing for it yet, but I have a Scangauge2 I’ll be selling that monitors that and much more if you’re interested. Like the other options, it just stays plugged into the OBD2 port and you can mount it wherever you want.

 

I run both the veepeek and the ultragage at the same time with a splitter, Since i only check trans temps now occasionally after my trans cooler install. Its pretty convenient being able to have both plugged in at the same time.

 

I'm assuming that the sensor is a thermocouple mounted somewhere on the transmission and the the wires should be fairly easy to tap into near the sensor connection. I have a scan tool, but it doesn't show trans temp. Thought this gauge would be an inexpensive way to monitor the temp more accurately than the analog gauge and to do a drain and fill.

 

I think the veepeak is like 30 bucks. probably the cheapest way to go for you for trans temps.

 

Try it and be the first! What people above are getting at is the CANBUS gives an accurate reading which can be pulled from the OBD2 port, what the gauge signal actually is is unknown. Is the gauge just measuring resistance from the temp sensor? Is the gauge talking to the OBD2? Is there processing before the gauge to make the gauge "dumb" or is that done in the gauge? I don't know if anyone has the answer to those, and since it's easy to pull the data from the OBD2 port, not much motivation from others to look into it.

 

I'm assuming that the sensor is a thermocouple mounted on the transmission and that tapping into the wires near it shouldn't be too difficult. I have a scan tool but it doesn't show trans temp. Thought that this gauge would be an inexpensive way to monitor the trans temp more accurately than the analog gauge.

 

I personally don’t like the idea of tapping into the wiring anywhere, especially on ECU related wiring. That low voltage signal wiring can be very sensitive. Sounds like a CEL waiting to happen, especially as said connections begin to corrode over time. What kind of scan tool do you have? The scangauge 2 for example you just have to manually enter the correct pid for the trans temp and then it shows up which is what I did. Some other OBD2 gauges it populates trans temp automatically out of the box.

 

If you wanted to follow your plan as the solution you have to do a lot of foot work. And if done wrong, the engine and two temperature sensors in the trans will report incorrect info to the ECU. Why? The thee temperature sensors share common connections.

From the transmission pins 1 an 9 (brown and light blue) are the wires needed however, not all thermistors have the same resistance curve you can't just slap a gauge on there and have it read correctly in most cases. That is not to say it can't be done. It could but it will take some work.

This leads to options B and C. Use an App or add a whole separate system. Others covered the app so, now you're left with buy a gauge and sensor set and pull the pan and weld a bung in and slap a gauge in the cab somewhere otherwise you risk messing up critical data.

 

I was thinking that there be a chance that it would cause a trouble code, was checking to see if it had been done.

 

The factory instrument cluster gets the signal from the engine ecu on the CAN bus. I reversed engineered the signal and scaling.

The obd apps are another option as they ask for the data on the bus using OBD protocol.

Taping directly to the sensor might be an option but you would most likely have to read the resistance and scale accordingly. This would be reading in the signal sent to the Engine ecu

 

If I'd done a little research prior, I wouldn't have asked the question. Didn't realize that the temp sensor was inside the transmission. Thought it and its connection might be accessible. Thank you all for your input.

 

i think there are actually two temp sensor but both are inside the transmission. One may be down near the pan.