4R55E OBD transmission fluid temperature sensor | Ford Explorer Forums - Serious Explorations

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4R55E OBD transmission fluid temperature sensor

manimal

Well-Known Member
Joined
June 27, 2006
Messages
144
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13
City, State
Gig Harbor WA
Year, Model & Trim Level
96 XLT
I recently purchased a BAFX OBDII bluetooth adapter and got Torque Pro going on my Android phone. Everything is working great, and once I loaded the Ford specific OBD PIDs, I was able to get transmission fluid temperature readings in the app - awesome!

However I'm wondering at what location is the temperature measured? Is it polling fluid temperature within the pan, or at the cooling lines?

Additionally I see that there are a handful of DTCs associated with the 4R55E transmission temp sensor. I don't mean that I have these DTCs - I just see that they exist in a list of possible DTCs.

What does the ECU do with this information? Does the trans temp affect how it shifts the trans?

Frankly it really surprises me that if this reading is available to the ECU, it isn't something that is included in the gauge cluster - at the very least as a warning lamp if the trans is overheating. Typical bean counter stuff I bet.
 



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Not sure which item from the following list is actually implemented in the rather ancient transmissions used in 2nd gen Explorers, but here it goes (from Wikipedia):
This sensor determines the fluid temperature inside the transmission. This is often used for diagnostic purposes to check ATF (Automatic Transmission Fluid) at the correct temperature. The main use of this has been as a failsafe feature to downshift the transmission if the ATF becomes extremely hot. On more modern TCUs this input allows the TCU to modify the line pressure and solenoid pressures according to the changing viscosity of the fluid based on temperature, and also to determine regulation of the torque converter lock-up clutch.

In addition, I learned that some transmissions (again, no idea about the ones used in our generation X) will lock the TCC if possible when the temperature is excessive. Locking the TCC eliminates the heating caused by slippage in the torque converter.

I recently purchased a BAFX OBDII bluetooth adapter and got Torque Pro going on my Android phone. Everything is working great, and once I loaded the Ford specific OBD PIDs, I was able to get transmission fluid temperature readings in the app - awesome!

However I'm wondering at what location is the temperature measured? Is it polling fluid temperature within the pan, or at the cooling lines?

Additionally I see that there are a handful of DTCs associated with the 4R55E transmission temp sensor. I don't mean that I have these DTCs - I just see that they exist in a list of possible DTCs.

What does the ECU do with this information? Does the trans temp affect how it shifts the trans?

Frankly it really surprises me that if this reading is available to the ECU, it isn't something that is included in the gauge cluster - at the very least as a warning lamp if the trans is overheating. Typical bean counter stuff I bet.
 






Interesting.

I was also surprised to see that the ECU in the 96 provides real time output of torque converter slip RPM (to verify lock state) and current transmission gear.

Really surprising the amount of info that is available on what is otherwise a pretty old OBD2 system.

It would have been cool if Ford had included a transmission temperature gauge as part of a towing package with the Explorer/Ranger series.

Now I need to check out Car Gauge Pro, which apparently does ABS codes - I have an intermittent ABS light that seems to make no sense, and no local shops are willing to read ABS for free.
 












After a 15mi drive back from Home Depot with around 600lb of sand and lumber in the back. Looking Good!

It's very satisfying to be able to watch the TC lockup status and current gear. Confirms some stuff I thought the truck was doing during certain situations

icOIy3t.png
 






Interesting. I just set up Torque Pro with the Torque Scan add-in on my 98 XLT SOHC. There was no data available for the transmission temperature or the oil temperature. Is there an add-in I need to download? Are there other PID's available for this vehicle?
 






Yes. Once you add the Ford specific PIDs, you'll see several available PIDs for transmission fluid temp. One of them should work.

Go to Settings -> Manage additions PIDs > press android menu button > Add predefined set > Ford
 






What all kind of temp readings can you get with that thing? I might pick one up...
 






Depends on year, but on the early OBDII Explorers, trans temp is one of the most important.

The sensor will read the ECU coolant temp sensor, intake/ambient air sensor. You may also have catalyst temp on the late 90s Explorers..

Other interesting data includes torque converter slip rate, current trans gear, MAF CFM, manifold vacuum, speed, and calculated average MPG - surprisingly the Gen 2 and up Ford ECU does calculate its own average MPG but the data was not made available in a built-in screen like it is in many newer vehicles.

Even on my 96 it has available data for individual cylinder misfires and fuel trims, you can spot ignition or fuel issues early on.
 






I have a 1999. I would like this for long trips across country on the highway. Being able to read all my fluid temps would be very helpful in knowing how far and long I can drive at on point and time.
 






I bought one.. Any one of those cheap android tablets and a cup holder for the tablet. I think this is a great post on the product and appreciate you bringing it to my attention. Even though this wasn't the intended reason for the post I still thank you. I will post pics when everything comes in.
 






I have a really cheap Chinese Android 4.4 tablet (on sale last year Amazon $50) that I bought for our son, it has BT but not sure how reliable it is. I may pair it up just so I can see.

I have also been thinking of buying a cheap small Chinese note/tab specifically for the BT OBD reader.
 






Yeah exactly I bought one of those generic 4.4 quad core w/ bluetooth. Pretty much all the same. I got mine off ebay for $34 bucks. I cant beat that. Now with the OBD2 scanner and setting it up next time, Would like to have a full readout at all times of whats going on. Alot easier then installing a bunch of gauges everywhere.

And that doesn't even include the whole code reading and scanning. I think everyone should do this lol. Solid investment and now I can even help friends with their cars.
 






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