I failed an emissions test by reason of “no voltage at the data link connector” three (3) days after using a jumper wire between terminals 4 and 13 to read ATF temperature. OBD scan devices draw power from terminal 16 (BAT) of the connector.

The OBD 7.5 amp fuse under the dash above the parking brake was blown and there is no spare in the fuse box of that size. I did not insert anything in the BAT terminal, so fuse failure appears to be unrelated to checking ATF temperature.

Amazon sells a Bussmann 6-piece low profile fuse assortment for $3.67 which is excellent quality at a price that is better than the dealer or any box store. Amazon.com: Bussmann (BP/ATM-A6LP-RP) ATM-LP Low Profile Fuse Assortment - 6 Piece: Automotive

The transmission operates better with Valvoline MaxLife in it. This was the first flush at 117,000 miles. Old fluid appearance and odor was normal for its age based on experience changing fluid in personal vehicles over the past 49 years. Never had a transmission failure or seal leak, knock on wood.

I thought Toyota said NOT to use any ATF but their own...

i did the full 13 quart atf drain and fill with maxlife atf at 70k and definitely noticed much smoother transmission shifts...

did the same with my camry at 75k and helped cure the hard trans slips and shifts

A few thoughts:

1. Bussman fuses have been around for over 80 years, probably longer. They are great quality. You can buy them anywhere, not just Amazon. Littlefuse the same.

2. Most cars now days are considered life time fill for the transmission, i.e. you never need to change the fluid. That is why there is no transmission fluid dip stick in most cars now days. Modern lubricants (synthetic) is what makes this possible.

3. If you do change the fluid, it is best to just drain, change filter, and refill. Never do a power flush for that stirs up sediment that can clog the fine passages.

Keep in mind, most car manufacturers consider “lifetime” to be somewhere around 100-125,000 miles. I would not leave the fluid in for longer than that.

Especially under heavy use.

The Warranty and Maintenance Guide lists additional maintenance items for special operating conditions (SOC) that includes driving on dirt or dusty roads, towing, using a car-top carrier or heavy vehicle loading. Under these conditions, Toyota recommends replacing automatic transmission fluid (ATF) every 60,000 miles. I occasionally operate on the borderline of SOC, therefore, I elected to replace ATF at 117,000 miles.

This information comes from a Lubrication website: “Clutches and friction bands within the transmission need friction to function properly. Friction modifiers are additives in ATF fluid to smooth transition from one speed to another, maximize efficiency and reduce slippage. Otherwise, the clutches and bands would “chatter,” causing damage and an irritating condition for the driver.”

Shifting is smoother after I changed the fluid, therefore ATF friction modifiers have been refreshed.

Transmission clutch packs wear and some of that material is exceedingly fine and largely remains in fluid suspension. Particle size is not large enough to bind close clearances. If sediment was present, then normal driving over a bump in the road, stop and go, and vehicle acceleration would stir up sediment. This transmission has a strainer to capture larger particles that may be present. The manual does not recommend replacing it. The strainer has a large surface area so that fluid flow is not impeded during normal operation and wear. If material clogs the strainer, then the clutch packs are worn out. Premature failure is likely to occur when the transmission is abused and/or fluid is not changed under special operating conditions.

I didn't do a power flush. I let the transmission pump move the fluid, which is exactly what it does when it circulates fluid with the system sealed and the vehicle driven. The first drain and fill is with the engine off. On subsequent drain and fills, I allowed the transmission pump to remove less than what the pan holds so that there is always some clean fluid in the pan.

Hey @DougR , why did you jumper those terminals together on the OBD2 connector? I thought you can read the trans fluid temp with an OBD2 dongle and a phone app via Bluetooth.

There’s a good tutorial and video here:
Comprehensive Guide to 5th Gen 4Runner Trans Service

I used a jumper wire given that it is an approved Toyota procedure. I looked into getting a dongle and using a phone app, however Amazon reviews on various products were mixed, so I didn't invest. I have no compelling reason to know ATF temperature while driving (no heavy towing, no off-roading).

I "correlated" the jumper method with an infrared reading on the pan and a simple "hold one's hand on the pan" method. Infrared was 2-3 degrees lower. It's very annoying for me to focus and wait for the "D" light indication to come on. I much prefer using the infrared thermometer to watch fluid temperature rising and when it's near the check level range, I then watch for the "D" light to come on.

I use an ODB Link dongle I bought from Amazon, and Torque Pro to get my transmission temps. I have dials set up in the app for converter temp and pan temp. It's useful for me, since I tow a trailer for camping with the Scout troop. OP said he didn't need the dongle, but it's been really useful, if only for peace of mind when towing.

As much as they would like that, they are not allowed to.
Per the Magnuson - Moss Warranty act, if a vehicle manufacturer requires the use of a specific filter or fluid, they must provide it to you free.

Whether you CHOOSE to use something else, hopefully an equivalent product, is your choice...

I've blown that fuse doing an ATF fluid level check. It's easier to do than you think. To avoid this issue, I bought an OBD connector(16 pins off ebay) and hard-wired 4 & 13. Now all I have to do it pull off the cover on the OBD plug and stick in my jumpered gadget.

Click on tacomaworld link below for a pic of the OBD jumper gadget - look around in post #199343

Cap City Build & BS AF | Page 9968 | Tacoma World

I was wondering if anybody else blew a fuse. You’re probably correct that I did it. Hard wiring an OBD connector is a good solution.