I've done plenty of reading and even more searching...

**Update**

It's been a while since I had this in front of the crew here and I wanted to add a little more information, even if it's only to help the next person down the line if I accidentally find a solution.

I spent about an hour under the truck a week ago with a bright light and a focus on wires and connectors. I ran every wire bundle from the engine compartment to the rear bumper. AGAIN. Since the last time I was in this forum, I spent quite a bit of time reading anything and everything about every suggestion that was made here earlier, and it only served to muddy the water for me. I learned about license plate light bulbs, fuses for backup lights, and a few other "fixes" that I would probably never have considered. The issues I started to read about were different than the ABS related discussion this thread was loosely focused on. Nothing was perfectly relevant.

Recently, I spent about 4 hours cleaning the truck. Like, scrubbed the front suspension and engine compartment with a scotchbrite pad and goof off type cleaning. I removed all wheels, both for cleaning and inspecting, and to check the pads and rotors. Found nothing obvious related to the ABS system. Again.

This Tuesday morning, I bit the bullet and took the truck to the dealer. I was brief and gave the service guy the best hand off I could come up with. He wrote, "CUST STATES CHECK ENGINE LIGHT ON DASH/VEHICLE LACKS POWER UPON ACCELERATION/CRUISE CONTROL IN/OP MULTIPLE MESSAGES/FAILURES CHK/ADV" I knew I couldn't overwhelm him with too much information and that he wouldn't be listening and/or adding much to the notes anyway. He gave me an estimate for $210 (an hour of diagnosis time) and told me to come back that evening. About four hours later I got the call. "Bad news. We need more time. Tech is making progress but he needs three and a half more hours. New estimate is $735" He talked to me a little about what the tech had shared with him and what I had already known regarding DTC. They were seeing the same errors and now wanted to check for rodent activity and chase wires. I felt trapped, but knew beforehand that they were going to take this chance to make as much money as possible, maybe regardless of what the actual cause of these issues was. I asked the service writer, "If I authorize this new estimate and he finds a loose connector after another hour, what happens to that extra $400?" There wasn't much I could do, as I was now 175 miles away and had zero progress toward a fix of my own anyway.

The next morning I drove down to the shop and asked the service writer for an update. "No fix yet. But the tech gave you more time than you paid for. He wants to try the transmission range sensor. New estimate is $1550."

I asked to speak to the tech and met the guy working on my truck. He explained to me how he used a couple specialized tools to do things like view the waveform of the signals running between computers and components, lifted the center console, etc. Mostly small talk until I started asking questions and adding context. He confirmed that the ECU error was the top of the problem pile (Like Tripleconpanna mentioned) and the real issue was most likely the trans sensor, especially after I shared the sluggish from a dead start symptom.

It was probably the tech who added notes to the service ticket - "verify customer concern found several dtc, dtc c1a50 brake system malfunction, p0705 transmission range sensor, c13a9 brake system malfunction, cleared codes dtc p0705 returned, inspected range sensor seems okay, will need diag time to performed resistance check and voltage checks to range sensor and ecu. FURTHER DIAG REC NEW RANGE SENSOR FOR TRANSMISSION"

I'm back to waking up thinking about what I haven't checked yet. The shifter knob is loose now, so I'm to the dealership in the morning to get that fixed before I'm gone again for a couple of weeks. I'm going to buy an OEM transmission range sensor and do the repair myself. Seems like the best price for a Toyota product is $175 local and ~$120 via the internet. I have the Chilton manual for the install and it looks relatively simple. I was a little confused when searching for the part and was wary about the differences between vendor descriptions of the same part number, so for those who care -

• Q: Why does Toyota continue to use the term PNP switch instead of TR sensor, despite SAE's recommendation on Toyota Sequoia and Toyota Tundra?
  A: Despite the Society of Automotive Engineers (SAE) recommending since 1996 that manufacturers use the term Transmission Range (TR) sensor instead of Park/Neutral Position (PNP) switch, Toyota persists in referring to the TR sensor as the PNP switch.

Thanks again to the masochists and the generous. I appreciate having a place to work this out and maybe learn something along the way.

 

I'm wondering if you have found a remedy to your problem? my truck has the same symptom's. And the D for drive doesn't light up in the dash when drive is selected (P, R, N, all light up when selected)