Intermittent Shift Problems

My 2018 Platinum w/ReadyLift 4/2, 35X12.5X20, Hypertech Speedo Calibrator, Toyo AT2 Extremes with 63K miles suddenly began demonstrating intermittent shift issues. It would seemingly hunt for gears and bog down, hard shifts, and in general, act like it was pushing a 80 MPH head wind. For 3 weeks I fought the issue and took it to the dealer twice. The first time, they flushed the transmission and in the report said it was shifting better. It wasn't so I took it back and asked them to perform mechanical tests as described in the Toyota Service Manual. They did and results were normal. So I took it to a local, highly respected transmission shop. They were able to reproduce what I was experiencing so I called the dealer and was asked to bring it in again and ride with a tech to show what was happening. Before the appointment I replaced the tires and had the truck aligned. It was barely out of spec. It rode nicer but didn't fix the issue. I also cleaned the MAF and throttle body. The transmission shop also said my battery failed the load test so I replaced the battery. Naturally, the battery replacement cleared the learned shift patters and reset. The battery replacement was the key. The ECM and ECT have power requirements that, if not met, will cause intermittent shift problems. So before you go through all the trouble I did, load test your battery, clean up the terminals and battery connections, and see if that doesn't address the issue. My truck is back to shifting perfectly. Please note that I also bought a scanner and monitored it regularly for DTCs and temps. All normal so you won't likely be able to detect the issue with a scanner.

 

That is good information; thanks. It’s crazy how many issues the batteries will cause on these trucks.

 

Was this your original battery? A dying battery can cause a plethora of odd issues that one wouldn't normally think is connected.

 

It was the original battery. Multi-meter showed 12.3 volts and no reason to suspect it was bad until the transmission shop load tested it.