Toyota Tacoma: Transmission Diagnostic Guide

Diagnosing the transmission quickly on your Toyota Tacoma can end up saving you a lot of money. Read on to learn how to do it.

By Bassem Girgis - February 10, 2016

This article applies to the Toyota Tacoma (1996-2015).

The transmission is a very expensive component on your Toyota Tacoma. Sometimes, things can go wrong with it, and a lot of these times, it can be fixed if diagnosed correctly and quickly. It's recommended you diagnose any issue that comes up with your transmission as quickly as possible, because the longer you wait, the more you risk permanent transmission damage. If you're experiencing anything wrong or different with your transmission, read on to learn how to diagnose it yourself.

Toyota Tacoma Transmission Diagnostic Guide

Materials Needed

  • Flashlight
  • Rag

Step 1 – Check transmission fluid

It could be low or dirty.

The transmission fluid could burn faster if you drive your Tacoma roughly. If you do a lot of towing and hauling, you could be burning the tranny fluid faster, which would cause the transmission to heat up faster. Also, as transmission fluid ages, its lubricating additives begin to wear down, which could cause damage to the gears, as it stops lubricating. Check the transmission dipstick for the transmission fluid level and color. If it's low or if it's too brown, then you may need to add some or change it completely.

Toyota Tacoma transmission dipstick, location
Figure 1. Transmission dipstick.

If the transmission fluid is in a good condition, proceed to Step 2.

Step 2 – Check transmission wiring

They could be worn or cracked.

The transmission wiring could play a role in how the transmission feels. For instance, if the wires going to your transmission are worn, you could start feeling transmission slippage or delayed transitions. Slide under the truck with your flashlight, then inspect the transmission wires. While you're there, unplug the wires, and clean their plugs. Any disturbance in the wires could cause false signals to the transmission, which would cause the tranny to act up.

Toyota Tacoma transmission wires
Figure 2. Inspect transmission wires.

If the wires are in a good condition, proceed to Step 3.

Step 3 – Check OBD-II diagnostic trouble codes

It could lead you to culprit.

A scan tool can make your life a lot easier. If the problem is inside the transmission, it's in one of the many sensors attached to the transmission, or even if it's in the transmission cable, the scan tool can guide you right to it. Connect your OBD-II scan tool to the outlet under the dashboard. Then read the code it gives you. Write the code down and compare it to your owner's manual, and that should point right to the issue.

connecting scan tool in Toyota Tacoma
Figure 3. Connect scan tool to connection.

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