Intermittent ABS Light/ABS Code 46 - Explanation and Fix

This post is being made for posterity, A.K.A. the next guy who has to deal with this issue.

Code 46 was not listed in the resources I was able to dig up myself.

This is a simple issue once you have it figured out, and I've done my best to present the info in an easily accessible manner. That being said, please post any questions or suggestions for presentation and I will update this post.

Vehicle:
2nd Gen Tacoma and many other Toyota vehicles

Issue:
Failed/failing stop light switch (Toyota P/N: W0133-1773206, many OEM/aftermarket available). Replacement is inexpensive, easy, and requires no tools.

Symptoms (one or more):
- Intermittent ABS light on dash
- AND ABS code 46 (see Notes below)
- AND POTENTIALLY Difficulty shifting out of park

Explanation:

Spoiler: Explanation of issue:

The ABS system looks for a signal from the Stop Light Switch (SLS), which is mechanically connected to the brake pedal inside the cabin, within a certain amount of time from that the ABS system detects the brakes being applied. When the SLS is dirty, worn, or obstructed by foreign material, it will begin to fail intermittently and cause the ABS system to disengage until the next time that it detects a correctly timed signal from the SLS.

Failure of the SLS can also cause the vehicle to refuse to shift from Park, since the system relies on the SLS to indicate that the brake pedal is depressed.

The reason that door-kicking the brake pedal will sometimes turn the light off (after a short delay) and turn off the ABS light/allow the vehicle to shift is that the sharp blow can sometimes get a good enough signal from the switch to temporarily appease the system.

Diagnosis:
- ABS light on dash is intermittent, and does not seem to be related to driving conditions, temperature, or other external factors
- If the ABS light is lit when the vehicle is turned off, and the ABS codes are checked (see Notes below), code 46 is presented
- POTENTIALLY: Vehicle will intermittently not shift out of park when started and brake pedal depressed
- POTENTIALLY: A hard, sharp kick to the brake pedal while the vehicle is stationary turns off the ABS light after a delay and may also allow the vehicle to shift out of park.

Solution:
- Sometimes a few hard, sharp kicks to the brake pedal while the vehicle is stationary will remove foreign material obstructing proper operation of the SLS and allow normal operation for an indeterminate length of time.
- Potential easy/temporary fix: Remove existing SLS (see Notes below), examine for foreign material, clean with electronics contact cleaner, and replace
- Preferred fix: Remove and replace SLS - this is an inexpensive part and takes 2 minutes to replace with no tools

Notes:
Checking ABS Codes w/o a reader:

Spoiler: ABS Code Check Procedure

1) Turn off the vehicle while the ABS light is on.

2) Use a paperclip, piece of wire, or pin jumper to connect the two indicated pins (4 and 13) on your ODB-II port, found under the dash on the left side as viewed from the driver's seat.




In the future, if the above image fails to load, simply search for a picture which shows the pin numbers for an ODB-II port.

3) Turn the vehicle on, and count the blinks from the ABS light on the dashboard. Any ABS error codes will be displayed sequentially with flashes of the ABS light, with a short pause between digits of each 2-digit code, and a long pause between codes.

For example, if we represent the light being "on" with an X, and "off" with a -, you might see something like:

X-X-X-X---X-X-X-X-X-X------X-X-X-X---X-X-X-X-X-X------X-X-X-X---X-X-X-X-X-X

Indicating a repeating ABS code of "46". If there are multiple ABS error codes, they will display sequentially and repeat, for example:

X-X-X---X------X-X-X-X---X-X-X-X-X-X------X-X-X---X------X-X-X-X---X-X-X-X-X-X

Indicating error codes "31" and "46" at the same time.

Tacoma Stop Light Switch access/replacement:
This video is specifically for a 4runner, but the parts are the same and so is the location and procedure:
https://www.youtube.com/watch?v=3Sja-CXlfBo