Toyota A/T Parking Indicator Circuit Diagnostics Guide

Quick guide from the manual

This document provides diagnostic procedures for the A/T Parking (A/T.P.) indicator light circuit in Toyota Tacoma vehicles equipped with A340E or A340F automatic transmissions. The indicator light warns the driver that the propeller shaft and wheels are not locked when the transmission is in Park but the transfer case is in Neutral. If the light illuminates, the transfer shift lever must be moved out of the Neutral position.

Circuit Description

The system monitors the position of both the transmission shift lever and the transfer shift lever. When the transmission is in Park (P) and the transfer case is in Neutral, the propeller shaft and wheels remain free. The A/T.P. indicator light is designed to alert the driver to this condition.

Inspection Procedure

Follow these steps to diagnose issues with the A/T Parking indicator circuit:

1. Check Park/Neutral Position Switch: Inspect the switch according to the procedure on page DI-406. If the result is NG (Not Good), replace the switch.
2. Check Transfer Neutral Position Switch: If the first step is OK, inspect the transfer neutral position switch as per page TR-13. If the result is OK, replace the switch.
3. Check Combination Meter: If the previous steps are NG, inspect the combination meter (page BE-38). Repair or replace the meter if necessary.
4. Harness and Connector: If all components test OK, check and replace the wiring harness and connectors as described on page IN-28.