Diagnosis - 4-Speed: Description: Introduction

Automatic transmission is electronically controlled. Transmission shifting and torque converter lock-up are controlled by Transmission Control Module (TCM).

The TCM receives information from various input devices and uses this information to control No. 1 and No. 2 solenoids on transmission valve body for transmission shifting and lock-up solenoid for torque converter lock-up.

An Overdrive (OD) switch is mounted on shift lever. When OD switch is depressed to ON position, transmission will shift into 4th gear when shift lever is in "D" position, and OD OFF light on instrument panel will go off. When OD switch is released to OFF position, transmission will shift into 3rd gear, and OD OFF light on instrument panel will come on. The OD OFF light is located on instrument panel.