General Description

1. GENERAL DESCRIPTION
The F4AC1 automatic transaxle are a conventional transaxle in that it uses hydraulically applied clutches to shift a planetary gear train. However, the electronic control system replaces many of the mechanical and hydraulic components used in conventional transaxles.

2. FUNCTIONAL OPERATION
The F4AC1 automatic transaxle is a fully adaptive electronic control system. This system performs its functions based on continuous real-time sensor feedback information. The control system automatically adapts to changes in engine performance and friction element variations to provide consistent shift quality. The control system ensures that clutch operation during upshifting and downshifting is more responsive without increased harshness.

The Transaxle Control Module (TCM) continuously checks for electrical problems and some hydraulic problems. When a problem is sensed, the control module stores a diagnostic trouble code. All but 32 of these codes cause the transaxle to go into "limp-in" or "default" mode. While in this mode, electrical power is taken away from the transaxle via the TCM, de-energizing the transaxle control relay, and taking power from the solenoid pack. When this happens, the only transaxle functions are:
- PARK and NEUTRAL
- REVERSE
- SECOND GEAR

No upshifts or downshifts are allowed. The position of the manual valve alone allows the six ranges that are available. Although engine performance is seriously degraded while in this mode, it allows the owner to drive the vehicle in for service.
2-1 Overdrive (OD) off switch

The OD off switch is mounted on the gear select. With the gear select in D and the switch depressed (on), fourth gear is disabled but the same shift schedule is maintained gears 1, 2, and 3 are used only. Fourth gear can be overridden, but only under severe conditions; i.e., transaxle overheating.

3. DIAGNOSTIC TROUBLE CODES
Always begin by reading the diagnostic trouble codes using the scan tool. This procedure begins with INSPECTION CHART FOR DIAGNOSTIC TROUBLE CODES. This test will direct you to the specific test(s) that must be performed. If more than one trouble code exists, diagnostic priority should be given to the most recent code.

Each diagnostic trouble code is diagnosed by following a specific testing sequence. The diagnostic test procedures contain step-by-step instructions for determining the cause of a transaxle diagnostic trouble code. Possible sources of the code are checked and eliminated one by one.