General Diagnosis Information

The TCU used with the AW-4 transmission has a self-diagnosis feature programmed into it. The diagnosis program is compatible with the MS 1700 tester.


The AW-4 is an electronically controlled transmission. Shift points and sequence in the forward gear ranges are controlled by the TCU. Before attempting repair, it will be necessary to determine if a malfunction is related to electrical or mechanical components.


The MS 1700 tester will identify faults in the electrical control system. The road test, pressure test, stall test and time lag test plus the general diagnosis charts will help locate faults in the mechanical running gear.


All AW-4 diagnosis should begin with the Preliminary Check Procedure. The procedure is designed to help identify the type of problem (mechanical/electrical) that has occurred. The first step of the procedure is the Initial Inspection and Adjustment phase which is detailed in this section.