Copyright © 1998 General Motors Corp. 7–1
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
7–1. INPUT FUNCTIONS
Input functions are signals sent into the ECU that prompt the ECU to take action. Input functions are activated and
deactivated by switched ignition power or ground (wire 161B) to the ECU (wired through the VIW), or through the
MODE
button on the shift selector. The following input functions can be activated using the
MODE
button:
•
Secondary Shift Schedule
•
PTO Enable
•
Auxiliary Hold
•
Automatic Neutral for PTO (Special) (Refuse Packers only)
•
Manual Lockup (Oil Field only)
The wiring schematic in Appendix J illustrates installation requirements for input functions and designates specific wire
numbers in the transmission control system to be used for the activation of these input functions. However, in earlier
versions of the Allison WT Controls, specific wire numbers were not assigned to each input function. For example, the
control for the PTO Enable may have been on wire 118 in one calibration, but on wire 153 in another calibration.
Therefore, the wiring schematic in Appendix J should be used for reference only. Ask the vehicle manufacturer which
input functions are programmed, which wires are used, and whether voltage input was positive or ground. The
Pro-Link
®
9000 can also be utilized to determine which wire was programmed for a particular input function and the
wiring schematic can be consulted to find out if input to the ECU is + or – voltage. Refer to the Pro-Link
®
9000
diagnostic tool Operator’s Manual for further information regarding special input functions and other inhibits.
NOTE: The schematic in Appendix J shows the intended use of the control features specified. These features
have only been validated in the configuration shown. ANY USE OF THESE FEATURES WHICH
DIFFERS FROM WHAT IS SHOWN IS NOT THE RESPONSIBILITY OF ALLISON
TRANSMISSION.
Activating an input function can inhibit transmission operation in the same manner as diagnostic code. Use the Pro-
Link
®
9000 to verify an active input function or a diagnostic code inhibit. Refer to the Pro-Link
®
9000 diagnostic
tool Operator’s Manual for further information regarding special input functions and other inhibits. Also, for more
detailed information on input functions, refer to the Sales Tech Data Book “WT Controls and General
Information.”
The maximum number of input and output functions which may be used in any installation depends upon the
transmission model, its features, and the transmission control system. Refer to Table 7–1.
CAUTION:
Never use chassis ground as an
INPUT FUNCTION
ground. Chassis ground can carry
voltage potential of 1V or 2V above battery ground. This non-approved input will
“confuse” the ECU and cause erroneous input results.
Table 7–1. Input/Output Function Availability
Transmission Model and
Controls System Level
Auxiliary Transmission
Controls Functions
Number Of Input
Functions
Number Of Output
Functions
6-Speed, Non-retarder
Basic ECU
None 8 + Mode Button 3
6-Speed, Non-retarder
Max-Feature ECU
None 8 + Mode Button 5
6-Speed, Retarder
Max-Feature ECU
Retarder 6 + Mode Button 3
7-Speed (MD 3070PT)
Max-Feature ECU
Transfer Case 7 + Mode Button 3
S
ECTION
7 — INPUT AND OUTPUT FUNCTIONS
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