Theory Of Operation

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This diagnostic checks for the number of unexpected Neutral disengagements occurring during a trip without receiving a control signal to disengage from the Transmission Controller Module (TCM). The Neutral gear is engaged when the four gear actuators are in the middle stable neutral position. If one or more of the gear actuators is not exactly in the middle neutral stable position the Neutral gear is disengaged. The total number of gear engagement control actions and the number of unexpected Neutral disengagements during a trip are accumulated in the internal memory of the TCM. The two separate registers in the internal memory which contain these counters are cleared after every trip. When the accumulated number of the unexpected Neutral disengagements during a trip is greater than a threshold, this diagnostic will be considered failing.