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Home >> GMC >> 1992 >> Forward Control 7.4 N >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Transmission >> Component Check Charts >> Code 85, Undefined Ratio >> Notes

Code 85, Undefined Ratio: Notes

The PCM/TCM calculates the actual gear ratio from input and output speed readings while in each gear, then compares these to what the gear ratio should be, taking into consideration the selected gear range. This monitor includes Reverse gear, but does not include Overdrive gear.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This test verifies the proper function of the input sensor.
  2. This test verifies the proper function of the output sensor.
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