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Home >> GMC >> 1995 >> Forward Control 7.4 N >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 7.4L >> Trouble Code Charts >> Code 86, Low Gear Ratio Error >> Notes
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Code 86, Low Gear Ratio Error: Notes

Control module calculates ratio based on transmission input speed and output speed sensor readings. Control module compares known ratio to calculated ratio.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. An out-of-calibration transmission range pressure switch could falsely indicate actual transmission range.
  2. This test verifies proper ratio.
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