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Code 87, High Gear Ratio Error - All Models: Notes

WARNING: This page does not describe the selected car, but rather 19 other vehicles, including the 1996 Chevrolet Chevy Van, 1995 GMC Vandura Special, 1995 GMC Vandura, 1995 GMC Sonoma, and 1995 GMC Safari. However, it is still accessible from the selected car via links, so may be relevant.

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

  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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