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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission - Diagnosis - 4L80-E >> Diagnostic Charts >> Code 87 - High Ratio >> Notes

Code 87 - High Ratio: Notes

Fig 1: Code 87 Circuit Diagram
G92C14128Courtesy of GENERAL MOTORS CORP.

Code 87 will set under following conditions: vehicle speed is greater than 7 MPH, TPS value is more than 25% of total TPS travel, 3rd or 4th gear operation is requested by PCM/TCM, and transmission ratio indicates 1st or 2nd gear. All conditions must be met for 6 seconds.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. This step checks if PCM/TCM can control solenoid "B".
  2. Battery supply should be present at PCM/TCM.
  3. This step checks shift solenoid "B" and circuits inside transmission for shorts.
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