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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 86 - Low Ratio >> Notes

Code 86 - Low Ratio: Notes

Fig 1: Code 86 Circuit Diagram
G92A14126Courtesy of GENERAL MOTORS CORP.

Code 86 will set under following conditions: vehicle speed is greater than 7 MPH, TPS value is more than 25% of total TPS travel, 1st or 2nd gear operation is requested by PCM/TCM, and transmission ratio indicates 3rd or 4th 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".
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