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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 68 - Overdrive Ratio Error >> Notes

Code 68 - Overdrive Ratio Error: Notes

Fig 1: Code 68 Circuit Diagram
G92E14112Courtesy of GENERAL MOTORS CORP.
NOTE: Test numbers refer to numbers on diagnostic chart.
  1. Code 68 will set under following conditions: transmission is not in Park or Neutral, TCC slips in 4th gear, transmission is in 4th gear, and TCC is locked on. All conditions must be met for 2 seconds.
  2. This step checks transmission signal being sent to PCM/TCM.
  3. This step checks for engine RPM signal being sent to PCM/TCM.
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