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Home >> GMC >> 1987 >> Forward Control 4.8 T, Standard >> Repair and Diagnosis >> Engine Performance >> System >> CCC TBI Tests W/Codes >> Diagnostic Charts >> Manual Transmission Shift Light Check >> Test Description
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Test Description

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This should not turn the shift light on. If light is on, there is a short to ground in circuit No. 456 wiring, or a fault in the ECM.
  2. This should turn shift light on.
  3. This check for an open in the shift light circuit, or a faulty ECM.
Fig 1: Manual Transmission Shift Light Check Flow Chart
G120860
Fig 2: Manual Transmission Shift Light Check
GB0048334
Fig 3: Manual Transmission Shift Light Check Schematic
G120859