Diagnostic Aids

1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Diagnostic Aids

Using "SCAN" tool, observe block learn values at different RPM and airflow conditions. "SCAN" also displays the block cells, so the block learn values can be checked in each of the cells to determine when Code 45 may have been set. If the conditions for Code 45 exist, the block learn values will be around 115.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.