1987 Chevrolet Hi-Cube 6.2 J, 400/M40FACTORY OEM SERVICE PROCEDURE

Diagnostic Aids

"SCAN" tool reading should closely match speedometer reading with drive wheels turning.

See PARK/NEUTRAL SWITCH DIAGNOSIS chart if vehicle is equipped with automatic transmission.

If Park/Neutral switch is okay, see INTERMITTENT TROUBLE CODES in TROUBLE SHOOTING section.

Fig 1: Code 24 - Vehicle Speed Sensor Fault ("SCAN" Diagnostics)
G120813
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

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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.

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