Diagnostic Aids

1995 GMC Suburban K2500, 7.4 NSECTION Diagnostic Aids

Scan tester displays APP No. 3 position in volts, and should display 4 volts with throttle closed and ignition on or engine at idle. Voltage should decrease at a steady rate as throttle is moved toward WOT. Also, 90 percent pedal travel is acceptable for correct APP operation.

Monitor APP No. 3 sensor while applying accelerator pedal with engine off and ignition on. Display should vary from about 4 volts with throttle closed, to about 2 volts with throttle at WOT.

Fig 1: DTC 63 Schematic (6.5L Diesel) Accelerator Pedal Position (APP) No. 3 Circuit High (Models With PCM)
G95A26955
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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.