Diagnostic Aids

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana Special, 2001 GMC Savana Camper Special, and 2001 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.

DTC U1301 cannot be retrieved as current. Diagnosis for current DTC U1300 is accomplished using TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICEΒ  under SYSTEM TESTS. An intermittent condition can be caused by a short to voltage on the class 2 serial data line.

RENDER: 1.0x

NO RELATED

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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.