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HOMESERVICE MANUALSGMC1995SUBURBAN K2500, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 131 (ENGINE CONTROLS - BASIC DIAGNOSTIC PROCEDURES - 4.3L)ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECKTHE OBD SYSTEM CHECK DETERMINES
1995 GMC Suburban K2500, 6.5 F

The OBD System Check determines

1995 GMC Suburban K2500, 6.5 FSECTION The OBD System Check determines
WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 1996 Chevrolet Chevy Van, 1995 GMC Vandura, 1995 GMC Sonoma, 1995 GMC Safari, and 1995 GMC Rally. However, it is still accessible from the selected car via links, so may be relevant.
  • If Malfunction Indicator Light (MIL) works.
  • If PCM/VCM is operating and can recognize a fault.
  • If any Diagnostic Trouble Codes (DTCs) are stored.

After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the OBD system circuit check, if no codes are indicated and driveability problems still exist, see TESTS W/O CODES article and SCAN TESTER usage in TESTS W/CODES article.

  1. Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to A-1, MALFUNCTION INDICATOR LIGHT (MIL) .
  2. Turn ignition off. Install Tech 1 scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to A-2, NO SCAN TOOL DATA .
  3. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts and dies, see A-3, NO-START DIAGNOSIS. Repair as necessary.
  4. Using scan tool, observe DTC status LAST TST FAIL function. If any DTC is stored, save freeze frame and fail record information using CAPTURE INFO feature. If a DTC is indicated as last test failed, diagnose affected DTC. See TESTS W/CODES article. If DTC is not indicated, go to next step.
  5. Using scan tool, display DTC fail records. If a DTC fail record is stored, save freeze frame and fail record information using scan tool CAPTURE INFO feature. If a fail record is stored, diagnose affected DTC. See TESTS W/CODES article.
Fig 1: Data Link Connector Circuit Schematic (OBD)
G95D27360Courtesy of GENERAL MOTORS CORP.
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When to See a Mechanic

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

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