Preliminary Inspection

• Verify on-board diagnostics are working by performing DIAGNOSTIC SYSTEM CHECK -- ENGINE CONTROLS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.
• Ensure PCM and MIL functions properly.
• Ensure no DTCs (except intermittent) are stored.
• Ensure fuel control system operates properly. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.2L BRAVADA, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.
• Perform fuel system pressure test. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.2L BRAVADA, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.
• Visually inspect all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. See SYMPTOMS  .