Engine Control System - Trouble Shooting - No Codes - 4.2L: INTERMITTENTS: Preliminary

Perform the Diagnostic System Check-Engine Controls before starting. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.