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Home >> GMC >> 1992 >> Value Van 4.3 Z, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Ignition System >> Timing Control Systems (C-4 & C-5) >> C-4, Electronic Spark Timing (Gasoline Engines)

C-4, Electronic Spark Timing (Gasoline Engines)

An open or short to ground in the Electronic Spark Timing (EST) or by-pass circuits will cause ECM to turn on SERVICE ENGINE SOON light and confirm fault causing Code 42 is present. Refer to G - GAS - TESTS W/ CODES article.