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Home >> GMC >> 1987 >> Forward Control 7.4 W, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 17 (Engine Controls - Tests W/Codes - 7.4L) >> Trouble Code Charts >> Code 42 - Ignition Control >> Diagnostic Aids

Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Suburban, 1994 GMC Rally Camper Special, and 1994 GMC Rally. However, it is still accessible from the selected car via links, so may be relevant.

The scan tester cannot help diagnose a Code 42 problem. See INTERMITTENTS in appropriate TESTS W/O CODES article in the ENGINE PERFORMANCE section.

Fig 1: Code 42 Schematic ("P" Series A/T) Ignition Control
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Fig 2: Code 42 Schematic ("G" Series) Ignition Control
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Fig 3: Code 42 Schematic ("P" Series M/T) Ignition Control
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Fig 4: Code 42 Flow Chart Ignition Control
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