Diagnostic Aids

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

Fig 1: Code 42, Schematic, Electronic Spark Timing

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 42, Schematic, Electronic Spark Timing (4.3L)

Courtesy of GENERAL MOTORS CORP.

Fig 3: Code 42, Flow Chart, Electronic Spark Timing

Courtesy of GENERAL MOTORS CORP.