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 (2.5L) Electronic Spark Timing

Fig 2: Code 42 Schematic (All W/ 4L80-E Transmission) Electronic Spark Timing

Fig 3: Code 42 Schematic (3.1L) Electronic Spark Timing

Fig 4: Code 42 Schematic (All W/O 4L80-E Trans. Except 2.5L, 3.1L & 4.3L Turbo) Electronic Spark Timing

Fig 5: Code 42 Schematic (4.3L Turbo) Electronic Spark Timing

Fig 6: Code 42 Flow Chart Electronic Spark Timing