Code 42 - Electronic Spark Timing

Code No. 42 will set if an open or short to ground exists in the EST or by-pass circuit.

1. This ensures code No. 42 exists.
2. This checks for EST ground path through ignition module.
3. When high voltage touches circuit No. 14, module should switch. This causes ohmmeter to "overange" if meter is in the 1000-2000 ohm range. If positioned on the 10,000-20,000 range the reading will exceed 5000 ohms. Ensure module has switched.
4. If module fails to switch, check for short in circuit No. 13, open in circuit No. 14 or faulty ignition module or connections.
5. This ensures that code No. 42 is caused by a faulty ECM and not an intermittent in circuits No. 13 or 14.

Fig 1: Flow Chart - Code 42, Electronic Spark Timing

Courtesy of ISUZU MOTOR CO.