Code 42, Elect Spark Timing W/Dis: Notes

Code 42 indicates the ECM has seen an open or short to ground in EST or by-pass circuits (DIS ignitions).

1. This test confirms Code 42 and determines if fault is hard or intermittent.
2. This test checks for a normal EST ground path through the ignition module. If circuit No. 423 is shorted to ground, reading will be less than 500 ohms.
3. As test light voltage touches circuit No. 424, the module should switch. This will cause the ohmmeter to "over-range" if meter is in the 1000-2000 ohm position. A higher ohm range will indicate over 5000 ohms. This test assures that the module "switched".
4. If module did not switch, this step will test for a short in circuit No. 423, an open in circuit No. 424, and a faulty ignition module connection or module.
5. This step confirms that Code 42 is a faulty ECM and not an intermittent problem in circuits No. 423 and 424.