Code 42, Elect Spark Timing W/Dis: Notes
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 1990 Pontiac Grand Am, 1990 Pontiac 6000, 1990 Oldsmobile Cutlass Cruiser, 1990 Oldsmobile Cutlass Ciera, and 1990 Oldsmobile Cutlass Calais. However, it is still accessible from the selected car via links, so may be relevant.
Code 42 indicates the ECM has seen an open or short to ground in EST or by-pass circuits (DIS ignitions).
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- This test confirms Code 42 and determines if fault is hard or intermittent.
- 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.
- 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".
- 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.
- This step confirms that Code 42 is a faulty ECM and not an intermittent problem in circuits No. 423 and 424.