Code 42 - C(3)I Ignition

Code 42 indicates that the ECM has seen an open or grounded bypass or EST circuit with engine running.

1. 1) & 5) These tests check to see if the ECM recognizes a problem. If it doesn't set Code 42, problem is intermittent and could be due to a loose connection.
2. 2) With the ECM disconnected, the ohmmeter should indicate normal resistance of the ignition module (less than 200 ohms).
3. 3) This test checks if ignition module switches when the bypass circuit is energized by 12 volts through the test light. If the ignition module switches, the ohmmeter will read more than 8000 ohms.
4. 4) Disconnecting the ignition module should make the ohmmeter read as if it were seeing an open circuit. If the ohmmeter displays a low reading, circuit 423 is shorted to ground.

Fig 1: Flow Chart, Code 42: C(3)I Ignition

Fig 2: Flow Chart, Code 42: C(3)I Ignition

Fig 3: Schematic, Code 42: C(3)I Ignition