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Code 42, Est Circuit Open Or Grounded: Notes

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Checks to see if ECM recognizes a fault. If a Code 42 is not set at this point, an intermittent problem exists and could be the result of a loose connection.
  2. With ECM disconnected, ohmmeter should indicate less than 500 ohms, which is normal resistance for the ignition module. A higher resistance indicates a fault in circuit No. 423, poor ignition module connection or faulty ignition module.
  3. If test light was illuminated when connected from 12 volts to ECM harness terminal "BC7", either circuit No. 423 is shorted to ground or ignition module is faulty.
  4. Checks to see if ignition module switches when bypass circuit is energized by 12 volts through test light. If ignition module switches, ohmmeter reading should shift to greater than 8000 ohms.
  5. Disconnecting ignition module should cause ohmmeter to indicate as if it were monitoring an open circuit (infinite reading). If ohmmeter has a reading other than infinity, circuit No. 423 is shorted to ground.
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