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Diagnostic Circuit Check: Notes

NOTE: DIAGNOSTIC CIRCUIT CHECK must be performed before any other testing. This test will determine if diagnostic system is working properly.
  1. With ignition on and engine stopped, note "Check Engine" light. If light is off, go to TEST 5. If light is on, go to step 2). If light flashes, check for grounded wire to ECM connector terminal C45-1. If wire is not grounded, ECM is faulty.
  2. Ground ALDL terminal No. 1 (White wire) and note "Check Engine" light. See Fig 1 . If light does not flash, go to TEST 6. If light flashes code 12, note any additional codes.
    Fig 1: ALDL & ECM Connectors & Location
    G94681Courtesy of ISUZU MOTOR CO.
  3. If code 52 or 55 flashes, replace ECM. If no additional codes flash, turn ignition off, clear codes and remove ground from ALDL terminal No. 1.
  4. Set parking brake and run engine for 2 minutes. Note "Check Engine" light. If light is off, go to step 6). If light is on, ground ALDL terminal No. 1.
  5. If code flashes, go to appropriate code information. If light flashes, but no code is noted, replace ECM.
  6. Refer to additional codes in step 2). If no additional codes, verify customers complaint. If additional codes are 13, 15, 21, 22, 31, 44 or 45, go to appropriate code information. For all others, trouble is intermittent. Make physical check of circuits indicated by code.
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