DLC Circuit Troubleshooting

If the ECM does not communicate with a scan tool, the HDS, or I/M test equipment, do this troubleshooting procedure.

1. Measure voltage between DLC terminal No. 16 and body ground.
   Fig 1: Measuring Voltage Between DLC Terminal No. 16 And Body Ground

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   Is there battery voltage? 

   1. YES -  Go to step 2.
   2. NO -  Repair open in the wire between DLC terminal No. 8 and the ACGS (15 A) fuse in the under-hood fuse/relay box.
2. Measure voltage between DLC terminals No. 4 and No. 16.
   Fig 2: Measuring Voltage Between DLC Terminals No. 4 And No. 16

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   Is there battery voltage? 

   1. YES -  Go to step 3.
   2. NO -  Repair open in the wire between DLC terminal No. 8 and body ground (G401).
3. Measure voltage between DLC terminals No. 5 and No. 16.
   Fig 3: Measuring Voltage Between DLC Terminals No. 5 And No. 16

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   Is there battery voltage? 

   1. YES -  Go to step 4.
   2. NO -  Repair open in the wire between DLC terminal No. 8 and body ground (G101).
4. Turn the ignition switch ON (II).
5. Measure voltage between DLC terminals No. 5 and No. 7.
   Fig 4: Measuring Voltage Between DLC Terminals No. 5 And No. 7

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   Is there 8.5 V or more? 

   1. YES -  Go to step  10.
   2. NO -  Go to step 6.
6. Turn the ignition switch OFF.
7. Disconnect ECM connector A (32P). Make sure the scan tool or the HDS is disconnected from the DLC.
8. Check for continuity between DLC terminal No. 7 and body ground.
   Fig 5: Checking Continuity Between DLC Terminal No. 7 And Body Ground

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   Is there continuity? 

   1. YES -  Repair short to ground in the wire between DLC terminal No. 15 and the ECM (A21). After repairing the wire, check for DTCs with a scan tool or the HDS, and go to the indicated DTC's troubleshooting .
   2. NO -  Go to step 9.
9. Check for continuity between DLC terminal No. 15 and ECM terminal A21.
   Fig 6: Checking Continuity Between DLC Terminal No. 15 And ECM Terminal A21

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   Is there continuity? 

   1. YES -  Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If the symptom/indication goes away, replace the original ECM (see ECM REPLACEMENT  ).
   2. NO -  Repair open in the wire between DLC terminal No. 7 and the ECM (A21). After repairing the wire, check for DTCs with a scan tool or the HDS, and go to the indicated DTC's troubleshooting.
10. Turn the ignition switch OFF.
11. Disconnect ECM connector A (32P). Make sure a scan tool or the HDS is disconnected from the DLC.
12. Turn the ignition switch ON (II).
13. Measure voltage between DLC terminals No. 5 and No. 7.
    Fig 7: Measuring Voltage Between DLC Terminals No. 5 And No. 7

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there 0 V? 

    1. YES -  Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If the symptom/indication goes away, replace the original ECM (see ECM REPLACEMENT  ).
    2. NO -  Repair short to power in the wire between the DLC terminal No. 7 and the ECM (A21). After repairing the wire, check for DTCs with a scan tool or the HDS, and go to the indicated DTC's troubleshooting.