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DTC B12C5: Engine Start/Stop Switch Failure

WARNING: This page is about a different car, the 2010 Acura TL and 2009 Acura TL. However, it is still accessible from the selected car via links, so may be relevant.
  1. Clear the DTCs with the HDS.
  2. Press the engine start/stop button at least 20 times, then wait for at least 20 seconds.
  3. Check for DTCs with the HDS.

    Is DTC B12C5 indicated? 

    YES  -Go to step 4.

    NO  -Intermittent failure, the system is OK at this time. Check for loose or poor connections.

  4. Do the engine start/stop switch test (see ENGINE START/STOP SWITCH TEST/REPLACEMENT  ).

    Is the engine start/stop switch OK? 

    YES  -Go to step 5.

    NO  -Replace the engine start/stop switch (see ENGINE START/STOP SWITCH TEST/REPLACEMENT  ).

  5. Reconnect the engine start/stop switch 10P connector.
  6. Measure the voltage between body ground and engine start/stop switch 10P connector terminal No. 1.
    Fig 1: Measuring Voltage Between Body Ground And Engine Start/Stop Switch 10P Connector Terminal No. 1
    G06680302Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES  -Go to step 7.

    NO  -Check the No. 12 (10 A) fuse in the passenger's under-dash fuse/relay box. If the fuse is OK, check for an open in the RED wire.

  7. Press and hold the engine start/stop button.
  8. Measure the voltage between body ground and engine start/stop switch 10P connector terminal No. 4.
    Fig 2: Measuring Voltage Between Engine Start/Stop Switch 10P Connector Terminal No. 4 And Body Ground
    G06680303Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there less than 0.2 V? 

    YES  -Go to step 9.

    NO  -Repair an open or high resistance in the wire or poor ground (G405).

  9. Disconnect the engine start/stop switch 10P connector.
  10. Disconnect power control unit connector C (36P).
  11. Check for continuity between engine start/stop switch 10P connector terminals No. 2 and No. 5, and power control unit connector C (36P) terminals No. 8 and No. 7 respectively.
    Fig 3: Checking Continuity Between Engine Start/Stop Switch 10P Connector Terminals And Power Control Unit Connector C (36P) Terminals
    G06680304Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Replace the power control unit (see POWER CONTROL UNIT  ).

    NO  -Repair an open or high resistance in the wire.

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