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PCM Power and Ground Circuit Troubleshooting (2016-18)

  1. Engine starting check:

    Try to start the engine.

    Does the engine start and idle smoothly?

    YES 

    Go to the F-CAN circuit troubleshooting .?

    NO 

    Go to step 2.

  2. Fuse check:

    Check the following fuse.

    Fuse No. A25 (15 A)
    Location Under-hood fuse/relay box

    Is the fuse OK?

    YES 

    Go to step 7.

    NO 

    Go to step 3.

  3. Determine possible failure area (+B IGP line, others):

    - 1. Remove the blown No. A25 (15 A) fuse from the under-hood fuse/relay box.

    - 2. Remove PGM-FI main relay 1 (A) from the under-dash fuse/relay box.

    GHH72805Courtesy of HONDA, U.S.A., INC.

    - 3. Check for continuity between test points 1 and 2.

    Test condition OFF mode
      PGM-FI main relay 1: disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 1 and No. 3
    Test point 2 Body ground
    GHH72806Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Go to step 4.

    NO 

    Go to step 5.

  4. Shorted wire check (+B IGP line):

    - 1. Disconnect the following connector.

    Under-dash fuse/relay box connector D (32P)

    - 2. Check for continuity between test points 1 and 2.

    Test condition OFF mode
    Under-dash fuse/relay box connector D (32P): disconnected
    PGM-FI main relay 1: disconnected
    Test point 1 Under-dash fuse/relay box connector D (32P) No. 9
    Test point 2 Body ground
    GHH72807Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the +B IGP wire between the No. A25 (15 A) fuse and the under-dash fuse/relay box. If needed, replace the under-hood fuse/relay box . Also replace the No. A25 (15 A) fuse.?

    NO 

    Replace the under-dash fuse/relay box . Also replace the No. A25 (15 A) fuse in the under-hood fuse/relay box.?

  5. Part(s) internal circuit check (short in FI MAIN RLY OUT line):

    - 1. Jump the SCS line with the HDS, and wait more than 1 minute.

    SCS Short

    - 2. Disconnect each of the parts or connectors below, one at a time, then check for continuity between test points 1 and 2.

    • PGM-FI main relay 2
    • PCM connector B (51P)
    • Each injector 2P connector
    • CMP sensor 3P connector
    • CKP sensor 3P connector
    • Electronic throttle control system (ETCS) control relay
    Test condition OFF mode
      PGM-FI main relay 1: disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 2
    Test point 2 Body ground
    GHH72808Courtesy of HONDA, U.S.A., INC.

    Does continuity go away when one of the above components is disconnected?

    YES 

    Replace the part that made the short to body ground go away when it was disconnected. If the part is the PCM, update the PCM  if it does not have the latest software, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM . Also replace the No. A25 (15 A) fuse in the under-hood fuse/relay box.?

    NO 

    Parts are OK. Go to step 6.

  6. Shorted wire check (FI MAIN RLY OUT line):

    - 1. Disconnect the following parts or connectors:

    • PGM-FI main relay 2
    • PCM connector B (51P)
    • Each injector 2P connector
    • CMP sensor 3P connector
    • CKP sensor 3P connector
    • Electronic throttle control system (ETCS) control relay

    - 2. Check for continuity between test points 1 and 2.

    Test condition OFF mode
    PGM-FI main relay 1: disconnected
    PGM-FI main relay 2: disconnected
    PCM connector B (51P): disconnected
    Each injector 2P connector: disconnected
    CMP sensor 3P connector: disconnected
    CKP sensor 3P connector: disconnected
    ETCS control relay: disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 2
    Test point 2 Body ground
    GHH72809Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the FI MAIN RLY OUT wire between PGM-FI main relay 1 and each part. Also replace the No. A25 (15 A) fuse in the under-hood fuse/relay box.?

    NO 

    The FI MAIN RLY OUT wire is OK. Replace PGM-FI main relay 1. Also replace the No. A25 (15 A) fuse in the under-hood fuse/relay box.?

  7. Fuse check 2:

    Check the following fuse.

    Fuse No. B4 (15 A)
    Location Under-dash fuse/relay box

    Is the fuse OK?

    YES 

    Go to step 12.

    NO 

    Go to step 8.

  8. Relay check:

    - 1. Remove the blown No. B4 (15 A) fuse from the under-dash fuse/relay box.

    - 2. Remove PGM-FI main relay 2 (A) from the under-dash fuse/relay box.

    GHH72810Courtesy of HONDA, U.S.A., INC.

    - 3. Test PGM-FI main relay 2 .

    Is the relay OK?

    YES 

    PGM-FI main relay 2 is OK. Go to step 9.

    NO 

    Replace PGM-FI main relay 2. Also replace the No. B4 (15 A) fuse.?

  9. Determine possible failure area (IG1 FUEL PUMP line, others):

    Check for continuity between test points 1 and 2.

    Test condition OFF mode
      PGM-FI main relay 2: disconnected
    Test point 1 PGM-FI main relay 2 4P socket No. 1
    Test point 2 Body ground
    GHH72811Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Go to step 10.

    NO 

    Go to step 11.

  10. Shorted wire check (IG1 FUEL PUMP line):

    - 1. Jump the SCS line with the HDS, and wait more than 1 minute.

    SCS Short

    - 2. Disconnect the following connector.

    PCM connector A (51P)

    - 3. Check for continuity between test points 1 and 2.

    Test condition OFF mode
      PGM-FI main relay 2: disconnected
      PCM connector A (51P): disconnected
    Test point 1 PCM connector A (51P) No. 18 
    Test point 2 Body ground

    Is there continuity?

    YES 

    Repair a short in the IG1 FUEL PUMP wire between the PCM (A18) and the No. B4 (15 A) fuse in the under-dash fuse/relay box.?

    NO 

    The IG1 FUEL PUMP wire is OK. Replace the No. B4 (15 A) fuse in the under-dash fuse/relay box, and update the PCM  if it does not have the latest software, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM .?

  11. Shorted wire check (FUEL PUMP RLY OUT line):

    - 1. Remove the access panel from the floor .

    - 2. Disconnect the following connector.

    Fuel tank unit 4P connector

    - 3. Check for continuity between test points 1 and 2.

    Test condition OFF mode
      PGM-FI main relay 2: disconnected
      Fuel tank unit 4P connector: disconnected
    Test point 1 Fuel tank unit 4P connector No. 1
    Test point 2 Body ground
    GHH72812Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the FUEL PUMP RLY OUT wire between PGM-FI main relay 2 and the fuel tank unit. Also replace the No. B4 (15 A) fuse in the under-dash fuse/relay box.?

    NO 

    The FUEL PUMP RLY OUT wire is OK. Check the fuel pump, and replace it if needed. Also replace the No. B4 (15 A) fuse in the under-dash fuse/relay box.?

  12. Open wire check (IG1 FUEL PUMP line):

    - 1. Jump the SCS line with the HDS, and wait more than 1 minute.

    SCS Short

    - 2. Disconnect the following connector.

    PCM connector A (51P)

    - 3. Press the engine start/stop button to select the ON mode.

    - 4. Measure the voltage between test points 1 and 2.

    Test condition ON mode
      PCM connector A (51P): disconnected
    Test point 1 PCM connector A (51P) No. 18 
    Test point 2 Body ground

    Is there battery voltage?

    YES 

    The IG1 FUEL PUMP wire is OK. Go to step 13.

    NO 

    Repair an open in the IG1 FUEL PUMP wire between the PCM (A18) and the No. B4 (15 A) fuse in the under-dash fuse/relay box.?

  13. Determine possible failure area (PGM-FI main relay 1 control circuit, others):

    - 1. Press the engine start/stop button to select the OFF mode.

    - 2. Measure the voltage between test points 1 and 2.

    Test condition OFF mode
      PCM connector A (51P): disconnected
    Test point 1 PCM connector A (51P) No. 7 
    Test point 2 Body ground

    Is there battery voltage?

    YES 

    Go to step 17.

    NO 

    Go to step 14.

  14. Determine possible failure area (+B IGP line, others):

    - 1. Remove PGM-FI main relay 1 (A) from the under-dash fuse/relay box.

    GHH72813Courtesy of HONDA, U.S.A., INC.

    - 2. Measure the voltage between test points 1 and 2.

    Test condition OFF mode
      PCM connector A (51P): disconnected
      PGM-FI main relay 1: disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 1 and No. 3
    Test point 2 Body ground
    GHH72814Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    Go to step 16.

    NO 

    Go to step 15.

  15. Open wire check (+B IGP line):

    - 1. Disconnect the following connector.

    Under-dash fuse/relay box connector D (32P)

    - 2. Measure the voltage between test points 1 and 2.

    Test condition OFF mode
      PCM connector A (51P): disconnected
      Under-dash fuse/relay box connector D (32P): disconnected
    Test point 1 Under-dash fuse/relay box connector D (32P) No. 9
    Test point 2 Body ground
    GHH72815Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    The +B IGP wire is OK. Replace the under-dash fuse/relay box . Also replace the No. A25 (15 A) fuse in the under-hood fuse/relay box.?

    NO 

    Repair an open in the +B IGP wire between the No. A25 (15 A) fuse and the under-dash fuse/relay box. If needed, replace the under-hood fuse/relay box . Also replace the No. A25 (15 A) fuse.?

  16. Open wire check (FI MAIN RLY CL- line):

    Check for continuity between test points 1 and 2.

    Test condition OFF mode
      PCM connector A (51P): disconnected
      PGM-FI main relay 1: disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 4
    Test point 2 PCM connector A (51P) No. 7 
    GHH72816Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The FI MAIN RLY CL- wire is OK. Test PGM-FI main relay 1 . If the relay is OK, update the PCM  if it does not have the latest software, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM .?

    NO 

    Repair an open in the FI MAIN RLY CL- wire between the PCM (A7) and PGM-FI main relay 1.?

  17. Determine possible failure area (+B IGP line, others):

    -1. Remove PGM-FI main relay 1 (A) from the under-dash fuse/relay box.

    GHH72817Courtesy of HONDA, U.S.A., INC.

    - 2. Measure the voltage between test points 1 and 2.

    Test condition OFF mode
    PCM connector A (51P): disconnected
    PGM-FI main relay 1: disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 1
    Test point 2 Body ground
    GHH72818Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    Go to step 19.

    NO 

    Go to step 18.

  18. Open wire check (+B IGP line):

    -1. Disconnect the following connector.

    Under-dash fuse/relay box connector D (32P)

    - 2. Measure the voltage between test points 1 and 2.

    Test condition OFF mode
    PCM connector A (51P): disconnected
    PGM-FI main relay 1: disconnected
    Under-dash fuse/relay box connector D (32P): disconnected
    Test point 1 Under-dash fuse/relay box connector D (32P) No. 9
    Test point 2 Body ground
    GHH72819Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    Go to step 19.

    NO 

    Repair an open in the +B IGP wire between the under-dash fuse/relay box and No. A25 (15 A) fuse in the under-hood fuse/relay box.?

  19. 19.Open wire check (IGP/FI MAIN RLY OUT line):

    -1. Disconnect the following connector.

    PCM connector B (51P)

    - 2. Check for continuity between test points 1 and 2.

    Test condition OFF mode
    PCM connector A (51P): disconnected
    PGM-FI main relay 1: disconnected
    PCM connector B (51P): disconnected
    Test point 1 PGM-FI main relay 1 4P socket No. 2
    Test point 2 PCM connector B (51P) No. 10 
    GHH72820Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The IGP/FI MAIN RLY OUT wire is OK. Go to step 20.

    NO 

    Repair an open in the IGP/FI MAIN RLY OUT wire between the PCM (B10) and PGM-FI main relay 1.?

  20. Relay check:

    Test PGM-FI main relay 1 .

    Is the relay OK?

    YES 

    The relay is OK. Go to step 21.

    NO 

    Replace PGM-FI main relay 1.?

  21. Open wire check (GND1, GND2, GND3, PGM lines):

    -1. Disconnect the following connector.

    PCM connector C (51P)

    - 2. Check for continuity between the following test points and body ground individually.

    Test condition OFF mode
      PCM connector A (51P): disconnected
      PCM connector B (51P): disconnected
      PCM connector C (51P): disconnected
      PGM-FI main relay 1: disconnected
    Connector Terminal
    PCM connector B (51P)  No. 11
    No. 20
    PCM connector C (51P)  No. 1
    No. 20

    Is there continuity?

    YES 

    The GND1, GND2, GND3, and PGM wires are OK. Update the PCM  if it does not have the latest software, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM .?

    NO 

    Repair an open in the GND1, GND2, GND3, and/or PGM wires between the PCM (B11, B20, C1, C20) and G101.?

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