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HOMESERVICE MANUALSACURA2018MDX BASEREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE MECHANICALMECHANICALENGINE CONTROL AND ENGINE MECHANICAL - SERVICE, TESTING AND TROUBLESHOOTING (EXCEPT HYBRID)TROUBLESHOOTINGPCM POWER AND GROUND CIRCUIT TROUBLESHOOTING (2014 2015)
2018 Acura MDX Base

PCM Power and Ground Circuit Troubleshooting (2014 2015)

2018 Acura MDX BaseSECTION PCM Power and Ground Circuit Troubleshooting (2014 2015)

PCM Power and Ground Circuit Troubleshooting 

  1. Engine starting check

    -1. Try to start the engine.

    Does the engine start and idle smoothly?

    YES 

    Go to the F-CAN circuit troubleshooting - Refer to: F-CAN Circuit Troubleshooting (2014 2015), or F-CAN Circuit Troubleshooting (2017 2018), or F-CAN Circuit Troubleshooting(Without CAN Gateway) (2016) .

    NO 

    Go to step 2.

  2. Fuse check

    -1. Check the following fuse.

    Fuse No. C10 (15 A)
    Location Under-hood fuse/relay box

    Is the fuse OK?

    YES 

    Go to step 6.

    NO 

    Go to step 3.

  3. Shorted wire check

    -1. Remove the blown No. C10 (15 A) fuse from the under-hood fuse/relay box.

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

    GHH320158Courtesy of HONDA, U.S.A., INC.

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

    Test condition Vehicle OFF (LOCK) mode
      PGM-FI main relay 1: disconnected
    Test circuit +B IGP
    Test point 1 PGM-FI main relay 1 4P socket No. 1
    Test point 2 Body ground
    Test circuit +B IGP
    Test point 1 PGM-FI main relay 1 4P socket No. 3
    Test point 2 Body ground
    GHH320159Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the +B IGP wire between the No. C10 (15 A) fuse and PGM-FI main relay 1. If the wire is OK, replace the under-hood fuse/relay box . Also replace the No. C10 (15 A) fuse.

    NO 

    Go to step 4.

  4. Part(s) internal circuit check (short in IGP line)

    -1. 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)
    • CMP sensor 3P connector
    • CKP sensor 3P connector
    • Injector relay
    • Electronic throttle control system (ETCS) control relay
    Test condition Vehicle OFF (LOCK) mode
    Test circuit IGP
    Test point 1 PGM-FI main relay 1 4P socket No. 2
    Test point 2 Body ground
    GHH320160Courtesy 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 - Refer to: PCM Removal and Installation (2014 2015), or PCM Removal and Installation (2016) , 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 - Refer to: PCM Removal and Installation (2016), or PCM Removal and Installation (2014 2015) . Also replace the No. C10 (15 A) fuse in the under-hood fuse/relay box.

    NO 

    Parts are OK. Go to step 5.

  5. Shorted wire check (IGP line)

    -1. Jump the SCS line with the HDS.

    - 2. Disconnect the following parts or connectors:

    • PGM-FI main relay 2
    • PCM connector B (51P)
    • MAF sensor/IAT sensor
    • CMP sensor
    • CKP sensor
    • Injector relay
    • Electronic throttle control system (ETCS) control relay
    • Radiator fan relay

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

    Test condition Vehicle OFF (LOCK) mode
      PGM-FI main relay 1: disconnected
      PGM-FI main relay 2: disconnected
      PCM connector B (51P): disconnected
      MAF sensor/IAT sensor 5P connector: disconnected
      CMP sensor 3P connector: disconnected
      CKP sensor 3P connector: disconnected
      Injector relay: disconnected
      Electronic throttle control system (ETCS) control relay: disconnected
      Radiator fan relay: disconnected
    Test circuit IGP
    Test point 1 PGM-FI main relay 1 4P socket No. 2
    Test point 2 Body ground
    GHH320161Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the IGP wire between PGM-FI main relay 1 and each part. Also replace the No. C10 (15 A) fuse in the under-hood fuse/relay box.

    NO 

    The IGP wire is OK. Replace PGM-FI main relay 1. Also replace the No. C10 (15 A) fuse in the under-hood fuse/relay box.

  6. Fuse check 2

    -1. Check the following fuse.

    Fuse No. D21 (20 A)
    Location Driver's under-dash fuse/relay box

    Is the fuse OK?

    YES 

    Go to step 11.

    NO 

    Go to step 7.

  7. Relay check

    -1. Remove the blown No. D21 (20 A) fuse from the driver's under-dash fuse/relay box.

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

    GHH320162Courtesy 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 8.

    NO 

    Replace PGM-FI main relay 2. Also replace the No. D21 (20 A) fuse in the driver's under-dash fuse/relay box.

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

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

    Test condition Vehicle OFF (LOCK) mode
      PGM-FI main relay 2: disconnected
    Test circuit IG1 FUEL PUMP
    Test point 1 PGM-FI main relay 2 4P socket No. 1
    Test point 2 Body ground
    GHH320163Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Go to step 9.

    NO 

    Go to step 10.

  9. Shorted wire check (IG1 FUEL PUMP line)

    -1. Jump the SCS line with the HDS.

    - 2. Disconnect the following connector.

    PCM connector A (51P) - Refer to: How to Troubleshoot the A/T System (2014 2015), or How to Troubleshoot the Fuel and Emissions Systems, or How to Troubleshoot the Brake Booster Pressure Monitoring System (2016 2017 2018 2019 2020), or How to Troubleshoot the Fuel and Emissions Systems(With Auto Idle Stop System) (2016)

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

    Test condition Vehicle OFF (LOCK) mode
      PGM-FI main relay 2: disconnected
      PCM connector A (51P): disconnected
    Test circuit IG1 FUEL PUMP
    Test point 1 PCM connector A (51P) No. 18 (YEL)
    Test point 2 Body ground
    GHH320164Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the IG1 FUEL PUMP wire between the No. D21 (20 A) fuse in the driver's under-dash fuse/relay box and the PCM (A18).

    NO 

    The IG1 FUEL PUMP wire is OK. Replace the No. D21 (20 A) fuse in the driver's under-dash fuse/relay box, and update the PCM  if it does not have the latest software, or substitute a known-good PCM - Refer to: PCM Removal and Installation (2014 2015), or PCM Removal and Installation (2016) , 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 - Refer to: PCM Removal and Installation (2016), or PCM Removal and Installation (2014 2015) .

  10. Shorted wire check (IGP line)

    -1. Disconnect the following connector.

    Fuel pump control module 6P connector

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

    Test condition Vehicle OFF (LOCK) mode
      PGM-FI main relay 2: disconnected
      Fuel pump control module 6P connector: disconnected
    Test circuit IGP
    Test point 1 PGM-FI main relay 2 4P socket No. 2
    Test point 2 Body ground
    GHH320165Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    Repair a short in the IGP wire between PGM-FI main relay 2 and the fuel pump control module 6P connector. Also replace the No. D21 (20 A) fuse in the driver's under-dash fuse/relay box.

    NO 

    The IGP wire is OK. Replace the No. D21 (20 A) fuse in the driver's under-dash fuse/relay box.

  11. Open wire check (IG1 FUEL PUMP line)

    -1. Jump the SCS line with the HDS.

    - 2. Disconnect the following connector.

    PCM connector A (51P) - Refer to: How to Troubleshoot the A/T System (2014 2015), or How to Troubleshoot the Fuel and Emissions Systems, or How to Troubleshoot the Brake Booster Pressure Monitoring System (2016 2017 2018 2019 2020), or How to Troubleshoot the Fuel and Emissions Systems(With Auto Idle Stop System) (2016)

    - 3. Turn the vehicle to the ON mode.

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

    Test condition Vehicle ON mode
      PCM connector A (51P): disconnected
    Test circuit IG1 FUEL PUMP
    Test point 1 PCM connector A (51P) No. 18 (YEL)
    Test point 2 Body ground
    GHH320166Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    The IG1 FUEL PUMP wire is OK. Go to step 12.

    NO 

    Repair an open in the IG1 FUEL PUMP wire between the No. D21 (20 A) fuse in the driver's under-dash fuse/relay box and the PCM (A18).

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

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

    Test condition Vehicle ON mode
      PCM connector A (51P): disconnected
    Test circuit MRLY
    Test point 1 PCM connector A (51P) No. 7 (RED)
    Test point 2 Body ground
    GHH320167Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    Go to step 15.

    NO 

    Go to step 13.

  13. Open wire check (+B IGP line)

    -1. Turn the vehicle to the OFF (LOCK) mode.

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

    GHH320168Courtesy of HONDA, U.S.A., INC.

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

    Test condition Vehicle OFF (LOCK) mode
      PCM connector A (51P): disconnected
      PGM-FI main relay 1: disconnected
    Test circuit +B IGP
    Test point 1 PGM-FI main relay 1 4P socket No. 3
    Test point 2 Body ground
    GHH320169Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    Go to step 14.

    NO 

    Repair an open in the +B IGP wire between PGM-FI main relay 1 and the No. C10 (15 A) fuse in the driver's under-dash fuse/relay box. If the wire is OK, replace the under-hood fuse/relay box . Also replace the No. C10 (15 A) fuse.

  14. Open wire check (MRLY line)

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

    Test condition Vehicle OFF (LOCK) mode
      PCM connector A (51P): disconnected
      PGM-FI main relay 1: disconnected
    Test circuit MRLY
    Test point 1 PGM-FI main relay 1 4P socket No. 4
    Test point 2 PCM connector A (51P) No. 7 (RED)
    GHH320170Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The MRLY wire is OK. Test PGM-FI main relay 1 - Refer to: Power Relay Test (2016), or Power Relay Test (2014 2015) . If the relay is OK, update the PCM  if it does not have the latest software, or substitute a known-good PCM - Refer to: PCM Removal and Installation (2016), or PCM Removal and Installation (2014 2015) , 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 - Refer to: PCM Removal and Installation (2014 2015), or PCM Removal and Installation (2016) .

    NO 

    Repair an open in the MRLY wire between the PCM (A7) and PGM-FI main relay 1.

  15. Open wire check (+B IGP line)

    -1. Turn the vehicle to the OFF (LOCK) mode.

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

    GHH320171Courtesy of HONDA, U.S.A., INC.

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

    Test condition Vehicle OFF (LOCK) mode
      PCM connector A (51P): disconnected
      PGM-FI main relay 1: disconnected
    Test circuit +B IGP
    Test point 1 PGM-FI main relay 1 4P socket No. 1
    Test point 2 Body ground
    GHH320172Courtesy of HONDA, U.S.A., INC.

    Is there battery voltage?

    YES 

    Go to step 16.

    NO 

    Replace the under-hood fuse/relay box .

  16. Open wire check (IGP line)

    -1. Jump the SCS line with the HDS.

    - 2. Disconnect the following connector.

    PCM connector B (51P) - Refer to: How to Troubleshoot the Fuel and Emissions Systems, or How to Troubleshoot the A/T System (2014 2015), or How to Troubleshoot the Brake Booster Pressure Monitoring System (2016 2017 2018 2019 2020), or How to Troubleshoot the Fuel and Emissions Systems(With Auto Idle Stop System) (2016)

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

    Test condition Vehicle OFF (LOCK) mode
      PCM connector A (51P): disconnected
      PCM connector B (51P): disconnected
      PGM-FI main relay 1: disconnected
    Test circuit IGP
    Test point 1 PGM-FI main relay 1 4P socket terminal No. 2
    Test point 2 PCM connector B (51P) No. 10 (YEL)
    GHH320173Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The IGP wire is OK. Go to step 17.

    NO 

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

  17. Relay check

    -1. Test PGM-FI main relay 1.

    Is PGM-FI main relay 1 OK?

    YES 

    PGM-FI main relay 1 is OK. Go to step 18.

    NO 

    Replace PGM-FI main relay 1.

  18. Open wire check (GND1 PG, GND2 LG, GND3 PG, PGM lines)

    -1. Disconnect the following connector.

    PCM connector C (51P) - Refer to: How to Troubleshoot the Fuel and Emissions Systems, or How to Troubleshoot the A/T System (2014 2015), or How to Troubleshoot the Brake Booster Pressure Monitoring System (2016 2017 2018 2019 2020), or How to Troubleshoot the Fuel and Emissions Systems(With Auto Idle Stop System) (2016)

    - 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 Test circuit Terminal
    PCM connector B (51P) GND1/PG No. 11 (BLK)
    GND2 LG No. 20 (BRN)
    PCM connector C (51P) PGM No. 1 (BLK)
    GND3/PG No. 20 (BLK)
    GHH320174Courtesy of HONDA, U.S.A., INC.
    GHH320175Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The GND1/PG, GND2 LG, GND3/PG, and PGM wires are OK. Update the PCM  if it does not have the latest software, or substitute a known-good PCM - Refer to: PCM Removal and Installation (2014 2015), or PCM Removal and Installation (2016) , 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 - Refer to: PCM Removal and Installation (2014 2015), or PCM Removal and Installation (2016) .

    NO 

    Repair an open in the wire between the PCM (B11, B20, C1, C20) and G101.

RENDER: 1.0x

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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  • • The engine overheats, stalls repeatedly, or misfires under load.
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