Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSHONDA2020CIVIC SPORT, 4D HATCHBACK, STANDARD TRANSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE MECHANICALFUEL SYSTEMENGINE CONTROL / ENGINE MECHANICAL - TESTING & TROUBLESHOOTINGTROUBLESHOOTINGPCM POWER AND GROUND CIRCUIT TROUBLESHOOTING (L15BY) (2018 2019 2020)

2020 Honda Civic Sport, 4D Hatchback, Standard Trans

PCM Power and Ground Circuit Troubleshooting (L15BY) (2018 2019 2020)

2020 Honda Civic Sport, 4D Hatchback, Standard TransSECTION PCM Power and Ground Circuit Troubleshooting (L15BY) (2018 2019 2020)

Engine starting check
-1. Try to start the engine.

Does the engine start and idle smoothly?

YES (without multipurpose camera unit)

Go to the F-CAN circuit troubleshooting .

YES (with multipurpose camera unit)

Go to the troubleshooting for CAN gateway system DTC (s) .

NO

Go to step 2.
Fuse check 1
-1. Turn the vehicle to the OFF (LOCK) mode.

-2. Check the following fuse.

Fuse No. A12

Is the fuse OK?

YES

Go to step 3.

NO

Go to step 4.

Determine possible failure area (+B BACKUP FI-ECU line, others)

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

-2. Disconnect the following connector.

PCM connector A (50P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
Test point 1	PCM connector A (50P) No. 7
Test point 2	Body ground

Is there battery voltage?

YES

Go to step 5.

Repair an open in the +B BACKUP FI-ECU wire between PCM (A7) and the No. A12 fuse .

Shorted wire check (+B BACKUP FI-ECU line)

-1. Remove the blown No. A12 fuse .

-2. Jump the SCS line with the HDS, and wait more than 1 minute.

-3. Disconnect the following connector.

PCM connector A (50P)

-4. Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
Test point 1	PCM connector A (50P) No. 7
Test point 2	Body ground

Is there continuity?

YES

Repair a short in the +B BACKUP FI-ECU wire between the PCM (A7) and the No. A12 fuse. Also replace the No. A12 fuse.

Go to step 5.

Fuse check 2
-1. Check the following fuse.

Fuse No. A7

Is the fuse OK?

YES

Go to step 9.

NO

Go to step 6.

Shorted wire check (+B IGP line)

-1. Remove the blown No. A7 fuse .

-2. Disconnect the following connector.

Relay circuit board connector C (18P)

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

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board connector C (18P): disconnected
	PCM connector A (50P): disconnected

Test point 1	Relay circuit board connector C (18P) (female terminals) No. 18:
Test point 2	Body ground

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

Is there continuity?

YES

Repair a short in the +B IGP wire between the No. A7 fuse and the relay circuit board. If the wire is OK, replace the under-hood fuse/relay box . Also replace the No. A7 fuse.

Go to step 7.

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

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 A (50P)

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board connector C (18P): disconnected

Test point 1	Relay circuit board connector C (18P) (female terminals) No. 17:
Test point 2	Body ground

Courtesy 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, check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was substituted, replace the original PCM . Also replace the No. A7 fuse .

Parts are OK. Go to step 8.

Shorted wire check (FI MAIN RLY OUT line):

Disconnect the following parts or connectors:

PGM-FI main relay 2
PCM connector A (50P)

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

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board connector C (18P): disconnected
	PGM-FI main relay 2: disconnected

	PCM connector A (50P): disconnected
Test point 1	Relay circuit board connector C (18P) (female terminals) No. 17:
Test point 2	Body ground

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

Is there continuity?

YES

Repair a short in the FI MAIN RLY OUT wire between the relay circuit board and each part. Also replace the No. A7 fuse .

The FI MAIN RLY OUT wire is OK. Replace the relay circuit board . Also replace the No. A7 fuse .

Fuse check 3
-1. Check the following fuse.

Fuse No. B8

Is the fuse OK?

YES

Go to step 14.

NO

Go to step 10.
Relay check
-1. Remove PGM-FI main relay 2 .

-2. Test PGM-FI main relay 2 .

Is the relay OK?

YES

PGM-FI main relay 2 is OK. Go to step 11.

NO

Replace PGM-FI main relay 2. Also replace the No. B8 fuse .

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

-1. Remove the blown No. B8 fuse .

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

Test condition	Vehicle OFF (LOCK) mode
	PGM-FI main relay 2: disconnected
	PCM connector A (50P): disconnected
Test point 1	PGM-FI main relay 2 4P socket (female terminals) No. 1:
Test point 2	Body ground

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

Is there continuity?

YES

Go to step 12.

Go to step 13.

Shorted wire check (IG1 FUEL PUMP line)

-1. Disconnect the following connector.

Under-dash fuse/relay box connector C (27P)

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

Test condition	Vehicle OFF (LOCK) mode
	PGM-FI main relay 2: disconnected
	Under-dash fuse/relay box connector C (27P): disconnected
	PCM connector A (50P): disconnected
Test point 1	PGM-FI main relay 2 4P socket (female terminals) No. 1:
Test point 2	Body ground

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

Is there continuity?

YES

Repair a short in the IG1 FUEL PUMP wire between PGM-FI main relay 2 and the No. B8 fuse. Also replace the No. B8 fuse .

The IG1 FUEL PUMP wire is OK. Replace the No. B8 fuse . If the fuse blown again, replace the under-dash fuse/relay box .

Shorted wire check (FUEL PUMP RLY OUT line)

-1. Disconnect the following connector.

Fuel tank unit 4P connector

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

Test condition	Vehicle OFF (LOCK) mode
	PGM-FI main relay 2: disconnected
	PCM connector A (50P): disconnected
	Fuel tank unit 4P connector: disconnected
Test point 1	Fuel tank unit 4P connector (female terminals) No. 1:
Test point 2	Body ground

Courtesy 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. B8 fuse .

The FUEL PUMP RLY OUT wire is OK. Check the fuel pump, and replace it if needed. Also replace the No. B8 fuse .

Open wire check (IG1 FUEL PUMP line)

-1. Remove PGM-FI main relay 2 .

-2. Turn the vehicle to the ON mode.

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

Test condition	Vehicle ON mode
	PCM connector A (50P): disconnected
	PGM-FI main relay 2: disconnected
Test point 1	PGM-FI main relay 2 4P socket (female terminals) No. 1:
Test point 2	Body ground

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

Is there battery voltage?

YES

The IG1 FUEL PUMP wire is OK. Go to step 15.

Repair an open in the IG1 FUEL PUMP wire between the No. B8 fuse and PGM-FI main relay 2.

Fuse check 4
-1. Turn the vehicle to the OFF (LOCK) mode.

-2. Check the following fuse.

Fuse No. B11

Is the fuse OK?

YES

Go to step 17.

NO

Go to step 16.

Shorted wire check (IG1 (MONI)/IG1 MON line)

-1. Disconnect the following connector.

PCM connector E (80P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
Test point 1	PCM connector E (80P) No. 36
Test point 2	Body ground

Is there continuity?

YES

Repair a short in the IG1 (MONI)/IG1 MON wire between the PCM (E36) and the No. B11 fuse. Also replace the No. B11 fuse .

The IG1 (MONI)/IG1 MON wire is not shorted. Go to step 18.

Open wire check (IG1 (MONI)/IG1 MON line)

-1. Reinstall the No. B11 fuse .

-2. Disconnect the following connector.

PCM connector E (80P)

-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 (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
Test point 1	PCM connector E (80P) No. 36
Test point 2	Body ground

Is there battery voltage?

YES

The IG1 (MONI)/IG1 MON wire is OK. Go to step 18.

Repair an open in the IG1 (MONI)/IG1 MON wire between the PCM (E36) and the No. B11 fuse.

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

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

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
Test point 1	PCM connector A (50P) No. 5
Test point 2	Body ground

Is there battery voltage?

YES

Go to step 21.

Go to step 19.

Open wire check (+B IGP line)

-1. Disconnect the following connector.

Relay circuit board connector C (18P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
	Relay circuit board connector C (18P): disconnected
Test point 1	Relay circuit board connector C (18P) (female terminals) No. 18:
Test point 2	Body ground

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

Is there battery voltage?

YES

Go to step 20.

Repair an open in the +B IGP wire between the relay circuit board and the No. A7 fuse .

Open wire check (FI MAIN RLY CL- line)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
	Relay circuit board connector C (18P): disconnected
Test point 1	Relay circuit board connector C (18P) (female terminals) No. 5:
Test point 2	PCM connector A (50P) No. 5

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

Is there continuity?

YES

The FI MAIN RLY CL- wire is OK. Remove and test the relay circuit board . If the relay circuit board is OK, check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was substituted, replace the original PCM .

Repair an open in the FI MAIN RLY CL- wire between the PCM (A5) and the relay circuit board.

Open wire check (FI MAIN RLY OUT line)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
	Relay circuit board connector C (18P): disconnected
Test point 1	Relay circuit board connector C (18P) (female terminals) No. 17:

Test point 2

PCM connector A (50P) No. 8

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

Is there continuity?

YES

The FI MAIN RLY OUT wire is OK. Go to step 22.

Repair an open in the FI MAIN RLY OUT wire between the PCM (A8) and the relay circuit board.

Relay circuit board check
-1. Remove and test the relay circuit board .

Is the relay circuit board OK?

YES

The relay circuit board is OK. Go to step 23.

NO

Replace the relay circuit board .

Open wire check (GND lines)

-1. Check for continuity between the following test points and body ground individually.

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (50P): disconnected
	PCM connector E (80P): disconnected
	PGM-FI main relay 2: disconnected
	Relay circuit board: removed

Connector	Terminal
PCM connector A (50P)	No. 13
PCM connector E (80P)	No. 7
	No. 8
	No. 22
	No. 23
	No. 24

Is there continuity?

YES

The FI ECU GND, INJ GND1, INJ GND2, GND2, GND3, and GND4 wires are OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM , then recheck. If the symptom/indication goes away and the PCM was substituted, replace the original PCM .

Repair an open in the FI ECU GND, INJ GND1, or INJ GND2 wire between the PCM (A13, E7, E8) and G102, or an open in the GND2, GND3, or GND4 wire between the PCM (E22, E23, E24) and G101.

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When to See a Mechanic

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

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.