PCM Power And Ground Circuit Troubleshooting (L4) (2018-19)

Engine starting check
- 1. Start the engine.

Does the engine start and idle smoothly?

YES

Go to the troubleshooting for CAN gateway system DTC (s) - Refer to: Communication Systems DTC Troubleshooting Index (2018-19) .

NO

Go to step 2.

Fuse check

- 1. Check the following fuse.

Fuse	No. A21 (15 A)
Location	Under-hood fuse/relay box

Is the fuse OK?

YES

Go to step 6.

Go to step 3.

Shorted wire check (+B IGP line)

- 1. Remove the blown No. A21 (15 A) fuse from the under-hood fuse/relay box.

- 2. Disconnect the following connector.

Relay circuit board connector B (16P)

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

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board connector B (16P): disconnected
Test point 1	Relay circuit board connector B (16P) No. 4
Test point 2	Body ground

Is there continuity?

YES

Repair a short in the +B IGP wire between the No. A21 (15 A) fuse and the relay circuit board. If the wire is OK, replace the under-hood fuse/relay box . Also replace the No. A21 (15 A) fuse.

Go to step 4.

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.

- 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)
CMP sensor B 3P connector
CKP sensor 3P connector
Injector relay

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board connector B (16P): disconnected
Test point 1	Relay circuit board connector B (16P) No. 8, No. 9, and No. 10
Test point 2	Body ground

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 - Refer to: PCM Removal and Installation (With SH-AWD), or PCM Removal and Installation (Without SH-AWD) . Also replace the No. A21 (15 A) fuse in the under-hood fuse/relay box.

Parts are OK. Go to step 5.

Shorted wire check (FI MAIN RLY OUT line)

- 1. Disconnect the following parts or connectors:

PGM-FI main relay 2
PCM connector B (51P)
CMP sensor B 3P connector
CKP sensor 3P connector
Injector relay

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

Test condition	Vehicle OFF (LOCK) mode
Relay circuit board connector B (16P): disconnected
PGM-FI main relay 2: disconnected
PCM connector B (51P): disconnected
CMP sensor B 3P connector: disconnected
CKP sensor 3P connector: disconnected
Injector relay: disconnected
Test point 1	Relay circuit board connector B (16P) No. 8, No. 9, and No. 10
Test point 2	Body ground

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. A21 (15 A) fuse in the under-hood fuse/relay box.

The FI MAIN RLY OUT wire is OK. Replace the relay circuit board . Also replace the No. A21 (15 A) fuse in the under-hood fuse/relay box.

Fuse check 2

- 1. Check the following fuse.

Fuse	No. B9 (20 A)
Location	Under-dash fuse/relay box

Is the fuse OK?

YES

Go to step 11.

Go to step 7.

Relay check
- 1. Remove the blown No. B9 (20 A) fuse from the under-dash fuse/relay box.

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

Courtesy 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. B9 (20 A) fuse.

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 point 1	PGM-FI main relay 2 4P socket (female terminals) No. 2:
Test point 2	Body ground

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

Is there continuity?

YES

Go to step 9.

Go to step 10.

Shorted wire check (IG1 FUEL PUMP line)

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

- 2. Disconnect the following connector.

PCM connector A (51P)

- 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 point 1	PCM connector A (51P) No. 10 - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)
Test point 2	Body ground

Is there continuity?

YES

Repair a short in the IG1 FUEL PUMP wire between the PCM (A10) and the No. B9 (20 A) fuse in the under-dash fuse/relay box.

The IG1 FUEL PUMP wire is OK. Replace the No. B9 (20 A) fuse in the under-dash fuse/relay box, and check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM - Refer to: PCM Removal and Installation (With SH-AWD), or PCM Removal and Installation (Without SH-AWD) .

Shorted wire check (FUEL PUMP RLY OUT line)

- 1. Remove the access panel.

- 2. Disconnect the following connector.

Fuel tank unit 4P connector

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

Test condition	Vehicle OFF (LOCK) mode
	PGM-FI main relay 2: disconnected
	Fuel tank unit 4P connector: 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 FUEL PUMP RLY OUT wire between PGM-FI main relay 2 and the fuel tank unit. Also replace the No. B9 (20 A) fuse in the under-dash fuse/relay box.

The FUEL PUMP RLY OUT wire is OK. Check the fuel pump, and replace it - Refer to: Fuel Tank Unit Removal and Installation (With SH-AWD), or Fuel Tank Unit Removal and Installation (Without SH-AWD) if needed. Also replace the No. B9 (20 A) fuse in the under-dash fuse/relay box.

Open wire check (IG1 FUEL PUMP line)

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

- 2. Disconnect the following connector.

PCM connector A (51P)

- 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 point 1	PCM connector A (51P) No. 10 - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)
Test point 2	Body ground

Is there battery voltage?

YES

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

Repair an open in the IG1 FUEL PUMP wire between the PCM (A10) and the No. B9 (20 A) fuse in the under-dash fuse/relay box.

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 point 1	PCM connector A (51P) No. 8 - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)
Test point 2	Body ground

Is there battery voltage?

YES

Go to step 15.

Go to step 13.

Open wire check (+B IGP line)

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

- 2. Disconnect the following connector.

Relay circuit board connector B (16P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (51P): disconnected
	Relay circuit board connector B (16P): disconnected
Test point 1	Relay circuit board connector B (16P) No. 4
Test point 2	Body ground

Is there battery voltage?

YES

Go to step 14.

Repair an open in the +B IGP wire between the relay circuit board and the No. A21 (15 A) fuse in the under-dash fuse/relay box. If the wire is OK, replace the under-hood fuse/relay box . Also replace the No. A21 (15 A) fuse.

Open wire check (FI MAIN RLY CL- line)

- 1. Disconnect the following connector.

Relay circuit board connector A (10P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (51P): disconnected
	Relay circuit board connector B (16P): disconnected
	Relay circuit board connector A (10P): disconnected
Test point 1	Relay circuit board connector A (10P) No. 9
Test point 2	PCM connector A (51P) No. 8 - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)

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 - Refer to: PCM Removal and Installation (With SH-AWD), or PCM Removal and Installation (Without SH-AWD) .

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

Open wire check (+B IGP line)

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

- 2. Disconnect the following connector.

Relay circuit board connector B (16P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (51P): disconnected
	Relay circuit board connector B (16P): disconnected
Test point 1	Relay circuit board connector B (16P) No. 4
Test point 2	Body ground

Is there battery voltage?

YES

Go to step 16.

Replace the under-hood fuse/relay box .

Open wire check (IGP (ECU)/FI MAIN RLY OUT line)

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

- 2. Disconnect the following connector.

PCM connector B (51P)

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

Test condition	Vehicle OFF (LOCK) mode
	PCM connector A (51P): disconnected
	Relay circuit board connector B (16P): disconnected
	PCM connector B (51P): disconnected
Test point 1	Relay circuit board connector B (16P) No. 8
Test point 2	PCM connector B (51P) No. 9 - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)

Is there continuity?

YES

The IGP (ECU)/FI MAIN RLY OUT wire is OK. Go to step 17.

Repair an open in the IGP (ECU)/FI MAIN RLY OUT wire between the PCM (B9) and the relay circuit board.

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

Is the relay circuit board OK?

YES

Go to step 18.

NO

Replace the relay circuit board .

Open wire check (GND1, GND2, HT GND, 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	Vehicle OFF (LOCK) mode
	PCM connector A (51P): disconnected
	Relay circuit board connector B (16P): disconnected
	PCM connector B (51P): disconnected
	PCM connector C (51P): disconnected

Connector	Terminal
PCM connector B (51P) - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)	No. 16
	No. 20
PCM connector C (51P) - Refer to: PCM Connector for Inputs and Outputs (L4) (2018-19)	No. 9
	No. 17

Is there continuity?

YES

The GND1, GND2, HT GND, and PGM wires are OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM - Refer to: PCM Removal and Installation (With SH-AWD), or PCM Removal and Installation (Without SH-AWD) .

Repair an open in the GND1, GND2, HT GND, and/or PGM wire between the PCM (B16, B20, C9, C17) and G101.