Fuel Pump Circuit Troubleshooting

If you suspect a problem with the fuel pump, check that the fuel pump actually runs; when it is on, you will hear some noise if you listen to the fuel fill port with the fuel fill cap removed. The fuel pump should run for 2 seconds when the vehicle is turned to ON mode. If the fuel pump does not make noise, check as follows:

• 1. Under-dash fuse/relay box internal circuit check:

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

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

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  - 3. Turn the vehicle to the ON mode.

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

  Test condition	Vehicle ON mode
  	PGM-FI main relay 2: disconnected
  Test point 1	PGM-FI main relay 2 4P socket No. 3
  Test point 2	Body ground

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  Is there battery voltage?

  YES 

  Go to step 2.

  NO 

  • Replace PGM-FI main relay 1.
  • If needed, replace the under-dash fuse/relay box .
• 2. Open wire check (IG1 FUEL PUMP line):

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

  Test condition	Vehicle ON mode
  	PGM-FI main relay 2: disconnected
  Test point 1	PGM-FI main relay 2 4P socket No. 2
  Test point 2	Body ground

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  Is there battery voltage?

  YES 

  Go to step 3.

  NO 

  • Check the No. B4 (15 A) fuse in the under-dash fuse/relay box.
  • If needed, replace the under-dash fuse/relay box .
• 3. Open wire check (FUEL PUMP RLY CL- line):

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

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

  SCS Short

  - 3. Disconnect the following connector.

  PCM connector A (51P)

  - 4. 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	PGM-FI main relay 2 4P socket No. 4
  Test point 2	PCM connector A (51P) No. 14

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  Is there continuity?

  YES 

  The FUEL PUMP RLY CL- wire is OK. Go to step 4.

  NO 

  Repair an open in the FUEL PUMP RLY CL- wire between PGM-FI main relay 2 and the PCM (A14).

• 4. Determine possible failure area (PGM-FI main relay 2 or under-dash fuse/relay box, others):

  - 1. Reinstall PGM-FI main relay 2.

  - 2. Connect terminals A and B with a jumper wire.

  Terminal A	PCM connector A (51P) No. 3
  Terminal B	Body ground

  - 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
  	PCM connector A (51P) terminal No. 3: jumped to body ground
  Test point 1	PCM connector A (51P) No. 14
  Test point 2	Body ground

  Is there battery voltage?

  YES 

  Go to step 6.

  NO 

  Go to step 5.

• 5. PGM-FI main relay 2 check:

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

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

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  - 3. Test PGM-FI main relay 2 .

  Is the relay OK?

  YES 

  Replace the under-dash fuse/relay box .

  NO 

  Replace PGM-FI main relay 2.

• 6. PCM operation check:

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

  - 2. Reconnect PCM connector A (51P).

  - 3. Exit the SCS mode with the HDS.

  SCS Open

  - 4. Turn the vehicle to the ON mode, and measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode within 2 seconds
  Test point 1	Under-dash fuse/relay box connector C (38P) No. 35
  Test point 2	Body ground

  Is there battery voltage?

  YES 

  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 

  Go to step 7.

• 7. Determine possible failure area (FUEL PUMP RLY OUT line, GND line):

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

  - 2. Remove the access panel from the floor.

  - 3. Disconnect the following connector.

  Fuel tank unit 4P connector

  - 4. Turn the vehicle to the ON mode, and measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode within 2 seconds
  	Fuel tank unit 4P connector: disconnected
  Test point 1	Fuel tank unit 4P connector No. 1
  Test point 2	Body ground

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  Is there battery voltage?

  YES 

  Go to step 9.

  NO 

  Go to step 8.

• 8. Open wire check (FUEL PUMP RLY OUT line):

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

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

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  - 3. Connect terminals A and B with a jumper wire.

  Terminal A	PGM-FI main relay 2 4P socket No. 1
  Terminal B	PGM-FI main relay 2 4P socket No. 2

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

  Test condition	Vehicle ON mode
  	Fuel tank unit 4P connector: disconnected
  	PGM-FI main relay 2 : disconnected
  	PGM-FI main relay 2 4P socket No. 1 and No. 2: jumped
  Test point 1	Fuel tank unit 4P connector No. 1
  Test point 2	Body ground

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  Is there battery voltage?

  YES 

  The FUEL PUMP RLY OUT wire is OK. Replace PGM-FI main relay 2.

  NO 

  Repair an open in the FUEL PUMP RLY OUT wire between PGM-FI main relay 2 and the fuel tank unit.

• 9. Open wire check (GND line):

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

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

  Test condition	Vehicle OFF (LOCK) mode
  	Fuel tank unit 4P connector: disconnected
  Test point 1	Fuel tank unit 4P connector No. 3
  Test point 2	Body ground

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  Is there continuity?

  YES 

  The GND wire is OK. Replace the fuel pump .

  NO 

  Repair an open in the GND wire between the fuel tank unit and G603.