Fuel Pump Circuit Troubleshooting

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 3.

   NO 

   Go to step 2.

2. Open wire check (FI MAIN RLY OUT 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.

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   -3. Disconnect the following connector.

   Under-dash fuse/relay box connector Q (40P)

   -4. Connect terminals A and B with a jumper wire.

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

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   -5. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	PGM-FI main relay 1: disconnected
   	Under-dash fuse/relay box connector Q (40P): disconnected
   	PGM-FI main relay 1 4P socket No. 2: jumped to body ground
   Test point 1	Under-dash fuse/relay box connector Q (40P) No. 8
   Test point 2	Body ground

   Is there continuity?

   YES 

   Replace the under-dash fuse/relay box .

   NO 

   Repair an open in the FI MAIN RLY OUT wire between PGM-FI main relay 1 and the under-dash fuse/relay box.

3. 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 4.

   NO 

   • Check the No. C32 (15 A) fuse in the under-dash fuse/relay box.
   • If needed, replace the under-dash fuse/relay box .
4. 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.

   -3. Disconnect the following connector.

   PCM connector A (51P)

   -4. Connect terminals A and B with a jumper wire.

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

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   -5. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	PGM-FI main relay 2: disconnected
   	PGM-FI main relay 2 4P socket No. 4: jumped to body ground
   	PCM connector A (51P): disconnected
   Test point 1	PCM connector A (51P) No. 42
   Test point 2	Body ground

   Is there continuity?

   YES 

   The FUEL PUMP RLY CL- wire is OK. Go to step 5.

   NO 

   Repair an open in the FUEL PUMP RLY CL- wire between PGM-FI main relay 2 and the PCM (A42).

5. Determine possible failure area (PGM-FI main relay 2, others)

   -1. Remove the jumper wire from the PGM-FI main relay 4P socket.

   -2. Reinstall PGM-FI main relay 2.

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

   Terminal A	PCM connector A (51P) No. 7
   Terminal B	Body ground

   -4. Turn the vehicle to the ON mode.

   -5. 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. 9: jumped to body ground
   Test point 1	PCM connector A (51P) No. 42
   Test point 2	Body ground

   Is there battery voltage?

   YES 

   Go to step 6.

   NO 

   Replace PGM-FI main relay 2.

6. PCM operation check

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

   -2. Remove the jumper wire from PCM connector A (51P).

   -3. Reconnect PCM connector A (51P).

   -4. Exit the SCS mode with the HDS.

   -5. Turn the vehicle to the ON mode, and measure the voltage between test points 1 and 2.

   Test condition	Within 2 seconds after vehicle ON mode
   Test point 1	Under-dash fuse/relay box connector Q (40P) No. 32
   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. Reinstall PGM-FI main relay 2.

   -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	Within 2 seconds after vehicle ON mode
   	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 10.

   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. Turn the vehicle to the ON mode.

   -5. 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 

   Go to step 9.

9. Open wire check (FUEL PUMP RLY OUT line) 2

   -1. 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	Under-dash fuse/relay box connector N (52P) No. 19
   Test point 2	Body ground

   Is there battery voltage?

   YES 

   Repair an open in the FUEL PUMP RLY OUT wire between the under-dash fuse/relay box and the fuel tank unit.

   NO 

   The FUEL PUMP RLY OUT wire is OK. Replace the under-dash fuse/relay box.

10. 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 4P connector and G502.