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:

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.


?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


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):

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


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):

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.


?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


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):

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:

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.


?3.
Test PGM-FI main relay 2.

Is the relay OK?

     
YES
     
     
     
     
NO
     
     
     
Replace PGM-FI main relay 2.?
6.
PCM operation check:

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.


?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):

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


Is there battery voltage?

     
YES
     
     
     
Go to step 9.
     
NO
     
     
     
Go to step 8.
8.
Open wire check (FUEL PUMP RLY OUT line):

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.


?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


?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


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):

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


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.?