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 3.
     
NO
     
     
     
Go to step 2.
2.
Open wire check (FI MAIN RLY OUT line):

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.


?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


?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):

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 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):

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


?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. 14
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 (A14).?
5.
Determine possible failure area (PGM-FI main relay 2, others):

Determine possible failure area (PGM-FI main relay 2, others)
?1.
Remove the jumper wire.

?2.
Reinstall PGM-FI main relay 2.

?3.
Connect terminals A and B with a jumper wire.
Terminal A
PCM connector A (51P) No. 3
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. 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
     
     
     
Replace PGM-FI main relay 2.?
6.
PCM operation check:

PCM operation check
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Remove the jumper wire.

?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):

Determine possible failure area (FUEL PUMP RLY OUT line, GND line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Fuel tank unit 4P connector

?3.
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


Is there battery voltage?

     
YES
     
     
     
Go to step 10.
     
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.
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


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:

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 F (8P) No. 3
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):

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 4P connector and G403.?