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Subfuel Pump Circuit Troubleshooting

If you suspect a problem with the subfuel pump, check that the subfuel pump actually runs; when it is on, you will hear some noise if you listen to the subfuel fill port with the subfuel fill cap removed. The subfuel pump should run for 2 seconds when the ignition switch is first turned on. If the subfuel pump does not make noise, check as follows:
  1. Turn the ignition switch to LOCK (0).
  1. Turn the ignition switch to ON (II).
  1. Measure the voltage between the subfuel pump relay 4P connector terminals No. 2, No.4 and body ground individually.
Is there battery voltage?
YES -
Go to Step 5 .
NO -
  • Repair open in the wire between the subfuel pump relay and the auxiliary under-dash fuse holder (15 A) fuse. Also replace the auxiliary under-hood fuse box (15 A) fuse.■
  • Repair open in the wire between the auxiliary under-dash fuse holder (15 A) fuse and the ignition switch.■
  1. Turn the ignition switch to LOCK (0).

  1. Connect subfuel pump relay 4P connector terminal No. 3 to body ground with a jumper wire.
  1. Jump the SCS line with the HDS.
  1. Disconnect ECM/PCM connector A (49P).

  1. Check for continuity between ECM/PCM connector terminal A33 and body ground.
Is there continuity?
YES -
Go to Step 10 .
NO -
Repair open in the wire between the subfuel pump relay and the ECM/PCM (A33).■
Is the subfuel pump relay OK?
YES -
Go to Step 11 .
NO -
Replace the subfuel pump relay .■
  1. Reinstall the subfuel pump relay.
  1. Reconnect ECM/PCM connector A (49P).

  1. Turn the ignition switch to ON (II), and measure the voltage between subfuel pump relay 4P connector terminal No. 1 and body ground within 2 seconds.
Is there battery voltage?
YES -
Go to Step 14 .
NO -
  1. Turn the ignition switch to LOCK (0).

  1. Disconnect the fuel subharness 4P connector (A) from the dashboard wire harness.

  1. Turn the ignition switch to ON (II), and measure the voltage between dashboad wire harness 4P connector terminals No. 1 and No. 2 within 2 seconds.
Is there battery voltage?
YES -
Go to Step 20 .
NO -
Go to Step 18 .
  1. Turn the ignition switch to LOCK (0).

  1. Check for continuity between body ground and dashboad wire harness 4P connector terminal No. 2.
Is there continuity?
YES -
Repair open in the wire between the subfuel pump relay and the fuel subharness 4P connector.■
NO -

  1. Connect subfuel pump 4P connector terminal No. 2 to body ground with a jumper wire.

  1. Check for continuity between body ground and fuel subharness 4P connector terminal No. 1.
Is there continuity?
YES -
Go to Step 24 .
NO -
Repair open in the wire between the subfuel pump and the fuel subharness 4P connector.■

  1. Connect subfuel pump 4P connector terminal No. 4 to body ground with a jumper wire.

  1. Check for continuity between body ground and fuel subharness 4P connector terminal No. 2.
Is there continuity?
YES -
NO -
Repair open in the wire between the subfuel pump and the fuel subharness 4P connector.■