Fuel Pump Electrical Circuit Diagnosis
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Fuel Pump Electrical Circuit Diagnosis
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Diagnostic Fault Information
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Fuel Pump Relay Ignition Voltage
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*
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P0627 00**
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-
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-
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Fuel Pump Motor Supply Voltage
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*
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**
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***
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-
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Fuel Pump Relay Control
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P0628 00**
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P0627 00**
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P0629 00***
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-
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Fuel Pump Relay Ground
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-
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**
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-
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-
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Fuel Pump Ground
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-
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**
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-
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-
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* The fuel pump fuse opens and the engine cranks but does not run.
** The engine cranks but does not run.
*** The fuel pump operates continuously and the battery will discharge.
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Circuit/System Description
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When you turn ON the ignition switch, the engine control module (ECM) energizes the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the ECM receives ignition reference pulses. If there are no ignition reference pulses, the ECM shuts the fuel pump OFF within 2 s after the ignition was switched to the ON position or if the engine stops.
The following conditions may cause the fuel pump fuse to open:
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There is an intermittent short to ground in the supply voltage circuit of the fuel pump.
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•
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The fuel pump has an intermittent internal condition.
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Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Special Tools
EL 43244
Relay Puller Pliers
For equivalent regional tools, refer to
Special Tools
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Circuit/System Verification
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1.
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Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. You should hear and feel a click when you command the fuel pump relay ON and OFF.
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2.
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Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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1.
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Ignition OFF, the fuel pump should not be running.
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2.
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If the fuel pump runs continuously, test the fuel pump motor supply voltage circuit for a short to voltage. If the circuit tests normal, replace the fuel pump relay.
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3.
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Ignition OFF, remove the KR23A Fuel Pump Relay from the X50A Fuse Block - Underhood Primary with the
EL 43244
Relay Puller Pliers.
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4.
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Test for less than 5 Ω between the ground circuit terminal 85 and ground.
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5.
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If greater than the specified range, repair the ground circuit for an open/high resistance.
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6.
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Ignition ON, verify a test lamp illuminates between the relay switch ignition circuit terminal 30 and ground.
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7.
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If the test lamp does not illuminate, repair the ignition circuit for a short to ground or an open/high resistance. Replace the fuse if necessary.
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8.
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Connect a 15 A fused jumper wire between the relay switch ignition circuit terminal 30 and the relay switch supply circuit terminal 87. The fuel pump should turn ON.
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9.
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If the fuel pump does not turn ON, test for the following conditions:
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•
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An open/high resistance in the relay switch supply circuit
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•
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An open/high resistance in the G12 Fuel Pump ground circuit
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10.
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If the above circuits test normal, replace the G12 Fuel Pump.
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11.
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Ignition OFF, connect a test lamp between the relay coil control circuit terminal 86 and ground.
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12.
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Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF with each command.
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13.
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If the test lamp is always ON, test the relay coil control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
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14.
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If the test lamp is always OFF, test the relay coil control circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the K20 Engine Control Module.
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15.
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If all circuits test normal, test or replace the KR23A Fuel Pump Relay.
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Relay Test
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1.
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Ignition OFF, remove the fuel pump relay from the electrical center with the
EL 43244
Relay Puller Pliers.
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2.
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Test for 70-110 Ω between terminals 85 and 86.
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3.
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If not within the specified range, replace the KR23A Fuel Pump Relay
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4.
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Test for infinite resistance between the following terminals:
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5.
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If not the specified value, replace the KR23A Fuel Pump Relay.
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6.
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Install a 20 A fused jumper wire between terminal 85 and B+. Install a jumper wire between terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
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7.
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If greater than the specified range, replace the KR23A Fuel Pump Relay.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Fuel Sender Assembly Replacement
