Circuit Description
Important: If you were not referred to this test from another diagnostic, DO NOT perform this procedure.
The secondary fuel pump is externally located on the back of the body crossmember. The fuel pump is powered by a secondary fuel pump relay. Fuel is transferred from the secondary fuel tank to the primary fuel tank in order to ensure all of the usable fuel volume is available to the primary fuel pump. The secondary fuel pump relay supply voltage is received from the primary fuel pump relay when the primary fuel pump is energized. The control module supplies ground to the secondary fuel pump relay which energizes the secondary fuel pump.
Conditions For Running the Secondary Fuel Pump
Enabling Criteria
| • | DTCs P0461, P0462, P0463, P1431, P1432, P1433 are not active. |
| • | The fuel level sensor parameter is less than 2.4 volts. |
| • | The fuel level sensor rear parameter is more than 0.9 volts. |
| • | The fuel level sensor parameter is less than 1.4 volts with the pump running. |
| • | The secondary transfer pump has not run for 5 seconds. |
| • | The primary fuel pump is commanded ON. |
Disabling Criteria
| • | DTCs P0461, P0462, P0463, P1431, P1432, P1433 are not active. |
| • | The fuel level sensor parameter is more than 1.75 volts. |
| • | The fuel level sensor rear is less than 0.9 volts for 2 minutes. |
| • | If a predetermined time limit is reached of running the pump, the pump will not run again during the same key cycle. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests the fuel pump supply voltage circuit of the secondary fuel pump relay. The test lamp should illuminate as the primary fuel pump is commanded ON.
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This step verifies the secondary fuel pump operation.
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This step verifies that there is adequate fuel in the secondary fuel tank. The secondary fuel tank sensor voltage must be above 1 volt in order to continue.
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This step tests the secondary fuel pumps ability to transfer fuel. The rear fuel level sensor voltage should decrease while the secondary fuel pump is ON.
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This step tests for a short to ground on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to ground is indicated.
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This step tests for a short to voltage on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to voltage is indicated.
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This step verifies the secondary fuel pump relay operation. An audible click should be heard as the secondary fuel pump relay control circuit is grounded. The secondary fuel pump should turn ON as the fuel pump relay control circuit is grounded.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
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Important: The fuel level must be between 25-50 percent to perform this diagnostic procedure. If the fuel level is not within this range, misdiagnosis will occur.
Important: The circuit will be energized for approximately 2 seconds. Does the test lamp illuminate when the fuel pump is commanded ON? | -- | Go to Step 3 | Go to Step 18 | |
3 |
Does the test lamp illuminate when the fuel pump is commanded ON? | -- | Go to Step 4 | Go to Step 18 |
Important: The circuit will be energized for approximately 2 seconds. Does the secondary fuel pump turn ON? | -- | Go to Step 5 | Go to Step 12 | |
Is the rear fuel level sensor voltage more than the specified value? | 1 V | Go to Step 8 | Go to Step 6 | |
6 | Add the specified amount of fuel to the fuel tank. Did you complete the action? | 19 L (5 Gal) | Go to Step 7 | -- |
Does the secondary fuel level sensor voltage decrease as the secondary fuel pump is operating? | -- | Go to Step 8 | Go to Step 14 | |
Does the test lamp illuminate? | -- | Go to Step 19 | Go to Step 9 | |
Probe the secondary fuel pump relay control circuit with a test lamp connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 23 | Go to Step 10 | |
Does the secondary fuel pump turn ON when the fuel pump relay is commanded ON with the scan tool? | -- | Go to Step 11 | Go to Step 15 | |
11 | Test the secondary fuel pump relay control circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 17 |
12 |
Does the test lamp illuminate when the fuel pump is commanded ON? | -- | Go to Step 13 | Go to Step 22 |
13 | Probe the ground circuit of the secondary fuel pump with a test lamp connected to battery voltage. Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 20 |
14 | Inspect the fuel line between the primary and secondary fuel tanks for a restriction. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 25 |
15 | Inspect for poor connections at the harness connector of the secondary fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 24 |
16 | Test for an intermittent and for a poor connection at the secondary fuel pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 25 |
17 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 26 |
18 | Repair the open fuel pump supply voltage circuit of the secondary fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 27 | -- |
19 | Repair the short to ground in the fuel pump relay control circuit of the secondary fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 27 | -- |
20 | Repair the open ground circuit of the secondary fuel pump. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 27 | -- |
21 | Repair the open fuel pump supply voltage circuit of the secondary fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 27 | -- |
22 | Repair the open supply voltage circuit of the secondary fuel pump. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 27 | -- |
23 | Repair the short to voltage on the control circuit of the secondary fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 27 | -- |
24 | Replace the secondary fuel pump relay. Refer to Relay Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- |
25 | Replace the secondary fuel pump assembly. Refer to Fuel Pump Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- |
26 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 27 | -- |
27 |
Did you correct the condition? | -- | Go to Step 28 | Go to Step 2 |
28 | Observe the Capture Info with a scan tool. Are there any DTCs that are not diagnosed? | -- | System OK | |
