Circuit Description
The secondary fuel pump is located in the rear fuel tank. The secondary fuel pump is powered by a secondary fuel pump relay. Fuel is transferred from the rear fuel tank to the front 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 secondary fuel pump relay ground is controlled by the powertrain control module (PCM). The secondary fuel pump diagnostic runs only at idle. If the PCM commands the secondary fuel pump ON and a predetermined change in both the front and rear fuel level sensors does not occur, DTC P2636 sets.
Conditions for Running the DTC
| • | DTCs P0461, P0462, P0463, P2066, P2067, P2068 are not set. |
| • | The vehicle speed is 0 km/h (0 mph). |
| • | The engine has been idling for more than 2 minutes and 20 seconds. |
| • | The primary fuel level is less than 60 L (15.8 gal). |
| • | The secondary fuel level is more than 3 L (2.6 gal). |
Conditions for Setting the DTC
The PCM does not detect a change of 4 L (1.06 gal) in both the primary and secondary fuel level sensors with the secondary pump commanded ON for 120 seconds.
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
DTC P2636 will not illuminate the MIL, but may drive the fuel gage to E when active.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests the supply voltage circuit of the secondary fuel pump relay.
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This step verifies the secondary fuel pump operation. Listen for an audible sound as the secondary fuel pump relay harness connector is jumpered.
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This step verifies that there is adequate fuel in the rear fuel tank. The rear 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.
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This step tests for a short to voltage on the control circuit of the secondary fuel pump relay.
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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 | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | 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.
Does the test lamp illuminate when the fuel pump is commanded ON? | -- | Go to Step 3 | Go to Step 22 | |||||
3 | Probe the ignition 1 voltage circuit of the secondary fuel pump relay with a test lamp connected to a good ground. Is the test lamp illuminated? | -- | Go to Step 4 | Go to Step 12 | ||||
Connect a 15-amp fused jumper wire between the ignition 1 voltage circuit of the secondary fuel pump relay and the fuel balance pump supply voltage circuit of the secondary fuel pump relay. Does the secondary fuel pump turn ON? | -- | Go to Step 5 | Go to Step 16 | |||||
Is the fuel level sensor rear voltage above the specified value? | 1 V | Go to Step 7 | 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 fuel level sensor rear voltage decrease as the secondary fuel pump is operating? | -- | Go to Step 8 | Go to Step 18 | |||||
Does the test lamp illuminate? | -- | Go to Step 23 | Go to Step 9 | |||||
Probe the secondary fuel pump relay control circuit of the secondary fuel pump relay with a test lamp connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 27 | Go to Step 10 | |||||
Does the secondary fuel pump turn ON when the fuel pump relay control circuit jumper is grounded? | -- | Go to Step 11 | Go to Step 19 | |||||
11 | Test the secondary fuel pump relay control circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 21 | ||||
12 | Inspect the PCM 1 fuse. Is the PCM 1 fuse open? | -- | Go to Step 13 | Go to Step 25 | ||||
13 | Test the ignition 1 voltage circuit of the secondary fuel pump relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 14 | ||||
14 | Test the fuel balance pump supply voltage circuit of the secondary fuel pump for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 15 | ||||
15 |
Does the fuse in the jumper wire open? | -- | Go to Step 29 | Go to Intermittent Conditions | ||||
16 |
Is the test lamp illuminated? | -- | Go to Step 17 | Go to Step 26 | ||||
17 | Probe the ground circuit of the secondary fuel pump with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 20 | Go to Step 24 | ||||
18 | Inspect the fuel line between the primary and secondary fuel tanks for a restriction. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 29 | ||||
19 | 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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 28 | ||||
20 | Inspect for poor connections at the harness connector of the secondary fuel pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 29 | ||||
21 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 30 | ||||
22 | Repair the open in the fuel pump supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 31 | -- | ||||
23 | Repair the short to ground in the secondary fuel pump relay control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 31 | -- | ||||
24 | Repair the open in the secondary fuel pump ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 31 | -- | ||||
25 | Repair the open ignition 1 voltage circuit of the secondary fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 31 | -- | ||||
26 | Repair the open in the fuel balance pump supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 31 | -- | ||||
27 | Repair the short to voltage in the secondary fuel pump relay control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 31 | -- | ||||
28 | Replace the secondary fuel pump relay. Did you complete the replacement? | -- | Go to Step 31 | -- | ||||
29 | Replace the rear fuel sender assembly. Refer to Fuel Sender Assembly Replacement . Did you complete the replacement? | -- | Go to Step 31 | -- | ||||
30 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 31 | -- | ||||
31 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 32 | ||||
32 | Observe the Capture Info with a scan tool. Are there any DTCs that are not diagnosed? | -- | System OK | |||||
