Circuit Description
The fuel pump is located on the left frame rail between the fuel tanks. The engine control module (ECM) provides ignition positive voltage to the coil side of the fuel pump relay. The ECM energizes the fuel pump relay, which applies power to the fuel transfer pump. 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 engine. If the ECM commands the transfer fuel pump ON and a predetermined change in the front and rear fuel level sensors does not occur, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2636 Fuel Pump 2 Flow Insufficient
Conditions for Running the DTC
| • | DTC P0500 is not set. |
| • | The engine is running. |
| • | The vehicle speed is 0 km/h (0 mph). |
| • | The primary fuel level is less than 25 liters (6.6 gallons). |
| • | The secondary fuel level is between 3-10 liters (0.8-2.6 gallons). |
| • | The above conditions are met for 20 seconds before the fuel transfer pump is commanded ON. |
| • | The fuel transfer pump is commanded ON for 120 seconds. |
Conditions for Setting the DTC
The ECM detects a primary fuel level increase and a secondary fuel level decrease of less than 2.6 liters (0.70 gallons) each, within 120 seconds.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
| • | The fuel gage will be commanded to empty. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
| • | When outside temperatures are below 0°C (32°F), the fuel tank pickup screen may ice over from water in the fuel tank. |
| • | If the engine is running while fueling the vehicle, this DTC may set. |
| • | The fuel will default to empty when this DTC sets. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the condition is on the coil side or the switch side of the fuel pump relay.
-
This step verifies the fuel transfer pump operation. If the test lamp flashes, the fuel transfer pump and circuits are OK.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
2 | Is DTC P0461, P0462, P0463, P2067, or P2068 also set? | -- | Go to Step 3 | |||||
|
Important: The fuel level must be between 25-50 percent in order to perform this diagnostic procedure. If the fuel level is not within this range, misdiagnosis will occur.
Does the fuel pump relay click? | -- | Go to Step 9 | Go to Step 4 | |||||
4 |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 25 | ||||
5 |
Does the test lamp turn ON and OFF? | -- | Go to Step 22 | Go to Step 6 | ||||
6 | Does the test lamp remain illuminated? | -- | Go to Step 7 | Go to Step 8 | ||||
7 | Test the fuel pump relay control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 24 | ||||
8 | Test the fuel pump relay control circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 24 | ||||
9 | Command the fuel transfer pump ON with a scan tool. Does the fuel transfer pump operate? | -- | Go to Step 17 | Go to Step 10 | ||||
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 12 | ||||
Connect a fused jumper wire between the fuel pump relay battery voltage circuit and the fuel pump supply voltage circuit. Does the fuel pump operate? | -- | Go to Step 22 | Go to Step 15 | |||||
12 | Is the battery positive voltage fuse open? | -- | Go to Step 13 | Go to Step 27 | ||||
13 | Test the battery voltage circuit of the fuel pump relay for a short to ground. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 14 | ||||
14 | Test the fuel pump supply voltage circuit for a short to ground. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 23 | ||||
15 | Test the fuel transfer pump supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 16 | ||||
16 | Probe the ground circuit of the fuel transfer pump with a test lamp that is connected to battery voltage. Does the test lamp illuminate? | -- | Go to Step 23 | Go to Step 26 | ||||
17 | Observe the fuel level sensor rear tank voltage parameter with a scan tool. Is the voltage more than the specified value? | 1 V | Go to Step 19 | Go to Step 18 | ||||
18 | Add the specified amount of fuel to the rear fuel tank. Did you complete the action? | 19 L (5 gal) | Go to Step 19 | -- | ||||
19 |
Does the rear fuel level sensor voltage parameter decrease as the fuel pump is operating? | -- | Go to Step 20 | Go to Step 21 | ||||
20 |
Does the fuel volume measure more than the specified value? | 2.6 L (0.70 gal) | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 21 | ||||
21 | Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 29 | ||||
22 | Inspect for poor connections at the harness connector of the 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 31 | Go to Step 28 | ||||
23 | Inspect for poor connections at the harness connector of the fuel transfer pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 29 | ||||
24 | Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 30 | ||||
25 | Repair the open ground circuit of the fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 31 | -- | ||||
26 | Repair the open ground circuit of the fuel transfer pump. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 31 | -- | ||||
27 | Repair the open battery voltage circuit of the fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 31 | -- | ||||
28 | Replace the fuel pump relay. Did you complete the replacement? | -- | Go to Step 31 | -- | ||||
29 | Replace the fuel transfer pump. Refer to Fuel Pump Replacement . Did you complete the replacement? | -- | Go to Step 31 | -- | ||||
30 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 31 | -- | ||||
31 |
Did the DTC fail this ignition? | -- | Go to Diagnostic Aids | Go to Step 32 | ||||
32 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
