Diagnostic Instructions
DTC Descriptor
DTC P2635 00: Fuel Pump Flow Performance
Circuit/System Description
The engine control module (ECM) supplies a high voltage signal to the fuel pump flow control module (FPCM) when the ECM detects that the ignition is on. The high voltage signal from the ECM to the FPCM remains active for two seconds, unless the engine
is in crank or run. While this signal is being received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.
Conditions for Running the DTC
| • | DTC P0191, P0192, P0193, P0231, P0232, P023F, P064A, P1255 or P06A6 are not active. |
| • | DTC P0641 has not failed this ignition cycle. |
| • | Fuel pump control is enabled and the fuel pump control state is normal. |
| • | The system voltage is greater than 11 volts. |
| • | The engine has been running for more than 30 seconds. |
Conditions for Setting the DTC
This DTC sets when the FPCM detects a predetermined fuel pressure performance degradation between the desired fuel rail pressure and the current estimated fuel rail pressure.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The FPCM records the operating conditions at the time the diagnostic fails. The FPCM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | A last test failed, or the current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic. |
Diagnostic Aids
Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine
how many ignition cycles that the diagnostic test reported a pass and/or a fail.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Engine Controls Connector End Views
Description and Operation
Fuel System Description
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
Important: Verify that P0192, P0193, P0231, P0232, or P023F are not set as current or history before performing this diagnostic. If any of those codes are set as current or history, go to
DTC P0192 or P0193
or
DTC P0231, P0232, or P023F
.
- Ignition OFF, disconnect the harness connector at the fuel tank pump module.
- Ignition ON, test for 1.0 ohm or less between the fuel pump module low reference circuit terminal A and ground.
| ⇒ | If greater than the specified range, test the fuel pump module low reference circuit for an open/high resistance. If the circuit tests normal, replace the FPCM. |
- Ignition OFF, install a test lamp between the control circuit terminal D and the low reference circuit terminal A.
- Ignition ON, command the fuel pump ON and OFF with a scan tool. The test lamp should trun ON and OFF when changing between the commanded states.
| ⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests mormal, replace the FPCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM. |
- Perform the
Fuel System Diagnosis
to verify proper fuel pressure.
| ⇒ | If the fuel pressure is not normal, replace the fuel tank fuel pump module. |
- If all circuits test normal, replace the FPCM.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
