P128F

P128F-FUEL PUMP - LOW SPEED MODE PERFORMANCE - HEV





For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams

Theory of Operation

The purpose of the Dual Speed Fuel Pump (DSFP) feature is to reduce electrical demand by lowering the current draw of the fuel pump when the fuel flow rate is low. The DSFP uses the normal fuel pump relay circuitry with an additional relay to switch a resistor (voltage divider) into the circuit. Switching the resistor (low speed) into the circuit will reduce the fuel pump voltage from roughly 14v to 10v. The diagnostic uses a feedback from the input voltage to the pump. The desired state is then compared against the actual state to evaluate whether or not the circuitry is performing appropriately.

- When Monitored:
Vehicle is in ready mode, battery voltage 10.4

- Set Condition:
The Powertrain Control Module (PCM) compares the circuit feedback to a calibrated range (Greater than 0.726 volt Less than 0.59 of a volt) when the circuit is energized.





WARNING: On vehicles equipped with the high voltage system, you must thoroughly read and follow all High Voltage Safety procedures. In addition, before performing any diagnostic or service procedure near a high voltage component, you must perform the High Voltage Power Down. Failure to follow these instructions may result in possible serious or fatal injury

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Pre-Diagnostic Troubleshooting Procedure.

1. DTC IS ACTIVE
1. Turn the ignition on.
2. With the scan tool, Clear DTCs in the Powertrain Control Module (PCM).
3. With the scan tool, actuate the DSFP relay.
4. With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. DUAL SPEED FUEL PUMP RELAY
1. Turn the ignition off.
2. Remove the DSFP relay from the PDC.
3. Measure the resistance of the DSFP relay coil.

Is the resistance between 70 to 90 Ohms?

Yes

- Go To 3

No

- Verify that there is good pin to terminal contact in the Fuel Pump Module, Relay and Powertrain Control Module connectors. If OK, replace the Fuel Pump Relay.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. (K317) DSFP VOLTAGE REDUCER CIRCUIT OPEN OR HIGH RESISTANCE




1. Disconnect the C3 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals, resulting in poor terminal to pin connection. Install the PCM Pinout Box 8815 to perform diagnosis.

2. Measure the resistance of the (K317) DSFP voltage reducer circuit from the relay connection to the appropriate terminal of PCM Pinout Box 8815.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the (K317) DSFP voltage reducer circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. (N1) FUEL PUMP RELAY OUTPUT CIRCUIT SHORTED TO VOLTAGE




1. Turn the ignition on
2. Measure the voltage of the (N1) circuit at the Relay connection.

Is the voltage above 1.0 volt?

Yes

- Repair the short to voltage on the (N1) fuel pump relay output circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 5

5. DSFP RESISTOR SHORTED




1. Turn the ignition off.
2. Disconnect DSFP Resistor harness connector.
3. Measure the resistance of the DSFP Resistor.

Is the resistance 0.4 of an Ohm?

Yes

- Go To 6

No

- Replace the DSFP Resistor assembly.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Short Runner Valve Assembly and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Search for any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.