For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
The Fuel Quantity Solenoid (FQS) works in tandem with the Fuel Pressure Regulator (FPR) to control fuel volume and pressure in the Fuel Rail. The FQS is positioned in the inlet side of the High Pressure Delivery Pump (HPDP). The FQS receives 12 Volts from the Totally Integrated Power Module (TIPM) and a duty-cycle ground signal from the Powertrain Control Module (PCM). The FQS is normally open, so when the FQS is not actuated (no ground signal from the PCM), the HPDP inlet passage is open allowing full fuel flow to the pumping chambers inside the HPDP. When the PCM grounds the FQS control signal the FQS closes the fuel inlet passage, preventing fuel from entering the pumping chambers. The FPR is positioned at the return passage of the Fuel Rail. The solenoid receives 12 Volts from the TIPM and a duty-cycle ground signal from the PCM. The FPR is normally open and when the solenoid is not actuated (no ground signal from the PCM), the Fuel Rail return passage opens allowing fuel pressure in the rail to escape into the return circuit and on to the Fuel Tank. When the PCM grounds the FPR control signal, the solenoid valve closes allowing fuel pressure to build in the rail. The Fuel Pressure Regulator is not serviceable separate of the Fuel Rail Assembly.
When Monitored:
With the ignition on and the Fuel Pressure Regulator command on.
Set Condition:
The PCM detects excessive current on the (K646) Fuel Pressure Regulator Control circuit for 0.28 second.
Possible Causes
(K646) FUEL PRESSURE REGULATOR CONTROL CIRCUIT SHORTED TO VOLTAGE
(K646) FUEL PRESSURE REGULATOR CONTROL CIRCUIT SHORTED TO THE (F342) FUSED ASD RELAY 2 OUTPUT 12-VOLT SUPPLY CIRCUIT
3.
CHECK FOR THE (K646) FUEL PRESSURE REGULATOR CONTROL CIRCUIT SHORTED TO THE (F342) FUSED ASD RELAY 2 OUTPUT 12-VOLT SUPPLY CIRCUIT
1.
Turn the ignition off.
2.
Disconnect the TIPM C5 harness connector.
3.
Remove the jumper wire and install the ASD Relay.
4.
Measure the resistance between the (K646) Fuel Pressure Regulator Control circuit and the (F342) Fused ASD Relay 2 Output 12-Volt Supply in the Fuel Pressure Regulator harness connector.
4.
CHECK THE (K646) FUEL PRESSURE REGULATOR CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1.
Disconnect the PCM C1 harness connector.
2.
Measure the resistance of the (K646) Fuel Pressure Regulator Control circuit between the Fuel Pressure Regulator harness connector and the PCM C1 harness connector.
Reconnect the Fuel Pressure Regulator harness connector.
2.
Reconnect the TIPM C5 harness connector.
3.
Reconnect the Powertrain Control Module C1 harness connector.
4.
Turn the ignition on.
5.
With the scan tool, erase DTCs.
6.
Turn the ignition off.
7.
Disconnect the Fuel Pressure Regulator harness connector.
8.
Turn the ignition on.
9.
With the scan tool, select View DTCs.
10.
Connect a jumper between the (K646) Fuel Pressure Regulator Control circuit and ground.
NOTE:
The scan tool should display a P0090-FUEL PRESSURE CONTROL CIRCUIT OPEN DTC with the connector unplugged and a P0091-FUEL PRESSURE CONTROL CIRCUIT LOW DTC with the jumper in place.
Did the scan tool display the DTCs as described above?
Yes
Replace the Fuel Pressure Regulator in accordance with the service information.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Fuel Pressure Regulator 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.
Perform any Technical Service Bulletins that may apply.
