P0091 - FUEL PRESSURE 1 CONTROL CIRCUIT LOW
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The Fuel Pressure Solenoid (FPS) is a solenoid operated valve designed to regulate fuel pressure in the fuel rail. The FPS valve is positioned in the in-line with the outlet passage of the high
pressure fuel rail. The solenoid receives 12 volt power and a duty-cycle ground signal from the ECM. When the solenoid is not actuated (no ground signal from the ECM), the fuel rail outlet passage opens
allowing fuel pressure in the rail to escape into the return circuit to the fuel tank. When the ECM grounds the FPS control signal, the solenoid valve closes allowing fuel pressure to build in the rail.
Possible Causes
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INTERMITTENT DTC
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(K370) FUEL PRESSURE SOLENOID CONTROL CIRCUIT SHORTED TO GROUND
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(K370) FUEL PRESSURE SOLENOID CONTROL CIRCUIT OPEN OR HIGH RESISTANCE
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(K369) FUEL PRESSURE SOLENOID 12 VOLT SUPPLY CIRCUIT OPEN OR HIGH RESISTANCE
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FUEL PRESSURE SOLENOID
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ENGINE CONTROL MODULE (ECM)
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Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
Diagnostic Test
1.
DTC IS ACTIVE
Ignition on, engine not running.
With the scan tool, Clear DTCs in the Engine Control Module (ECM).
With the scan tool, actuate the Fuel Pressure Solenoid at 100%.
Monitor the scan tool for at least two minutes.
With the scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
No
2.
(K370) FUEL PRESSURE SOLENOID CONTROL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the Fuel Pressure Solenoid harness connector.
Disconnect the Engine Control Module (ECM) harness connector.
Measure the resistance between ground and the (K370) Fuel Pressure Solenoid Control circuit in the Fuel Pressure Solenoid harness connector.
Is the resistance above 1000 ohms?
Yes
No
3.
(K370) FUEL PRESSURE SOLENOID CONTROL CIRCUIT OPEN OR HIGH RESISTANCE
Measure the resistance of the (K370) Fuel Pressure Solenoid Control circuit between the Fuel Pressure Solenoid harness connector and the Engine Control Module (ECM) harness connector.
Is the resistance below 10.0 ohms?
Yes
No
4.
(K369) FUEL PRESSURE SOLENOID 12 VOLT SUPPLY CIRCUIT OPEN OR HIGH RESISTANCE
Measure the resistance of the (K369) Fuel Pressure Solenoid 12 Volt Supply circuit between the Fuel Pressure Solenoid harness connector and the Engine Control Module (ECM) harness connector.
Is the resistance below 10.0 ohms?
Yes
No
5.
ASD RELAY OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE
Remove the ASD Relay.
Connect a jumper wire between cavity 30 and cavity 87 in the ASD Relay connector.
Using a 12-volt test light connected to ground, check the ASD Relay Output circuit in ECM harness connector C2 cavities 1, 3 and 5.
Did the test light illuminate for each circuit?
Yes
No
6.
FUEL PRESSURE SOLENOID
Connect the Engine Control Module (ECM) harness connector.
Turn the ignition on.
With the scan tool, actuate the Fuel Pressure Solenoid to 100%.
Using a 12 volt test light connected to 12 volts, check the (K370) Fuel Pressure Solenoid Control circuit in the Fuel Pressure Solenoid harness connector.
NOTE:
The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
NOTE:
The circuit will remain actuated by the controller for 30 seconds. Be certain the actuation is active when checking the circuit.
With the scan tool, actuate the Fuel Pressure Solenoid to 0%.
Using a 12 volt test light connected to 12 volts, check the (K370) Fuel Pressure Solenoid Control circuit in the Fuel Pressure Solenoid harness connector.
NOTE:
The test light should not be illuminated.
NOTE:
The circuit will remain actuated by the controller for 30 seconds. Be certain the actuation is active when checking the circuit.
Is the test light illuminated and bright with the actuation at 100% and not illuminated with the actuation at 0%?
Yes
No
7.
ENGINE CONTROL MODULE (ECM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Fuel Pressure Solenoid and the Engine Control Module (ECM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Refer to any Technical Service Bulletins that may apply.
Were any problems found?
Yes
No