Component Tests and General Diagnostics
Fuel System Diagnosis
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.
Circuit/System Description
The engine control module (ECM) supplies a high voltage signal to the fuel pump 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 2 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.
Reference Information
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Programming and Relearningfor scan tool information
Special Tools
* CH-48027 Fuel Pressure Gauge
* J 37287 Fuel Line Shut-Off Adapters
Circuit/System Verification
Important:
* Repair all fuel system related DTCs before performing this diagnostic.
* Inspect the fuel system for damage or external leaks before proceeding.
* Verify that adequate fuel is in the fuel tank before proceeding.
* The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
* Before proceeding with this test review the User Manual CH 48027-5 for safety information and instructions.
1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description Hybrid Modes of Operation.
2. Ignition ON, verify the scan tool hood position parameter displays OPEN
• If the hood position does not display OPEN, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
3. Ignition OFF, all accessories OFF, install the CH-48027 . Refer to Fuel Pressure Gauge Installation and Removal Fuel Pressure Gauge Installation and Removal.
4. Ignition ON, command the fuel pump Enable ON with a scan tool. Verify the fuel pressure is between 345-414 kPa (50-75 psi) and remains steady for 5 minutes.
Circuit/System Testing
Important:
* The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
* DO NOT start the engine.
1. Ignition ON, command the fuel pump Enable ON with a scan tool and observe the fuel pressure gauge while the fuel pump is operating. Verify the fuel pressure is between 345-414 kPa (50-75 psi).
• If the fuel pressure is less than the specified range, remove the fuel tank and test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump.
* Restricted fuel feed pipe
* Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.
2. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
• If the fuel pressure decreases more than the specified value, perform the following procedure:
1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief Service and Repair.
2. Install the J 37287 between the fuel feed pipe and the fuel rail.
3. Open the valve on the J 37287 .
4. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the fuel pressure gauge.
5. Close the valve on the J 37287 .
6. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
• If the fuel pressure drops, locate and replace the leaking fuel injector.
7. If the fuel system test normal, replace the fuel pump.
3. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 minutes.
• If the fuel pressure decreases more than the specified value, replace the fuel pump.
4. Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027 . The fuel pressure should not drop off during accelerations, cruise or hard cornering.
• If the fuel pressure drops off, test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump module.
5. If the fuel system components test normal, refer to Symptoms - Engine Controls Symptoms - Engine Controls.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Injector Replacement Removal and Replacement
* Fuel Tank Fuel Pump Module Replacement Fuel Tank Fuel Pump Module Replacement