P0457
P0457-LOOSE FUEL CAPP0457-Loose Fuel Cap:
Theory of Operation
The PCM records the fuel level when the ignition key is turned off and then again when the ignition key is turn back on. This is done to monitor for fuel level increase. If a fuel level increase is detected and the EVAP Leak monitor is run and fails, the Loose Gas Cap DTC will set and the GAS CAP indicator will displayed in odometer to inform the vehicle operator that the cap is off of loose.
WHEN MONITORED
Ignition on. Ambient Temperature between 4° C and 32° C (39° F and 89° F) Close Loop fuel system. Test runs after the medium leak test is inconclusive and the PCM has senses a fuel increase.
SET CONDITION
The PCM activates the EVAP Purge Solenoid to pull the EVAP system into a vacuum to close the NVLD switch. Once the NVLD switch is closed, the PCM turns the EVAP Purge Solenoid off to seal the EVAP system. If the NVLD switch reopens before the calibrated amount of time after a fuel tank fill, an error is detected. Two Trip Fault. Three good trips to turn off the MIL.
POSSIBLE CAUSES
- Loose or missing fuel cap
- Fuel fill cap
- EVAP purge system medium leak
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. VEHICLE HISTORY AND SERVICE BULLETIN INVESTIGATION
Ignition on, engine not running.
With a scan tool, read DTCs and record the related Freeze Frame data if any DTC(s) are present.
Whether or not any DTC(s) are present you will want to check the following items which may assist in repairing the customer's complaint successfully.
Check the vehicles repair history.
If the vehicle has a repair history that pertains to the customer's current complaint, review the repair.
Inspect the vehicle for any aftermarket accessories that may have been installed incorrectly.
Check for any service bulletin(s) related to the customer's complaint or DTC(s).
If a service bulletin applies, follow the instructions per the service bulletin.
Choose the following scenario that best applies.
The service bulletin repaired the customer's complaint.
Testing complete.
A DTC is present, no service bulletins apply, or the service bulletin didn't repair the customer's complaint.
Go To 2.
2. ACTIVE DTC
Ignition on, engine not running.
With a scan tool, read DTCs.
Q: Is the DTC active at this time?
YES: Go To 3.
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
3. LOOSE OR MISSING FUEL FILL CAP
Perform a visual and physical inspection of the Fuel Fill Cap and the fill tube.
- Improper installation of the Fuel Fill Cap
- Loose or missing Fuel Filler Cap
- Holes or Cracks
- Damaged Locking tabs on Cap and/or fill tube
- Damaged seal points on Cap and/or fill tube
- Fuel Fill Cap gasket seal
Q: Were any of the above conditions found?
YES: Repair or replace the fuel fill cap or fill tube as necessary. Ensure proper fuel fill cap installation. Once the repair is complete continue to step 4. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 4.
4. NVLD SERVICE TEST
With the scan tool perform the NVLD Service Test.
Q: Does the NVLD Service Test pass?
YES: Test complete. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 5
5. VERIFY EVAPORATIVE EMISSION LEAK
To continue testing you will need Miller Tool #8404A Evaporative Emission Leak Detector (EELD).
WARNING: KEEP LIT CIGARETTES, SPARKS, FLAMES, AND OTHER IGNITION SOURCES AWAY FROM THE TEST AREA TO PREVENT THE IGNITION OF EXPLOSIVE GASES. KEEP THE TEST AREA WELL VENTILATED.
NOTE: The fuel tank should have between 20% and 80% of fuel tank capacity to properly test the EVAP system.
Connect the red power lead of the EELD to the battery positive terminal and the black ground lead to battery negative terminal.
Block the vent hose of the canister if using the service port. Connect shop air to the EELD.
Set the smoke/air control switch to AIR.
Insert the tester's AIR supply tip (clear hose) into the appropriate calibration orifice on the tester's control panel (based on DTC leak size).
Press the remote smoke/air start button.
Position the red flag on the air flow meter so it is aligned with the indicator ball.
When the calibration is complete, release the remote button. The EELD flow meter is now calibrated in liters per minute to the size leak indicated by the DTC set in the PCM.
Install the service port adapter #8404-14 on the vehicle's service port and block the vent hose of the EVAP Canister (if equipped) or install the #8404-ADP service adaptor into the filter line.
Connect the Air supply hose from the EELD to the service port (if equipped) or to the #8404-ADP adapter.
Press the remote button to activate AIR flow.
NOTE: Larger volume fuel tanks, lower fuel levels or if the vehicle is equipped with a Flow Management Valve may indicate high flow and will require 4 to 5 minutes to fill.
Compare the flow meter indicator ball reading to the red flag.
ABOVE the red flag indicates a leak present.
BELOW the red flag indicates a sealed system.
Q: Is the indicator ball above the red flag?
YES: Go To 6.
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
6. EVAPORATIVE EMISSION LEAK DETECTION
NOTE: A thorough visual inspection of the EVAP system hoses, tubes, and connections may save time in your diagnosis. Look for any physical damage or signs of wetness at connections. The strong smell of fuel vapors may also aid diagnosis.
To continue testing, you will need Miller Tool #8404A Evaporative Emissions Leak Detector (EELD).
Remove the Air supply hose from the service port (if equipped) or from the #8404-ADP adapter. Connect the SMOKE supply tip (black hose) to the service port (if equipped) or to the #8404-ADP adapter. Set the smoke/air control switch to SMOKE.
NOTE: The flow meter indicator ball will not move in the smoke mode.
Press the remote smoke/air start button.
NOTE:
- Make sure that smoke has filled the EVAP system by continuing to press the remote smoke/air start button, remove the vehicle fuel cap, and wait for the smoke to exit. Once smoke is indicated reinstall the fuel cap.
- For optimal performance, introduce smoke into the system for an additional 60 seconds; continue introducing smoke at 15 second intervals, as necessary.
While still holding the remote smoke/air start button, use the white light (#8404-CLL) to follow the EVAP system path, and look for the source of the leak indicated by exiting smoke.
If a leak is concealed from view (i.e., top of fuel tank), release the remote smoke/air start button, and use the ultraviolet (UV) black light #8404-UVL and the yellow goggles 8404-20 to look for residual traces of dye that is left behind by the smoke.
The exiting smoke deposits a residual fluid that is either bright green or bright yellow in color when viewed with a UV light.
NOTE: The EVAP System is divided into three zones. A leak from any of these zones can cause this DTC to set. The lists below specify the possible leak points in that specific zone. For further assistance see the Zone Identification Chart below.
ZONE 1
1. Fuel Cap
2. Recirculation Check Valve.
3. Vapor Recirculation Line.
4. Signal Vapor Line for FVM.
5. Flow Management Valve.
6. Fuel Tank to Canister Vapor Line connection.
7. Fuel Tank Vent (Check Valve).
8. Vapor Line to Canister.
9. Flow Control Orfice.
10. Control Valve.
11. Liquid Trap.
12. Fuel Tank.
13. Check valve.
14. Fuel Fill Tube to Tank connector.
15. Fuel Fill Tube
Damaged or disconnected EVAP system components.
ZONE 2
1. Filter.
2. NVLD.
3. Canister Vent Line.
4. EVAP Canister.
5. Chassis Purge Valve.
6. Fuel Tank to Canister Vapor Line connection.
7. EVAP Purge connection.
ZONE 3
1. EVAP Purge Vacuum Line.
2. Connection to Chassis Line.
3. Connection to Canister.
4. Chassis Purge Line.
5. EVAP Purge Vacuum Line.
6. Connection to EVAP Purge Harness.
7. Chassis EVAP Purge Line connection to Engine Vacuum.
8. EVAP Purge Valve.
9. Service Port.
NOTE: Carefully inspect the vent side of the EVAP Canister. Due to the filtering system in the canister the smoke may not be as thick. Introducing smoke into the filtered side of the canister may assist in locating the leak.
Q: Was a leak found?
YES: Go To 7.
NO: Go To 8.
7. LEAK AT GAS CAP
Remove the SMOKE supply tip (black hose) from the service port (if equipped) or to the #8404-ADP adapter. Install gas cap adapter, Miller Tool #8382 (1/4 turn cap) or #6922 (screw cap) and #8399 (secondary seal depressor) and repeat test 5.
Q: Was a leak found at the gas cap adapter?
YES: Replace the Fuel Filler tube assembly. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Replace the gas cap. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
8. EVAP PURGE SOLENOID OPERATION
NOTE: After disconnecting the EVAP Purge Solenoid vacuum connections, inspect the lines and solenoid for any signs of contamination from the EVAP Canister. This may indicate a faulty check valve. Replace/repair as necessary.
Turn the ignition off.
Disconnect the vacuum hoses at the EVAP Purge Solenoid.
Press the remote smoke/air start button on the EELD.
While holding the remote smoke/air start button, check to see if smoke is exiting the purge valve. This indicates that there is a leak internal to the purge valve.
NOTE: Below is an optional method of checking the purge valve for leaks if the EELD is unavailable.
Turn the ignition off.
Disconnect the vacuum hoses at the EVAP Purge Solenoid.
Using a hand vacuum pump, apply 10 in Hg to the "CAN" of the EVAP Purge Solenoid.
NOTE: Monitor the vacuum gauge for at least 15 seconds.
Q: Is smoke visible from the EVAP Purge Solenoid if using the EELD, or not hold a vacuum?
YES: Go To 9.
NO: Replace the EVAP Purge Solenoid. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
9. NVLD SWITCH OPERATION
Reconnect all vacuum hoses.
Start the engine.
Allow the engine to idle.
Using the scan tool, perform the NVLD FORCED MONITOR TEST.
Monitor the NVLD Switch.
NOTE: As the test runs, the NVLD Switch should go from an OPEN state to CLOSED. After the vacuum is released form the EVAP system the Switch state will return to OPEN.
Q: Did the NVLD Switch operate as described above?
YES: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
NO: Replace the NVLD Assembly. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test