P0456
P0456-EVAP SYSTEM SMALL LEAK
For a complete wiring diagram Consult Diagrams/Electrical.
- When Monitored:
With the ignition off, fuel level less than 88%, ambient temperature between 4° C and 43° C (39° F and 109° F), and the fuel system in closed loop.
- Set Condition:
As temperatures change, a vacuum is created in the fuel tank and EVAP system. With the EVAP system sealed, the PCM monitors the NVLD switch. If the NVLD switch does not close within a calibrated time, an error is detected by the PCM. One Trip Fault. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.
Diagnostic Test
1. EVAP SYSTEM PRETEST
Ignition on, engine not running.
With a scan tool, select View DTCs. Record the Freeze Frame data if any DTC(s) are present.
Review the vehicle repair history for items related to the current condition.
Inspect the vehicle for any aftermarket accessories that may have been installed incorrectly.
Check for any related technical service bulletins (TSBs) and, if any apply, follow the recommended procedure.
Select the appropriate response from the list below:
A technical service bulletin (TSB) repaired the condition.
- Test complete.
A DTC is present, no TSBs apply, or the TSB did not repair the condition.
- Go to 2
2. DTC IS ACTIVE
NOTE: Allow the vehicle to cool to ambient temperature before continuing with this procedure.
NOTE: A loose gas cap may have caused this DTC to set. Make sure gas cap is tight and in good condition. Make sure the gas cap meets OEM specifications.
Ignition on, engine not running.
With a scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
- Go to 3
No
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.Intermittent Condition
3. EVAPORATIVE SYSTEM INSPECTION
Perform an inspection of the entire evaporative emission system.
Check for the follow conditions:
- Holes or cracks
- Loose seal points
- Evidence of damaged components
- Incorrect routing of hoses and tubes
- Loose or missing Fuel Filler Cap
- Improper installation of the Fuel Fill Cap
- Damaged Locking tabs on Cap and/or fill tube
- Damaged seal points on Cap and/or fill tube
- Fuel cap gasket seal
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test
No
- Go to 4
4. EVAPORATIVE SYSTEM LEAKING
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, vehicles 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.
Is the indicator ball above the red flag?
Yes
- Go to 5
No
- Refer to the Freeze Frame data recorded in step 1. If the data indicates that the vehicle was in motion when the DTC was set, verify that all hoses are properly connected.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test
5. 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 aid diagnosis also.
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.
NOTE: 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 Charts 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 Orifice.
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.
Select the appropriate response from the list below:
A leak was found at the gas cap or fuel filler tube
- Go To 6
A leak was found in one or more of the EVAP System zones
- If the leak is at a hose connection, remove the hose then reconnect the hose and check for a leak again. All other leaks repair as necessary.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test
No leaks were detected
- Go to 7
6. 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.
NOTE: The gas cap adapter is being used as a known good cap.
Was a leak found at the gas cap adapter?
Yes
- Replace the Fuel Filler tube assembly.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test
No
- Replace the gas cap.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test
7. EVAP PURGE SOLENOID
NOTE: After disconnecting the EVAP Purge Solenoid vacuum connections, inspect the lines and solenoid for any signs of contamination from the EVAP Canister. Replace/repair as necessary.
Turn the ignition off.
Disconnect the Evap Purge Solenoid Vacuum hose at the Throttle Body.
NOTE: You are disconnecting the vacuum line at the Throttle Body so you are not disturbing the vacuum connection 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 Evap Purge Solenoid Vacuum hose at the Throttle Body. 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.
Is smoke visible from the EVAP Purge Solenoid if using the EELD, or not hold a vacuum?
Yes
- Replace the EVAP Purge Solenoid.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test
No
- Replace the NVLD Assembly.
- Perform the PCM Verification Test Ver. 1.Powertrain Verification Test