Dodge Ram Truck 1500-2500-3500. Manual - part 896

P0457-LOOSE FUEL CAP (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS).

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

Fuel level is recorded when the ignition key is turned off and is compared to the fuel level when the ignition key is
turned back on. The PCM recognizes an increase in fuel level and will fail the Medium leak test because the fuel
cap is broken or not installed properly. GAS CAP will be displayed in odometer to inform the owner that the cap is
off of loose.

•

When Monitored:
Engine running. 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 sys-
tem. 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

NVLD SWITCH

EVAP PURGE SOLENOID

EVAP PURGE SYSTEM MEDIUM LEAK

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING) .

Diagnostic Test

ACTIVE DTC

NOTE: After the PCM has determined the leak test inconclusive and sees an increase in fuel level, the PCM
will request the GAS CAP indicator on to inform the customer that the gas fill cap is loose or off.
Ignition on, engine not running.

With a scan tool, read DTCs.

Is the DTC active at this time?

Yes

>> Go To 2

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

LOOSE OR MISSING FUEL FILL CAP

Inspect the fuel fill cap.

Inspect the cap for any abnormal defects.

Was the cap off, missing, or broken?

Yes

>> Properly install the fuel fill cap and proceed to step 3.

>> Go To 4

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ENGINE - ELECTRICAL DIAGNOSTICS - 3.7L/4.7L/5.7L

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P0457-LOOSE FUEL CAP (CONTINUED)

NVLD SERVICE TEST

With the scan tool perform the NVLD Service Test.

Does the NVLD Service Test pass?

Yes

>> Test complete.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

>> Go To 4

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 neg-
ative 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 Medium 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.

Is the indicator ball above the red flag?

Yes

>> Go To 5

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

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P0457-LOOSE FUEL CAP (CONTINUED)

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.

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 ultra-
violet (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: 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.

Was a leak found?

Yes

>> Repair or replace the leaking component as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

>> Go To 6

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.

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.

Does the EVAP Purge Solenoid hold vacuum?

Yes

>> Go To 7.

>> Replace the Evap Purge Solenoid.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

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P0457-LOOSE FUEL CAP (CONTINUED)

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.

Did the NVLD Switch operate as described above?

Yes

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS

AND TESTING)

>> Replace the NVLD Assembly.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

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