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Check engine light - Code PO442

This is a discussion on Check engine light - Code PO442 within the Technical / Maintenance forums, part of the General Discussion category; Just received a code PO442 on my '99 Burban. DEFINITION: EVAP small leak/no flow condition. EXPLANATION: The evap sstem is ...

  1. #1
    Registered User crushor's Avatar
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    Check engine light - Code PO442


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    Just received a code PO442 on my '99 Burban. DEFINITION: EVAP small leak/no flow condition. EXPLANATION: The evap sstem is monitored for its ability to hold vacuum. PROBABLE CAUSE: Defective or loose fuel cap ???? EVAP canister or hose cracked or not connected. Purge or vent solenoid defective. Vacuum leak at engine.

    Alright, has anyone had this fault. I question the fuel cap thought...also I was trying to remember if there was a method of finding a leak in a mess of vacuum lines. Not sure this is the same topic, but was thinking propane would create an increase in engine rpm in the area of the bad vacuum line.

    Any assistance is appreciated. Of course, it is now sitting at an airport, waiting for my return, but at lease I will have a point to start when I get home.

    Thanks guys.
    '99 Chevy Burban, 2003 100th Anniversary Harley-Davidson F150 (Bad Fast) , 2006 Mustang GT, 1988 Ford TBird 5.0L, 1947 Willy's CJ-2A, 1996 Ranger, 2012 Sure-Trac 18' Car Hauler, (Soon to be adding modded 1987 Mustang 5.0L to the collection).

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    Supporting Member 1997chevydriver's Avatar
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    Re: Check engine light - Code PO442

    my first place to start is fuel cap. my moms blazer has this code that comes and goes depending on if the fuel cap is tight enough or not
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Re: Check engine light - Code PO442

    I would agree the first place to start is making sure the fuel cap clicks.
    Also you can reset your codes by pulling the ECM fuse (think there is actually 2 of them) but it will reset the computer while keeping your radio settings. Or you can disconnet the battery for 10 min.
    Other then that I believe there is a vent or valve by the tank that there has been issues with. May be the newer trucks though too.


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    Registered User crushor's Avatar
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    Re: Check engine light - Code PO442

    I appreciate the info guys. Per the fuel cap, I have already checked that, to ensure that there is no play, and it did click 3 or 4 times once I reinstalled it. I may try the battery disconnect, but I am still interested in the thought of a vacuum leak. It may not be the case, however, half-zeimers is not allowing me to remember the quick check on that. I will again look at the cap...maybe there is a seal on cap that is leaking by...
    '99 Chevy Burban, 2003 100th Anniversary Harley-Davidson F150 (Bad Fast) , 2006 Mustang GT, 1988 Ford TBird 5.0L, 1947 Willy's CJ-2A, 1996 Ranger, 2012 Sure-Trac 18' Car Hauler, (Soon to be adding modded 1987 Mustang 5.0L to the collection).

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    0_o o_0 0_o o_0 98GreenMachine's Avatar
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    Re: Check engine light - Code PO442

    DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected



    Circuit Description

    The evaporative system includes the following components:

    The fuel tank.
    The EVAP vent solenoid.
    The fuel tank pressure sensor.
    The fuel pipes and hoses.
    The vapor lines.
    The fuel cap.
    The evaporative emission canister.
    The purge lines.
    The EVAP purge solenoid.

    The evaporative leak detection diagnostic strategy is based on applying a vacuum to the EVAP system and monitoring the vacuum decay. The VCM monitors vacuum level via the fuel tank vacuum sensor input. At an appropriate time, the EVAP purge solenoid and the EVAP vent solenoid are turned ON, allowing the engine vacuum to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge solenoid turns OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period. A small leak in the system will cause DTC P0442 to be set.

    Conditions for Running the DTC

    No active MAP sensor DTCs.
    No active TP sensor DTCs.
    No active VS DTCs.
    No active O2 sensor DTCs.
    No active ECT sensor DTCs.
    No active IAT sensor DTCs.
    DTC P0125 not active.
    The Fuel Level is greater than 12.5 % and 87 %.
    The ECT is between 4-30C (39-86F).
    The IAT is between 4-30C (39-86F).
    The cold start temperature difference (ECT minus IAT) is less than:
    1.5C (35F)when the IAT is greater than the ECT or
    8C (46F) when the ECT is greater than the IAT.
    The BARO is greater than 72 kpa.
    The change in fuel tank vacuum is less than 0.6 in. of H2O, or the change in fuel level is less than 8 %.
    The throttle position is less than 75 %.
    The vehicle speed is less than 65 mph (104 km/h).
    The fuel tank vacuum level remains above a calibrated value for a specified number of seconds.

    Conditions for Setting the DTC

    The EVAP system is unable to hold a specified vacuum level for a calibrated number of seconds.

    Action Taken When the DTC Sets

    The VCM illuminates the MIL during the second key cycle in which the DTC sets.
    The VCM stores the conditions which were present when the DTC sets as the Freeze Frame and the Fail Records data.

    Conditions for Clearing the MIL or DTC

    The MIL will turn OFF after one ignition cycle in which the diagnostic runs without a fault.
    The Freeze Frame information and the history DTC will clear after one ignition cycle in which the diagnostic runs without a fault.
    A scan tool can clear the DTC(s)..

    Diagnostic Aids

    Important: An accurate indication of fuel level is required for the VCM to properly pass or fail this DTC. Always diagnose fuel level sensor DTC's before performing this DTC's diagnostic table. Always check for fuel level sensor DTC's stored in history.

    Check for the following conditions:

    A loose, missing, damaged, or improperly installed fuel cap.
    Missing or damaged O-rings at EVAP canister fuel vapor and purge line fittings.
    A cracked or punctured EVAP canister.
    A damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
    Incorrectly routed or defective EVAP system vacuum and vapor lines.
    A poor connection at the VCM: Inspect the harness connectors for the following conditions:
    Backed out terminals.
    Improper mating.
    Broken locks.
    Improperly formed or damaged terminals.
    A poor terminal to wire connection.
    A damaged harness: Inspect the wiring harness to the EVAP vent solenoid EVAP purge solenoid and the fuel tank pressure sensor for an intermittent open or short circuit.
    A missing or damaged weather-pack on the EVAP Purge Solenoid connector.

    Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.

    Test Description

    Number(s) below refer to the step number(s) on the Diagnostic Table.

    3. Inspect the service port. Make sure that the dust cap and valve core are not loose or damaged (the valve core may have left hand threads). If the service port is suspect of leakage use the following procedure:

    Disconnect the purge line from the EVAP Purge solenoid valve.
    Connect a hand vacuum pump to the service port by placing the hose/adaptor over the unthreaded end portion of the service port.
    Apply vacuum to 5 in. Hg. If the vacuum does not hold replace the service port (may require line replacement).

    4. If the vehicle passes the Service Bay Test then an intermittent leak had occurred. Check the fuel tank cap for a possible loose or leaking condition that may have caused this DTC to set.

    If the Service Bay Test can not be run, proceed to Step 5. If a fault is not currently present the diagnostic table steps will return you to Step 3.

    9. Refer to the information supplied with the EVAP pressure/purge diagnostic cart on proper setup and adjustment procedures.

    13. An EVAP Pressure sensor that does not correctly respond to pressure or vacuum will cause this DTC to set.

    The EVAP Pressure Sensor monitors a range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).




    Last edited by 98GreenMachine; 08-19-2011 at 08:54 AM.
    Red4wdKon likes this.
    08 HHR LS - 2.2 | 5 speed | 30 MPG

    98 K1500 Z71 - 204k | L31 | 60E | 3.73's | 3" BL | 33x12.5x15 Dick Cepek F-C II's | Dynomax Ultra Flo X DI/DO | 14 MPG

    84 S15 Jimmy 2dr 4x4 - engine/tranny all rebuilt

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    Registered User crushor's Avatar
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    Re: Check engine light - Code PO442

    Greenmachine...without a doubt, thanks for the info. Very much appreciated.
    '99 Chevy Burban, 2003 100th Anniversary Harley-Davidson F150 (Bad Fast) , 2006 Mustang GT, 1988 Ford TBird 5.0L, 1947 Willy's CJ-2A, 1996 Ranger, 2012 Sure-Trac 18' Car Hauler, (Soon to be adding modded 1987 Mustang 5.0L to the collection).

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    0_o o_0 0_o o_0 98GreenMachine's Avatar
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    Re: Check engine light - Code PO442

    Not a problem :)
    08 HHR LS - 2.2 | 5 speed | 30 MPG

    98 K1500 Z71 - 204k | L31 | 60E | 3.73's | 3" BL | 33x12.5x15 Dick Cepek F-C II's | Dynomax Ultra Flo X DI/DO | 14 MPG

    84 S15 Jimmy 2dr 4x4 - engine/tranny all rebuilt

 

 

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