I recently had the check engine light come on on my 2003 Silverado and it is for Code 442 which relates to the Evap System. The mechanic indicated that the cannister vent valve needs to be replaced for $450. based on what I am reading, the valve may not not replacing?
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Re: GM Code 442
Do you mean code P0442? I would assume that's what you mean since you said it relates to the Evap System
This code indicates that there is a fuel vapor leak in the system. This means that a very small leak has been detected. The leak can be from a hole as small as 1mm
This code point towards any of the following: a loose gas cap or a non factory spec gas cap a small leak or hole in the fuel vapor hose/tube faulty vent o-ring seal
The most common fixes is to re install the gas cap, clear the codes, and see if the code returns. Or replace the gas cap and clear the codes and see if it returns. Finally inspect the hoses/tubes for cuts/holes
This code in no way points to a canister requiring to be replaced.
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code p 0106 refers to manifold absolute pressure(MAP) sensor / barometric pressure (BARO) sensor---range /performance problem===causes --intake exhaust leak---wiring---MAP sensor---BARO sensor
code p 442 refers to evaporative emission(EVAP) system--small leak detected===causes --hose connections ---intake leak---EVAP cannister purge valve
it also refers to EVAP system ---large leak detected ---cap loose/ off ===causes --mechanical fault , hose connection EVAP pressure sensor
code p 0455 refers to EVAP system --large leak detected ===causes same as for p 0442 causes
The PO 442 code is an EVAP system small leak, either in the evaporative system or cooling. Sometimes this will occur after a drenching rain and remain until the diagnosis code is reset, usually will disappear after you read the codes. If not, a dealer can reset the code system via the radio believe it or not. PO 445 is similar, an EVAP system code but is usually related to gas vapors being sent to the engine rather than through the atmospheric venting system. Check the gas cap system here first, a gas cap not properly tightened (3 click) will sometimes cause this. Also, look to the spark system wiring harness or purge control solenoid.
Code 442 is a common code for a small leak in the EVAP system. The computer vents the gas tank to the vapor canister when the engine is running. The computer checks for leaks also. The EVAP system would need to be checked for leaks.
NOPE CANT ERASE CODES UNTIL THE PROBLEM IS FIXED OR THE SERVICE ENGINE LIGHT SOON WILL STAY ON. CODE PO441 - EVAPORATIVE EMISSION EVAP SYSTEM INCORRECT FLOW DETECTED.CHECK INTAKE VACUUM HOSE CONNECTIONS AT THE EVAP CANISTER PURGE VALVE.IF ALL IS GOOD.THE EVAP CANISTER PURGE VALVE COULD BE BAD. CODE PO 442 - EVAPORATIVE EMISSION EVAP SYSTEM SMALL LEAK DETECTED. EVAPORATIVE EMISSION SYSTEM LARGE LEAK DETECTED FUEL CAP LOOSE OR OFF MISSING. CODE PO 446 - EVAPORATIVE EMISSION EVAP SYSTEM VENT CONTROL CIRCUIT MALFUNCTION.
Code P0442 relates to the Evaporative Emmission Control (EVAP) system and denotes a small leak.
The EVAP system prevents the escape of dangerous fuel vapours - these vapours are re-directed to what's called a Charcoal Canister (looks like a medium-sized cylinder with tiny hoses running to it).
As this relates to fuel vapours, one of the most common causes can be as simple as the petrol cap is not screwed on tight enough (or has been recently replaced with an incorrect aftermarket type). Other causes can be a hose has come off somewhere, a hose has a pin-hole or is perforated.
This type of code will usually itself after a few trips, but most people prefer to clear codes after resolving the cause.
First, check the petrol cap.
Second, you will need to trace all hoses within the Evap system and check for any signs of leakage (wear or damage etc), and remedy accordingly.
Codes can be cleared either by using a suitable Diagnostic Scan Tool, or simply disconnecting the NEGATIVE lead of your car battery for a few minutes, then reconnecting (Note: if the battery is disconnected or goes flat, run engine after power is restored, to allow the engine to relearn its settings).
If the code returns, then you should have the Evap system checked properly by an authorised dealership.
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DTC P0446 Evaporative Emission (EVAP) Vent System Performance
The vehicle control module (VCM) monitors the performance of the evaporative
emission (EVAP) system by applying a predetermined level of vacuum to the
EVAP system and monitors the vacuum decay rate. The VCM sets this diagnostic
trouble code (DTC) if the vacuum decay rate is more than a predetermined
value. The VCM monitors the amount of vacuum and the amount of pressure
in the EVAP system by monitoring the fuel tank pressure sensor. For
this DTC, the VCM turns ON both the EVAP purge valve and the EVAP vent
valve when the Conditions for Running the DTC are met. This applies
an engine vacuum to a closed EVAP system. The VCM turns OFF both the
EVAP purge valve and the EVAP vent valve when the system reaches a correct
amount of vacuum. The EVAP system should quickly RELEASE the vacuum
in the EVAP system with the EVAP purge valve OFF and the EVAP vent valve
OFF (open). This test indicates a blocked or restricted EVAP vent path
if the EVAP system fails to release the vacuum quickly enough.