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post #1 of 2 (permalink) Old 12-21-2013, 07:41 AM Thread Starter
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2007 EVAP Problem Next Steps

'07 2.2L Cobalt w/89,000miles. Daughter home from school and when she went there it had set one code PO449 on the 600 mile trip immediately after one fuel fill up. Had her friend replace vent solenoid and pressure sensor on canister as well as solenoid under hood and gas cap. Had codes erased as well. Current codes are PO449, P2431, P2432 (I know these last two are for sec injection and different). I just checked the codes here at home and replaced both evap and exh fuses - both good. Scanner shows about -8inches H2O evap Vapor pressure and even with cap off - something does not seem right here - plugged? also nothing changes when purge signal initiates either. My next steps are to go under car and check voltage at sensors as soon as garage warms up. Will pull both canister solenoid and pressure sensor to verify clean and no debris in them. Will also blow lines from front to back once front solenoid disconnected.

Anyone have other suggestions for next steps? Appreciate any help. Have not erased any codes yet until done with diagnosis. Thanks.
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post #2 of 2 (permalink) Old 12-21-2013, 12:01 PM
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DTC P0449

Circuit Description
A battery voltage is supplied to the evaporative emission (EVAP) canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister vent solenoid valve.

Control Module Command
EVAP Canister Vent Solenoid Valve Position



DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit

Conditions for Running the DTC
• The ignition is ON.

• The system voltage is between 6-18 volts.

• DTC P0449 runs continuously once the above conditions are met.

Conditions for Setting the DTC
• The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.

• The above conditions are present for a minimum of 12 seconds.

Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

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