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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 DTS 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P0449

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

Battery Positive - Vent Supply

P0449

P0449

P0449

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EVAP Vent Solenoid Control

P0449

P0449

P0449

P0449

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Circuit/System Description

Battery voltage is supplied to the 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.

Conditions for Running the DTC
    • The ignition is ON.
    • The system voltage is between 9-18 volts.
    • DTC  P0449 runs continuously when 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 for a minimum of 12 seconds.

Action Taken When the DTC Sets
    • DTC P0449 is a Type B DTC.
    • 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
    • DTC P0449 is a Type B 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.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Troubleshooting with a Test Lamp
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Output Controls

Circuit/System Verification
  1. With the ignition ON and the engine OFF, command the EVAP vent solenoid ON and OFF with a scan tool.
  2. Listen or feel for a click when the valve operates. Verify that both the ON and the OFF states are commanded.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the EVAP canister vent solenoid valve.
  2. Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.
    3. ⇒If a test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the voltage supply circuit fuse is open, test or replace the EVAP canister vent solenoid valve.
  3. Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.
  4. Command the solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between commanded states.
    5. ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the control module.
    ⇒If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the control module.
  5. If all circuits test normal, replace the EVAP canister vent solenoid valve.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Evaporative Emission Canister Vent Solenoid Valve Replacement
    •  Control Module References for engine control module (ECM) replacement, setup, and programming