2010 Cadillac CTS Sedan AWD V6-3.6L Page 1413
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
With the engine running, the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 %, the fuel
tank vacuum should not increase to more than -15 mmHg (-8 inches H2O).
P0449
DTC P0449, P0498, or P0499 (w/LLT)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0449
- Evaporative Emission (EVAP) Vent Solenoid Control Circuit
DTC P0498
- Evaporative Emission (EVAP) Vent Solenoid Valve Control Circuit Low Voltage
DTC P0499
- Evaporative Emission (EVAP) Vent Solenoid Valve Control Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The evaporative emission (EVAP) canister vent valve is used for EVAP system diagnostics. The EVAP canister vent valve is a normally open
valve. Battery positive voltage is supplied directly to the EVAP canister vent valve. The engine control module (ECM) controls the solenoid by
grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage.
The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM
detects the control circuit voltage is within a predetermined range when the circuit is commanded OFF, this DTC sets.
Conditions for Running the DTC
* The engine speed is greater than 80 RPM.
* The ignition voltage is between 10-18 volts.
* The ECM has commanded the EVAP canister vent valve ON and OFF at least once during the ignition cycle.
* The DTCs runs continuously once the above conditions are met.
Conditions for Setting the DTC
P0449
The ECM detects the voltage on the EVAP canister vent valve control circuit is between 2.6-4.6 volts when the driver is commanded OFF. The
condition exists for less than 4 seconds or for a cumulative of 30 seconds.
P0498
The ECM detects the voltage on the EVAP canister vent valve control circuit is less than 2.6 volts when the driver is commanded OFF. The
condition is present for greater than 4 seconds or for a cumulative of 30 seconds.
P0499
The ECM detects the voltage on the EVAP canister vent valve control circuit is greater than 4.6 volts when the driver is commanded ON. The
condition is present for greater than 4 seconds or for a cumulative of 30 seconds.
