For 1990-2009 cars

### 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 P0496 : Evaporative Emissions (EVAP) System Continuous Purge Flow

### Circuit Description

This DTC tests for continuous intake manifold vacuum flow to the Evaporative Emission (EVAP) System. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Closed. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is greater than a predetermined value within a predetermined time, this DTC sets.

FTP Sensor Signal Voltage | Fuel Tank Pressure
--- | ---
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum
Low, Approximately 1.5 Volts or Less | Positive Pressure

### Conditions for Running the DTC

• | DTCs P0031, P0032, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0313, P0335, P0336, P0402, P0404, P0405, P0406, P0443, P0452, P0453, P0462, P0463, P0488, P0502, P0506, P0507, P0562, P0563, P1166, P2195, P2196, and P2297 are not set.

• | One of the following conditions is met:

- | The ignition is off for greater than 12 hours.

- | OR

- | The start-up intake air temperature (IAT) and the start-up engine coolant temperature (ECT) are within 8°C (46°F).

• | The ignition 1 voltage is between 11-16 volts.

• | The barometric pressure (BARO) is greater than 72 kPa.

• | The start-up ECT and start-up IAT are between 4-34°C (39-93°F).

• | The start-up IAT is 3°C (37°F) less than the actual IAT.

• | The purge enable time is less than pre-determined value based on startup ECT.

• | The fuel level is between 6-93 percent.

• | The engine run time is between 1-360 seconds plus purge enable time.

• | The DTC run once an ignition cycle when the above conditions are met.

### Conditions for Setting the DTC

The FTP sensor indicates vacuum during a non-purge condition.

### Action Taken When the DTC Sets

DTC P0496 is a Type A/B DTC.

### Conditions for Clearing the DTC

DTC P0496 is a Type A/B DTC.

### Diagnostic Aids

• | Observe the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.

• | The EVAP system tests run when engine is first started and meets the Conditions for Running the DTC. An intermittent condition could be caused by an improperly installed or damaged EVAP canister purge solenoid valve , or by a temporary blockage or restriction in the EVAP canister purge solenoid valve.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Description and Operation

Evaporative Emission Control System Description

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

#### With Service Bay Test

1. Verify the EVAP system using the EVAP Service Bay Test. DTC P0496 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

#### Without Service Bay Test

1. Ignition On, observe the DTC information with a scan tool. DTC P0496 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Remove the fuel fill cap. Observe with a scan tool the FTP sensor pressure parameter. Verify the scan tool FTP sensor pressure parameter is 0 inches H2O.

⇒ | If less than the specified value replace the FTP sensor.

2. Install the fuel fill cap.
3. Engine idling command the EVAP vent closed. Increase the engine speed to 1,200-1,500 RPM. Observe with a scan tool the FTP sensor pressure parameter.
4. Verify the scan tool FTP sensor pressure parameter is 0 H2O.

⇒ | If less than the specified value replace the Evaporative Emission Canister Purge Solenoid Valve.

### Repair Instructions

• | Fuel Tank Pressure Sensor Replacement

• | Evaporative Emission Canister Purge Solenoid Valve Replacement

### Repair Verification

#### With Service Bay Test

Verify the EVAP system using the EVAP Service Bay Test. DTC P0496 should not set.

#### Without Service Bay Test

1. Engine idling command the EVAP vent closed.
2. Increase the engine idle to 1,200-1,500 RPM.
3. Observe with a scan tool the FTP sensor pressure parameter.
4. Verify the scan tool FTP sensor pressure parameter is 0 H2O.
5. Clear the DTCs with a scan tool.