For 1990-2009 cars

### Purpose

#### EVAP Control System Overview

(1) | EAVP Vent Valve/Solenoid
(2) | EVAP Vent Valve/Solenoid Ignition Feed Circuit Terminal
(3) | EVAP Vent Valve/Solenoid Control Circuit Terminal
(4) | EVAP Vent Valve/Solenoid Filter
(5) | EVAP Vapor Lines
(6) | Fuel Tank Pressure Sensor
(7) | Fuel Tank Pressure Sensor Ground Circuit Terminal
(8) | Fuel Tank Pressure Sensor Signal Circuit Terminal
(9) | Fuel Tank Pressure Sensor Circuit 5 Volt Reference Circuit Terminal
(10) | Fuel Filler Pipe
(11) | Modular Fuel Sender Assembly
(12) | Fuel Limiter Vent Valve (FLVV)
(13) | Pressure/Vacuum Relief Valve (Optional)
(14) | EVAP Canister
(15) | EVAP Canister Purge Valve/Solenoid Ignition Feed Circuit Terminal
(16) | EVAP Canister Purge Valve/Solenoid Control Circuit Terminal
(17) | Intake Manifold Vacuum Source
(18) | EVAP Canister Purge Valve/Solenoid
(19) | EVAP Service Port

The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.

When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor.

The system is required in order to detect the evaporative fuel system leaks as small as 0.040 between the fuel filler cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank in order to create a small vacuum.

### Circuit Description

The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.

When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor.

The system is required in order to detect the evaporative fuel system leaks as small as 0.040 between the fuel filler cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank in order to create a small vacuum.

The evaporative system includes the following components:

• | The fuel tank.

• | The EVAP vent valve/solenoid.

• | The fuel tank pressure sensor.

• | The fuel pipes and hoses.

• | The fuel fill cap.

• | The EVAP vapor lines.

• | The EVAP purge lines.

• | The EVAP canister.

• | The EVAP canister purge valve/solenoid.

The POWERTRAIN CONTROL MODULE (PCM) supplies a ground to energize the valve (purge on). The EVAP canister purge valve control is Pulse Width Modulated (PWM) or turned on and off several times a second. The duty cycle (pulse width) is determined by engine operating conditions including load, throttle position, coolant temperature and ambient temperature. The duty cycle is calculated by the PCM and the output is commanded when the appropriate conditions have been met. The system checks for conditions that cause the EVAP system to purge continuously by commanding the EVAP canister vent valve on and the EVAP purge valve off (EVAP canister vent valve CLOSED, EVAP purge PWM 0%). If vacuum level in the fuel tank increases during the test, a continuous purge flow condition is indicated. This can be caused by any of the following conditions:

• | EVAP purge valve leaking internally.

• | EVAP purge and engine vacuum lines switched at the EVAP purge valve.

• | EVAP purge valve control circuit grounded.

If any of these conditions are present, DTC P1441 will set.

### Conditions for Running the DTC

• | No ECT, Map, TP MAF sensor, VSS, HO2S, Misfire, Fuel Trim, Injector circuit, EGR Pintle Position DTCs set.

• | All conditions for DTC P0440, P0442 and P0446 diagnodtic tests have been met and passed.

• | Startup engine coolant temperature is not more than 8°C (14°F) greater than startup intake air temperature.

• | Startup intake air temperature is between 4°C and 30°C (40° F and 86° F).

• | Startup air temperature not more than 2°C (4° F) greater than start-up engine coolant temperature.

• | Fuel tank fuel level is between 15% and 85%.

• | BARO is greater than 75 kPa.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.

• | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using a scan tool.

### Conditions for Setting the DTC

A continuous open purge flow condition is detected during the diagnostic test (fuel tank pressure decreases to less than -11 in. H2O).

### Diagnostic Aids

Check for the following conditions:

• | Poor connection at the PCM.

| Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

• | Damaged harness.

| Inspect the wiring harness for damage.

• | If the harness appears to be OK, connect the

(1) | Main Valve
(2) | Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3) | Nitrogen Cylinder
(4) | Black Connecting Hose
(5) | Threaded Fitting
(6) | Gauge Set

EVAP pressure/purge diagnostic station to the EVAP service port, pressurize the EVAP system to 10 in. H2O and observe the Fuel Tank Pressure display on the scan tool while moving connectors and wiring harnesses related to the EVAP purge valve. A sudden change in the display will indicate the location of the malfunction.

• | Incorrect vacuum line routing.

| Verify that the source vacuum line routing to the EVAP purge valve is correct and that the EVAP purge and source vacuum lines to the EVAP purge solenoid are not switched.

• | Malfunctioning or damaged canister.

1. | Turn off the ignition switch.

2. | Remove the EVAP purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

3. | Lightly tap the EVAP purge valve and (if applicable) the vacuum switch on a clean work area looking for carbon particles exiting either of the vacuum ports.

4. | If no carbon release is evident, reinstall the components and continue with the DTC P1441 table. If carbon is being released from either component, continue with this service procedure.

5. | Remove the charcoal canister from the vehicle.

6. | Ensure that the main cylinder valve is turned off on the

(1) | Main Valve
(2) | Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3) | Nitrogen Cylinder
(4) | Black Connecting Hose
(5) | Threaded Fitting
(6) | Gauge Set

EVAP purge/pressure diagnostic station.

7. | Disconnect the black hose that connects the nitrogen cylinder to the EVAP purge/pressure diagnostic station at the pressure regulator by unscrewing the knurled nut on the regulator. No tools are required to remove the black hose from the regulator.

8. | Using a section of vacuum line, connect one end over the open threaded fitting of the EVAP purge/pressure diagnostic station pressure regulator.

9. | Connect the remaining end to the EVAP purge valve end of the EVAP purge line at the vehicle and turn on the main nitrogen cylinder valve. Continue to blow any debris from the purge line for 15 seconds.

10. | Return the EVAP Pressure/Purge Diagnostic Station to its original condition by re-installing the black hose that was disconnected in step 7.

11. | Replace the following components:

• | The EVAP purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

• | The EVAP canister. Refer to Evaporative Emission Canister Replacement .

12. | Proceed with the DTC P1441 diagnostic table.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

1. If an EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction will very likely correct the condition that set DTC P1441.

2. Checks the Fuel Tank Pressure sensor stuck high condition. The scan tool should read within 1.0 in H2O of the specified value.

3. Checks for a stuck open EVAP purge valve.

4. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.

5. If the EVAP purge and engine vacuum lines are switched at the EVAP purge solenoid, the solenoid valve will leak vacuum.

6. The PCM will command the EVAP purge and EVAP canister vent valves closed with the scan tool Seal System EVAP output control function activated. Fuel tank pressure should not decrease under this condition.

#### DTC P1441 - Enhanced EVAP System Flow During Non-Purge

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain OBD System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Important: Visually/Physically inspect for the following conditions:

• | Vacuum or purge lines disconnected. Refer to Emission Hose Routing Diagram .

• | Loose or missing fuel fill cap.

Is DTC P1665 Evaporative Emission (EVAP) Vent Solenoid Control Circuit or DTC P1676 Evaporative Emission (EVAP) Purge Solenoid Control Circuit also set?

--

Go to other DTC(s) First

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Remove the fuel cap.
3. Turn ON the ignition, with the engine OFF.
4. Observe Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure at the specified value?

0 in. H2O

Go to Step 4

Go to Step 11

4 | Important: : Before continuing with diagnosis, zero the EVAP Pressure and Vacuum (inches of H2O) gauges on the

(1) | Main Valve
(2) | Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3) | Nitrogen Cylinder
(4) | Black Connecting Hose
(5) | Threaded Fitting
(6) | Gauge Set

EVAP pressure/purge diagnostic station (refer to tool operating instructions).

Important: Do not exceed the pressure in the specified value.

1. Ignition switch OFF.
2. Reinstall the fuel fill cap.
3. Connect the EVAP pressure/purge diagnostic station to the EVAP service port.
4. Capture Fail Record data for DTC P1441 and clear DTCs.
5. Using the scan tool, EVAP Purge/Seal, select seal option to seal the EVAP system.
6. Attempt to pressurize the system to the specified value by slowly turning the EVAP station rotary switch to the "Pressure" position. (monitor pressure using the EVAP pressure gauge on the cart with the rotary switch in the "OFF/Hold" position).

Can the specified value be achieved?

5 in. H2O

Go to Step 5

Go to Step 6

5 |

1. Maintain tank pressure at the specified value. Monitor pressure using the EVAP pressure gauge on the cart with the rotary switch in the "OFF/Hold" position.
2. Observe Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure at the specified value?

5 in. H2O

Go to Diagnostic Aids

Go to Step 10

6 | Check the EVAP purge and source vacuum line routing and connections at the EVAP purge valve. Refer to Emission Hose Routing Diagram . Are the EVAP purge and source vacuum lines connected correctly at the EVAP purge valve? | -- | Go to Step 7 | Go to Step 9
7 |

1. Connect the in. Hg vacuum gauge on the EVAP service station to the purge valve/solenoid, canister side.
2. Turn ON the ignition, with the engine OFF.
3. Using the scan tool, EVAP Purge/Seal, select the seal option to seal the EVAP system.
4. Start the engine and idle.
5. Run the engine from 1200-1500 RPM and observe vacuum level.

Is vacuum level near the specified value?

0 in. Hg

Go to Diagnostic Aids

Go to Step 8

8 | Important: : Check for carbon release into the EVAP system. Refer to Diagnostic Aids. Replace the EVAP canister purge valve/solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 12 | --
9 |

- Correct the EVAP purge and source vacuum line routing and connections.

Is the action complete?

--

Go to Step 12

--

10 |

1. Visually/Physically check for the following conditions:

• | Restricted fuel tank vapor line.

• | Restricted EVAP purge line.

2. If a problem is found repair as necessary.

Was a problem found?

--

Go to Step 12

Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

11 |

1. Check for a kinked or restricted canister purge line between the EVAP canister purge valve and EVAP canister.
2. Repair the EVAP canister purge line as necessary.

Is action complete?

0 in H2O

Go to Step 12

Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

12 |

1. Reconnect all EVAP hardware that was previously disconnected.
2. Ignition switch ON, Engine OFF.
3. Using the scan tool, Purge/Seal, select the seal option to seal the EVAP system.
4. Pressurize the system to the first greater specified value by slowly turning the EVAP service station rotary switch to the "pressure" position. Monitor the pressure with the gauge on the cart with switch in the "OFF/Hold" position.

Does the EVAP pressure decrease to less than the second lower specified value within 3 minutes with the rotary switch in the "OFF/Hold" position?

15 in. H2O

10 in H2O

Go to Step 3

System OK