For 1990-2009 cars

Refer to Engine Controls schematics

#### EVAP Controls,and IAC Valve

Engine Controls Components
Idle Up signals
VSS Output
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Cell 10: Ignition Switch, IGN Fuse, and ST Fuse
Cell 10: Alt-S, AM2, Dome, EFI, Hazard, Horn, and Main Fuses
Cell 14: SP254 and SP261
Cell 14: SP254 and SP261
Cell 14: Battery, G100, G101, G102, G103, and G104
and

#### Fuel Supply System

Engine Controls Components
Fuel Injectors
Tachometer
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Cell 14: SP254 and SP261
Cell 14: SP254 and SP261
Cell 14: Battery, G100, G101, G102, G103, and G104
Cell 10: Ignition Switch, IGN Fuse, and ST Fuse
Cell 10: Alt-S, AM2, Dome, EFI, Hazard, Horn, and Main Fuses
.

### Circuit Description

The powertrain control module (PCM) monitors the positive or negative pressure in the fuel tank using the fuel tank pressure sensor. Under certain engine operating conditions, the PCM turns ON the EVAP pressure switching solenoid in order to monitor control pressure in the EVAP system. The PCM is able to detect any abnormal conditions by the fluctuation of this pressure. The diagnostics performed by the fuel tank pressure sensor can warn the driver of a malfunction in the EVAP system by illuminating the MIL. The EVAP control system prevents the emission of the fuel vapors. The fuel vapor generated in the fuel tank while driving or idling enters the EVAP canister where a charcoal element absorbs and stores the fuel vapor. The EVAP canister is purged by the PCM-controlled EVAP canister purge solenoid valve. The EVAP canister purge valve releases the fuel vapors into the intake manifold to be burned in the combustion process.

### Conditions for Setting the DTC

• | The EVAP canister vent valve is OFF.

• | The pressure at the fuel tank pressure sensor is not within the expected values.

OR:

• | The EVAP pressure switching solenoid is OFF.

• | The pressure at the fuel tank pressure sensor is not within the expected values.

OR:

The pressure indicated in the EVAP canister is equal to atmospheric pressure after the EVAP canister purge valve is turned OFF.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.

• | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.

• | A DTC can be cleared by using the scan tool Clear Information function.

### Diagnostic Aids

• | If DTC P0446 is the only EVAP DTC set, the most likely cause is an inoperable EVAP pressure switching solenoid. Inspect the EVAP pressure switching solenoid carefully for faulty connections and erratic operation.

• | DTC P0446 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating a DTC P0446.

• | An intermittent DTC P0446 can be caused by a faulty EVAP canister. An EVAP canister that has released carbon particles can cause the EVAP canister purge valve to fail and leak intermittently. Inspect the EVAP purge system for carbon contamination before returning the vehicle to service. Refer to Evaporative Emission System Cleaning .

• | For functional checks of the components listed above, refer to Evaporative Emission Control System Diagnosis .

• | An intermittent malfunction may be caused by a fault in any of the EVAP solenoid electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks the EVAP control system components for correct installation or damage. Inspect all lines and hoses. This includes a manufacturer approved gas cap that is correctly installed and tightened.

3. This step checks for the correct function of the EVAP canister purge valve.

4. This step checks the control circuit of the EVAP canister purge valve. Because the control circuit of the EVAP canister purge valve is PWM, the test lamp flickers during illumination, when commanded ON by the scan tool. This is the normal condition, indicating that the PCM and control circuit are OK.

5. This step determines if a fuel tank pressure sensor malfunction is present. The input signal of the fuel tank pressure sensor should indicate atmospheric pressure with the fuel tank filler cap removed. The fuel tank pressure sensor will vary with atmospheric pressure. A typical pressure at sea level is between 0.0-0.99 mm Hg (0.0-0.5 in H2O).

6. This step checks for a possible leak in the EVAP system. The purpose of this inspection is to determine whether 5 to 6 inches of H2O can be obtained and held for at least 2 minutes.

7. This step checks whether there is trapped negative or positive pressure at the FTP sensor.

8. This step checks for leaks in the fuel supply system. By plugging the ORVR vent line and the EVAP vapor line, the fuel tank, the fuel filler hose assembly, and the fuel tank components can be pressurized and checked for leaks. Be sure to check all connections and sealing points for leaks.

9. This step determines if the malfunction that caused the DTC P0446 is still present. Operating the vehicle in Check mode enhances the diagnostic capabilities of the PCM. The EVAP Purge diagnostic can be monitored on the scan tool under the MIL/System Status selection of System Information. When the EVAP Purge test displays a YES status, indicating that the purge system diagnostic is completed, check for DTC P0446 in the Last Test Failed screen of the scan tool. If there is no DTC P0446 displayed the EVAP purge system diagnostic has run and passed, indicating that no malfunction was present this time. The DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that the MIL/System Status tests only indicate that the test has run, not whether the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved. For additional information on check mode operation refer to Powertrain Control Module Diagnosis.

10. The EVAP canister has component parts that cannot be diagnosed or tested on the vehicle. The EVAP canister should be inspected and tested for correct operation by performing the EVAP canister inspection procedures in EVAP Control System Diagnosis.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Install a scan tool and check for DTCs. Is a DTC P0450 present? | -- | Go to DTC P0450 Fuel Tank Pressure Sensor Circuit | Go to Step 3
3 |

1. Visually and physically inspect the EVAP control system for the correct installation and routing of the lines and hoses.

Refer to Evaporative Emission Control System Operation Description for EVAP system hose routing diagrams.

2. Visually and physically inspect all of the following components for cracks, leaks, or damage:

• | The EVAP canister purge valve

• | The fuel tank pressure sensor

• | The EVAP pressure switching solenoid

• | The EVAP canister

• | The EVAP system lines, hoses, and fittings

• | The fuel tank

3. Inspect the fuel tank filler cap for the correct part and the correct installation.
4. Repair any faults found as necessary.

Was repair necessary?

--

Go to Step 48

Go to Step 4

4 |

1. Disconnect both vacuum hoses from the EVAP canister purge valve.
2. Blow air into the lower port of the EVAP canister purge valve.

Air should NOT pass through the solenoid and out the upper port.

3. Turn ON the ignition, with the engine OFF.
4. Using a scan tool command the EVAP canister purge valve ON.
5. Blow air into the lower port of the EVAP canister purge valve. Air should pass through the solenoid and out of the upper port.

Did the EVAP canister purge valve pass both tests?

--

Go to Step 9

Go to Step 5

5 | Measure the resistance of the EVAP canister purge valve with a digital multimeter (DMM). Is the resistance less than the specified range? | 27-33 ohms at 20°C (68°F) | Go to Step 42 | Go to Step 6
6 |

1. Disconnect the electrical connector from the EVAP canister purge valve.
2. Turn ON the ignition, with the engine OFF.
3. Probe the harness side of the ignition positive voltage circuit of the EVAP canister purge valve with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 8

7 |

1. Turn ON the ignition, with the engine OFF.
2. Probe the engine harness side of the control circuit of the EVAP canister purge valve with a test lamp connected to B+.
3. Use the scan tool in order to command the EVAP canister purge valve ON and OFF while observing the test lamp.

Did the test lamp illuminate only when the EVAP canister purge valve was commanded ON?

--

Go to Step 38

Go to Step 45

8 | Repair the open in the ignition positive voltage circuit of the EVAP canister purge valve. Refer Wiring Repairs to in Wiring Systems. Is the action complete? | -- | Go to Step 48 | --
9 |

1. Loosen the fuel tank filler cap in order to release any pressure inside the fuel tank.
2. Turn ON the ignition, with the engine OFF.
3. Observe the fuel tank pressure sensor parameter on the scan tool.

Is the fuel tank pressure sensor within the specified range?

0.0-0.99 mm Hg (0.0-0.5 in H2O)

Go to Step 10

Go to Step 22

10 |

1. Disconnect the electrical connector. from the EVAP canister vent valve
2. Turn ON the ignition, with the engine OFF.
3. Probe the harness side of the ignition positive voltage circuit of the EVAP canister vent valve with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 13

11 |

1. Remove the EVAP canister vent valve from the air cleaner housing.
2. Disconnect the vacuum hose from the EVAP canister vent valve.
3. Blow air into the lower port of the EVAP canister vent valve.

Air should pass through the solenoid and out the upper port.

4. Using a fused jumper wire, supply battery positive voltage to terminal 2 of the EVAP canister vent valve.
5. Connect terminal 1 of the EVAP canister vent valve to ground.
6. Blow air into the lower port of the EVAP canister vent valve. Air should NOT pass through the solenoid and out of the upper port.

Did the EVAP canister vent valve pass both tests?

--

Go to Step 12

Go to Step 39

12 |

1. Turn ON the ignition, with the engine OFF.
2. Probe the engine harness side of the control circuit of the EVAP canister vent valve with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 37

Go to Step 14

13 | Repair the open in the ignition positive voltage circuit of the EVAP canister vent valve. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | --
14 | Measure the resistance of the EVAP canister vent valve with a DMM. Is the resistance within the specified range? | 25-30 ohms at 20°C (68°F) | Go to Step 15 | Go to Step 39
15 |

1. Remove the fuel filler cap and install the J 41415-30 gas cap adapter to the fuel filler pipe.
2. Connect the J 41413 EVAP pressure/purge cart to the gas cap adapter.
3. Pressurize the EVAP system to the specified value with the EVAP pressure/purge cart and switch to HOLD.

Does the EVAP system hold the specified pressure for at least 2 minutes?

8.5-10.5 mm Hg (4.5-5.5 in. H2O)

Go to Step 17

Go to Step 16

16 |

1. Check for a leak in the following components:

• | The EVAP pressure switching solenoid

• | The vacuum hoses connected to the EVAP pressure switching solenoid

2. Repair or replace any components as necessary.

Was a repair necessary?

--

Go to Step 48

Go to Step 30

17 |

1. Disconnect the electrical connector from the EVAP pressure switching solenoid.
2. Turn ON the ignition, with the engine OFF.
3. Probe terminal 2 of the electrical connector on the harness side with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 18

Go to Step 21

18 |

1. Remove the EVAP pressure switching solenoid. Refer to Evaporative Emission Pressure Switching Solenoid Replacement .
2. Check the EVAP pressure switching solenoid with the off-vehicle diagnostic procedures. Refer to Evaporative Emission Control System Diagnosis .

Did the EVAP pressure switching solenoid pass all the tests?

--

Go to Step 19

Go to Step 33

19 |

1. Turn ON the ignition, with the engine OFF.
2. Probe the engine harness side of the control circuit of the EVAP pressure switching solenoid with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 37

Go to Step 20

20 | Refer to Evaporative Emission Control System Operation Description for the EVAP system hose routing diagram used in the following procedure.

1. Remove the ORVR vent line from the EVAP canister and plug the hose. Refer to Evaporative Emission Canister Replacement .
2. Remove the EVAP vapor line and the purge line to the canister purge solenoid from the EVAP canister.
3. Connect the EVAP vapor line and the purge line together using a section of vacuum pipe.
4. Attempt to pressurize the EVAP system to the specified value with the J 41413 EVAP pressure/purge cart and HOLD.
5. Locate any leaks in the EVAP and fuel supply systems using the J 41416 ultrasonic leak detector. If necessary lower the fuel tank in order to check the condition of the fill limiter vent valve and the rollover valve. Be sure to check the fuel sender assembly for a correct seal.

Were any EVAP or fuel supply system leaks found?

56 mm Hg (30 in. H2O)

Go to Step 32

Go to Step 43

21 | Repair the open in the ignition positive voltage circuit of the EVAP pressure switching solenoid. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | --
22 |

1. Disconnect the vapor pressure supply hose to the fuel tank pressure sensor.
2. Turn ON the ignition, with the engine OFF.
3. Observe the fuel tank pressure sensor parameter on the scan tool.

Is the fuel tank pressure sensor within the specified range?

0.0-0.99 mm Hg (0.0-0.5 in H2O)

Go to Step 23

Go to Step 24

23 |

1. Inspect for the cause of the trapped vapor pressure to the FTP sensor. Check for the following conditions:

• | A pinched, crushed, or restricted vapor line or hose from the fuel tank

• | A blocked or restricted vapor pressure passage in the fuel tank

2. Repair as necessary.

Is the action complete?

--

Go to Step 48

--

24 |

1. Turn OFF the ignition.
2. Disconnect the electrical connector from the fuel tank pressure sensor.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the connector cavity 3 on the harness side using a DMM.

Does the voltage equal the specified value?

5.0 V

Go to Step 25

Go to Step 26

25 | Measure the voltage on the harness side of the connector cavity 2 with a DMM. Is the voltage near the specified value? | 4.9 V | Go to Step 28 | Go to Step 27
26 | Repair the open in the reference voltage circuit of the fuel tank pressure sensor between the sensor and SP259. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | --
27 |

1. Check the input circuit of the fuel tank pressure sensor for an open or short.
2. Verify that the input circuit is not shorted to the sensor ground circuit.
3. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 48

Go to Step 47

28 | Probe the sensor connector cavity 1 on the harness side with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 36 | Go to Step 29
29 | Repair the open in the ground circuit of the fuel tank pressure sensor between the sensor and S206. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | --
30 | Refer to Evaporative Emission Control System Operation Description for the EVAP system hose routing diagram used in the following procedure.

1. Remove the ORVR vent line from the EVAP canister and plug the hose.
2. Remove the EVAP vapor line from the EVAP canister and plug the hose.
3. Attempt to pressurize the EVAP system to the specified value with the J 41413 EVAP pressure/purge cart and HOLD.
4. Locate any leaks in the EVAP and fuel supply systems using the J 41416 ultrasonic leak detector. If necessary lower the fuel tank in order to check the condition of the fill limiter vent valve and the rollover valve. Be sure to check the fuel sender assembly for a correct seal.

Were any EVAP system or fuel supply system leaks found?

56 mm Hg (30 in. H2O)

Go to Step 32

Go to Step 31

31 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Is the action complete? | -- | Go to Step 48 | --
32 | Repair or replace the leaking EVAP system or fuel tank component. Is the action complete? | -- | Go to Step 48 | --
33 | Measure the resistance of the EVAP pressure switching solenoid with a DMM. Is the resistance less than the specified value? | 27 ohms at 20°C (68°F) | Go to Step 34 | Go to Step 35
34 | Replace the EVAP pressure switching solenoid and the PCM. Refer to Evaporative Emission Pressure Switching Solenoid Replacement and to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | --
35 | Replace the EVAP pressure switching solenoid. Refer to Evaporative Emission Pressure Switching Solenoid Replacement . Is the action complete? | -- | Go to Step 48 | --
36 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | Go to Step 48 | --
37 |

1. Check the solenoid control circuit for a short to ground.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

27 ohms at 20°C (68°F)

Go to Step 48

Go to Step 47

38 | Notice: The EVAP canister may have released carbon particles which caused this part to fail and may cause damage to other components. Check the EVAP canister for loose carbon before returning the vehicle to service. Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Is the action complete?

--

Go to Step 48

--

39 | Measure the resistance of EVAP canister vent valve with a DMM. Is the resistance less than the specified range? | 25-30 ohms at 20°C (68°F) | Go to Step 40 | Go to Step 41
40 | Replace the EVAP canister vent valve and the PCM. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement and Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | --
41 | Replace the EVAP canister vent valve . Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 48 | --
42 | Replace the EVAP canister purge valve and the PCM. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement and Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | --
43 |

1. Perform the scan tool Clear DTC Information function.
2. Place the vehicle into Check mode using the scan tool.
3. Operate the vehicle within the Freeze Frame conditions as specified or until the EVAP Purge test is complete. Refer to the Test Description.

Did a DTC P0446 set?

--

Go to Step 44

Go to Diagnostic Aids

44 |

1. Remove the EVAP canister. Refer to Evaporative Emission Canister Replacement .
2. Visually and physically inspect the EVAP canister for cracks or signs of damage.
3. Perform a comprehensive inspection of the EVAP canister. Refer to Evaporative Emission Control System Diagnosis .
4. Replace the EVAP canister if the canister is damaged or fails any inspections.

Was the EVAP canister replaced?

--

Go to Step 48

Go to Step 46

45 |

1. Inspect the control circuit of the EVAP canister purge valve for an open or a short.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 48

Go to Step 47

46 |

1. Inspect the control circuit of the EVAP canister vent valve for an open or a short.
2. Inspect the control circuit of the EVAP pressure switching solenoid for an open or a short.
3. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a wiring fault found and repaired on either solenoid circuit?

--

Go to Step 48

Go to Step 47

47 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | --
48 |

1. Perform the scan tool Clear DTC Information function.
2. Operate the vehicle within the Freeze Frame data that set the original DTC.
3. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK