For 1990-2009 cars

### Circuit Description

The DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected diagnostic monitors the operation of the EVAP system. The evaporative emission (EVAP) control system leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring vacuum decay. The powertrain control module (PCM) monitors the vacuum level via the fuel tank pressure (FTP) sensor input. The PCM turns ON the EVAP canister purge valve and the EVAP vent valve, allowing the engine manifold pressure to draw a small vacuum on the entire EVAP system. If sufficient vacuum cannot be sustained over a given period of time, a small leak or a malfunction is suspected and DTC P0442 sets. The EVAP system used with this powertrain is part of an on-board refueling vapor recovery (ORVR) fuel system.

The EVAP system as defined by federal regulation includes the following components:

• | The fuel tank

• | The EVAP canister vent valve

• | The FTP sensor

• | The fuel pipes and hoses

• | The vapor lines

• | The fuel filler cap

• | The fuel tank pressure control valve

• | The EVAP canister

• | The purge lines

• | The EVAP canister purge valve

### Condition for Running the DTC

• | DTC P0444, DTC P0445, DTC P0447, DTC P0448, DTC P0451, DTC P0452, DTC P0453, DTC P0455, DTC P0496 are not set.

• | Engine coolant temperature is between 70-110°C (158°F-230°F)

• | Intake air temperature is between -10°C to +62°C (14°F-144°F).

• | Barometric pressure (BARO) is more than 75 kPa.

• | Fuel tank level is less than 75 percent.

• | Throttle position (TP) sensor input remains steady.

• | The engine is running.

• | The EVAP canister purge solenoid and vent solenoids are both closed.

### Conditions for Setting the DTC

• | The expected increase in the internal pressure of the fuel tank is more than a specified value.

• | The diagnostic may take up to 20 minutes to run.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | 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

• | MIL turns OFF after 3 consecutively passing trips without a fault present.

• | History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

If a DTC P0442 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Evaporative Emission System Set .

A faulty or erratic fuel level sensor can cause DTC P0442 to set. Use the scan tool in order to check the operation of the fuel level sensor. If the accuracy of the fuel level sensor is suspect, refer to DTC P0461 in Instrument Panel, Gages, and Console.

The EVAP purge diagnostic checks for many of the faults that can cause DTC P0442 to set. If the EVAP Purge test passes the cause of the DTC P0442 is probably intermittent. Clear the DTCs. Road test the vehicle while monitoring the EVAP Purge in the MIL/System Status selection under System Information on the scan tool. When the EVAP Purge indicates complete with a YES status, check for DTC P0442 under Last Test Failed. If there is no DTC P0442 indicated, the DTC is intermittent and the purge system diagnostic is indicating OK at this time.

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 control system electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0442 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 Diagnostic System Check-Engine Controls 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 operation of the FTP sensor. If the FTP sensor does not indicate near zero pressure when the fuel filler cap is removed, the FTP sensor or circuit might be faulty. The FTP sensor can be checked by using the diagnostic procedures in DTC P0450.

3. This step checks the components that supply manifold vacuum to the EVAP canister purge valve.

4. This step checks the operation of the EVAP canister purge valve. The duty cycle control of the EVAP canister purge valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.

5. This step checks the operation of the EVAP canister vent valve. The output control of the EVAP canister vent valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.

6. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0442 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0442 appears in the Not Ran Since Code Cleared list, the DTC P0442 diagnostic has not yet run. When the DTC P0442 does not appear in the Not Ran Since Code Cleared list, the DTC P0442 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0442 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Are any EVAP codes set other than a DTC P0442 or a DTC P0455? | -- | Go to Diagnostic Trouble Code (DTC) List | Go to Step 3
3 |

1. Observe the Fuel Tank Pressure (FTP) Sensor parameter with a scan tool.
2. Remove the fuel filler cap.

Is the fuel tank pressure within the specified range with the fuel filler cap removed?

0.0-0.9 mm Hg (0.0-0.5 in H2O)

Go to Step 4

Go to DTC P0451

4 | Visually inspect the entire EVAP control system for any of the following conditions:

• | Loose hose connections

• | Damaged or deteriorated hoses

• | Clogged hoses

• | Missing or damaged components

• | Loose or incorrect fuel filler cap

Was a problem found?

--

Go to Step 7

Go to Step 5

5 | Important: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.

1. Turn OFF the ignition.
2. Connect theJ 41413-200 Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source.
3. Install theJ 41415-30 Fuel Tank Cap Adapter to the fuel fill pipe.
4. Connect the fuel fill cap to theJ 41415-30 .
5. Connect the nitrogen/smoke supply hose to the J 41415-30 .
6. Turn ON the ignition, with the engine OFF
7. Command the EVAP vent solenoid closed with a scan tool.
8. Turn the nitrogen/smoke valve on the control panel to SMOKE.
9. Use the remote switch to introduce smoke into the EVAP system.
10. Disconnect the EVAP purge line from the purge solenoid.
11. Re-connect the EVAP purge line to the purge solenoid once smoke is observed.
12. Continue to introduce smoke into the EVAP system for an additional 60 seconds.
13. Inspect the entire EVAP system for exiting smoke with the High Intensity White Light.
14. Continue to introduce smoke at 15 second intervals until the leak source has been located

Did you find a leak in the EVAP control system?

--

Go to Step 6

Go to Step 7

6 | Repair or replace any leaking or faulty EVAP control system components. Is the action complete? | -- | Go to Step 24 | --
7 |

1. Check for any of the following conditions at the EVAP canister purge valve:

• | No manifold vacuum from the intake manifold vacuum port

• | Leaking or damaged vacuum hoses

• | Restricted vacuum hoses or passages

2. Repair any condition found during the above checks.

Was a repair necessary?

--

Go to Step 24

Go to Step 8

8 | Caution: Refer to Fuel Vapors in Evaporative Emission Components Caution in the Preface section.

1. Turn ON the ignition, leaving the engine OFF.
2. Disconnect the vacuum hoses to the EVAP canister purge valve from the intake manifold and from the EVAP canister.
3. Blow air into the vacuum hose that was disconnected from the EVAP canister. Air should not pass through the EVAP canister purge valve and exit from the intake manifold hose.
4. Command the EVAP canister purge valve ON and adjust the duty cycle to 100 percent with the scan tool. Refer to Scan Tool Output Controls .
5. Blow air into the vacuum hose that was disconnected from the EVAP canister. Air should pass through the EVAP canister purge valve and exit from the intake manifold hose.

Does the EVAP canister purge valve pass both inspections?

--

Go to Step 9

Go to Step 17

9 | Caution: Refer to Fuel Vapors in Evaporative Emission Components Caution in the Preface section.

1. Turn OFF the ignition.
2. Remove the EVAP canister vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .
3. Blow air into the EVAP canister vent valve port, located on the side that was connected to the EVAP canister air filter.

Did the air pass through to the other side of the EVAP canister vent valve?

--

Go to Step 10

Go to Step 20

10 |

1. Turn ON the ignition, leaving the engine OFF.
2. Command the EVAP canister vent valve ON using a scan tool. Refer to Scan Tool Output Controls .
3. Blow air into the EVAP canister vent valve port, located on the side that was connected to the EVAP canister air filter.

Was the air unable to pass through the EVAP canister vent valve?

--

Go to Step 11

Go to Step 18

11 |

1. Continue to blow air into the EVAP canister vent valve.
2. Command the EVAP canister vent valve OFF with the scan tool.

Did the air pass through the EVAP canister vent valve when the scan tool commanded the vent valve OFF?

--

Go to Step 12

Go to Step 18

12 | Caution: Refer to Fuel Vapors in Evaporative Emission Components Caution in the Preface section.

1. Disconnect the vacuum/vapor hoses from the EVAP canister.
2. Blow air into the tank port of the EVAP canister. There should be no restriction of air flow through the canister and out the purge pipe and the air port. Refer to Evaporative Emission Control System Diagnosis .

Did the EVAP canister pass the test?

--

Go to Step 13

Go to Step 15

13 | Caution: Refer to Fuel Vapors in Evaporative Emission Components Caution in the Preface section.

1. Remove the fuel tank pressure (FTP) control valve. Refer to Fuel Tank Pressure Control Valve Replacement .
2. Connect a vacuum hose to the canister side port of the FTP control valve.

Important: There will be some resistance, but air should flow steadily.

3. Blow air into the hose on the FTP control valve.

Did the air flow through the valve to the tank port side?

--

Go to Step 14

Go to Step 21

14 | Important: The FTP control valve allows vapor to flow from the fuel tank to the canister when the fuel tank pressure is greater than canister pressure by more than 3.5 kPa (0.5 psi).

1. Move the vacuum hose to the fuel tank port of the FTP control valve.
2. Blow hard into the hose connected to the tank port side of the FTP control valve. Air should flow easily through the valve and out of the canister port.

Did the FTP control valve pass this test?

--

Go to Step 16

Go to Step 21

15 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Is the action complete? | -- | Go to Step 24 | --
16 |

1. Inspect the EVAP canister air filter and hoses for restrictions or blockage.
2. Repair as necessary. Refer to Evaporative Emission Canister Filter Replacement .

Was a repair necessary?

--

Go to Step 24

Go to Diagnostic Aids

17 |

1. Connect a test lamp from B+ to the purge valve control circuit by backprobing at the PCM. Refer to Powertrain Control Module Connector End Views .
2. Command the EVAP canister purge valve ON and adjust the duty cycle to 100 percent with the scan tool. Refer to Scan Tool Output Controls .

Does the test lamp flash and then illuminate steadily at the 100 percent duty cycle?

--

Go to Step 22

Go to Step 19

18 |

1. Connect a test lamp from B+ to the vent valve control circuit by backprobing at the PCM. Refer to Powertrain Control Module Connector End Views .
2. Command the EVAP canister vent valve ON using the scan tool. Refer to Scan Tool Output Controls .

Does the test lamp illuminate only when the valve is commanded ON?

--

Go to Step 20

Go to Step 19

19 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Repair as necessary. Was a repair necessary? | -- | Go to Step 24 | Go to Step 23
20 | Replace the EVAP canister vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 24 | --
21 | Replace the FTP control valve. Refer to Fuel Tank Pressure Control Valve Replacement . Is the action complete? | -- | Go to Step 24 | --
22 | Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 24 | --
23 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 24 | --
24 |

1. Turn OFF the ignition.
2. Remove the DOME fuse for 30 seconds.
3. Install the DOME fuse.
4. Reset the radio clock time. Refer to Radio/Audio System Description and Operation in Entertainment.
5. Start the engine.
6. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or until the DTC P0442 diagnostic test has run.

Does the DTC run and pass?

--

Go to Step 25

Go to Step 2

25 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK