GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Sonoma Pickup - 2WD 🢒 DTC 🢒 DTC P0442

Description

The evaporative emission (EVAP) small leak test applies vacuum to the EVAP system and monitors vacuum decay. The powertrain control module (PCM) monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the PCM turns the EVAP canister purge valve ON, or open, and the EVAP vent valve ON, or closed. This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the PCM turns the purge valve OFF, or closed, sealing the system, and monitors the FTP sensor input in order to determine EVAP system vacuum decay. If the system detects a leak larger than a calibrated amount diagnostic trouble code (DTC) P0442 will set.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0452, or P0453 are not set.
    • The ignition voltage is between 10-18 volts.
    • The barometric pressure (BARO) is more than 75 kPa.
    • The fuel level is between 15-85 percent.
    • The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
    • The intake air temperature (IAT) is between 4-30°C (39-86°F).
    • The start up ECT and IAT are within 9°C (16°F) of each other.
    • The vehicle speed sensor (VSS) is less than 121 kmh (75 mph).

Conditions for Setting the DTC

The EVAP system can achieve vacuum but a vacuum decay is detected during the diagnostic test.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. To aid in locating intermittent leaks, use the J 41413 EVAP Pressure/Purge Diagnostic Station to pressurize the EVAP system. Move all EVAP components while testing with the J 41416 Ultrasonic Leak Detector.

Test Description

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

  1. This step verifies that a failure condition is active.

    2.

  2. This step verifies that repairs are complete.

    3.

  3. This step verifies that no other condition is present.

Step

Action

Values

Yes

No

Schematic Reference: Evaporative Emissions Hose Routing Diagram

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Is DTCs P0446, P0452, P0453, P0461, P0462, P0463, or P1441 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Inspect the EVAP system for the following conditions:
    2. • Loose, missing or damaged service port schrader valve
    • Loose, incorrect, missing, or damaged fuel fill cap
    • A damaged EVAP canister purge valve
  2. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Inspect the EVAP system for the following conditions:
    4. • Disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses
    • A damaged EVAP canister vent valve or EVAP canister

Did you find and correct the condition?

--

Go to Step 6

Go to Step 4

4

Important: Always zero the EVAP pressure and vacuum (in. H2O) gages on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.

  1. Install the J 41415-40 Fuel Tank Cap Adapter.
  2. Connect the J 41413 EVAP Pressure/Purge Diagnostic Station and the fuel tank cap to the J 41415-40 .
  3. Turn ON the ignition, with the engine OFF.
  4. Use a scan tool to clear the DTCs from the PCM.
  5. Command the EVAP vent valve ON with a scan tool.
  6. Pressurize the EVAP system to the specified value with the J 41413 .
  7. Place the control knob on the J 41413 to the OFF/HOLD position.
  8. Monitor the EVAP system pressure on the J 41413 for 5 minutes.

Does the EVAP system pressure remain constant?

15 in H2O

Go to Diagnostic Aids

Go to Step 5

5
  1. With the J 41413 , continuously attempt to pressurize the EVAP system.

    2. Important: It may be necessary to partially lower the fuel tank to inspect components located in the upper portion of the tank.

  2. With the J 41416 Ultrasonic Leak Detector, inspect for leaks in the following locations:
    3. • The EVAP system purge pipe--Refer to Evaporative Emission Hoses/Pipes Replacement - Chassis/Canister .
    • The EVAP vapor pipe--Refer to Evaporative Emission Hoses/Pipes Replacement - Engine .
    • The EVAP vent hose/pipe
    • The fuel fill pipe/hose and fuel fill cap
    • The EVAP canister--Refer to Evaporative Emission Canister Replacement .
    • The EVAP canister vent valve--Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .
    • The EVAP canister purge valve--Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .
    • The fuel sender assembly and/or seal--Refer to Fuel Sender Assembly Replacement .
    • The FTP sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fill limiter vent valve, pressure relief valve, rollover valves, and fuel tank--Refer to Fuel Tank Replacement .

Did you find and repair the condition?

15 in H2O

Go to Step 6

Go to Diagnostic Aids

6

  1. Turn ON the ignition, with the engine OFF.
  2. Command the EVAP vent valve ON with a scan tool.
  3. Pressurize the EVAP system to the specified value with the J 41413 .
  4. Place the control knob on the J 41413 to the OFF/HOLD position.
  5. Monitor the EVAP system pressure on the J 41413 for 5 minutes.

Does the EVAP system pressure remain constant?

15 in H2O

Go to Step 7

Go to Step 2

7

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