GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 DTC P0442

Circuit Description

The powertrain control module (PCM) tests the evaporative emission (EVAP) system for the following conditions:

    • Large and small leaks
    • Excess vacuum
    • Purge flow during non-commanded conditions
    • Fuel level and fuel pressure sensor faults
    • EVAP purge and vent valve faults

The PCM monitors the fuel tank pressure sensor in order to determine the level of vacuum or pressure in the EVAP system. The PCM commands both the EVAP purge solenoid and the EVAP vent valve ON when the Conditions for Running the DTC are met in order to apply an engine vacuum to the EVAP system. The PCM commands the EVAP purge solenoid OFF once the system has reached a predetermined level of vacuum. The EVAP system should HOLD the vacuum in the sealed system. The PCM sets this diagnostic trouble code (DTC) in order to indicate a small leak if the EVAP system fails to hold a predetermined level of vacuum for a predetermined length of time. This DTC sets after failing the above test twice.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0110, P0112, P0113, P0115, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121, or P1122 are not set.
    • The barometric pressure (BARO) is more than 75 kPa.
    • The fuel level is between 15-85 percent of full capacity.
    • The throttle position (TP) sensor angle is less than 75 percent.
    • The vehicle speed is less than 102 km/h (65  mph).
    • 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.

Conditions for Setting the DTC

The vacuum in the EVAP system decays or leaks at too fast a rate.

Important: This DTC does NOT report a first failed test. A first fail of this DTC will have a scan tool status as Not Run. Use the scan tool data display parameter of EVAP test result to determine if this DTC has failed or passed for this ignition cycle.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/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

Important: 

   • Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
   • An accurate indication of fuel level is required for the PCM to properly pass or fail this DTC. Always diagnose fuel level sensor DTCs before performing this DTCs diagnostic table. Always inspect for fuel level sensor DTCs stored as History.
   • The Service Bay Test may have to be performed in cold ambient air temperatures when the vehicle is running a winter grade fuel. The scan tool displays a message when the service bay test does not run.
   • Inspect for charcoal release from the vapor canister. Refer to Evaporative Emission System Cleaning procedure.

Conditions for Running the Service Bay Test
    • The battery voltage is between 10.5-17.5 volts.
    • The fuel level is between 15-85 percent of the full capacity.
    • The engine temperature is between 3.5-35°C (38-95°F).

Perform a physical inspection of the EVAP system. Inspect for the following conditions:

    • A loose, missing, defective, or incorrect fuel tank cap
    • Incorrectly routed or defective EVAP system vacuum and vapor lines
    • A malfunctioning or damaged vapor canister
    • Charcoal release from the vapor canister--Refer to Evaporative Emission System Cleaning .

The vacuum and pressure in the EVAP system is measured in inches of water (H2O). Most gauges measure vacuum in inches of mercury (Hg) and pressure in pounds per square inch (psi). The following shows how the values compare:

in H2O

in Hg

psi

1in H2O

0.07 in Hg

0.0361 psi

5 in H2O

0.36 in Hg

0.180 psi

10 in H2O

0.73 in Hg

0.361 psi

15 in H2O

1.10 in Hg

0.541 psi

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 and that no other condition is present.

Step

Action

Values

Yes

No

Schematic Reference: Emission Hose Routing Diagram and 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

Does the scan tool indicate DTC P0443 or DTC P0449 are 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 dust cap and/or 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

  1. With a scan tool, capture and record the fail record data and clear the DTCs.
  2. Perform the Service Bay Test. Refer to Service Bay Test .

Does the scan tool indicate that the service bay test passed?

--

Go to Diagnostic Aids

Go to Step 5

5

Important: Always zero the EVAP Pressure and vacuum (in. H2O) gauges on the EVAP Pressure Diagnostic Station before proceeding with diagnosis.

  1. Install the J 41415-40 Fuel Fill Cap Adaptor.
  2. Connect the J 41413 Pressure/Purge Diagnostic Station to the fuel fill cap adaptor.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, seal the EVAP system.
  5. With the pressure/purge diagnostic station, continuously pressurize the EVAP system to the specified value.

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

  6. With the J 41416 Ultrasonic Leak Detector inspect for leaks in the following locations:
    7. • The EVAP vent hose
    • The fuel fill pipe/hose and fuel fill cap--Refer to Filler Tube Replacement .
    • 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 fuel tank pressure (FTP) sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fill limiter vent valve, pressure relief valve, rollover valves, permanent EVAP pipes and/or fuel tank--Refer to Fuel Tank Replacement .

Did you find and correct the condition?

15 in H2O

Go to Step 6

Go to Diagnostic Aids

6

Perform the Service Bay Test. Refer to Service Bay Test .

Does the scan tool indicate that the service bay test passed?

--

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