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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 DTC P0442

Circuit Description

During specific operating conditions, the engine control module (ECM) performs various tests on the evaporative emission system. The system tests consist of the following series of events. After ensuring that the evaporative emission (EVAP) purge solenoid valve duty cycle has dropped to 0 percent, indicating that the valve is closed, the ECM commands the EVAP canister vent solenoid valve closed, sealing the system. The ECM monitors the accumulation of vapor pressure within the fuel tank via the fuel tank pressure (FTP) sensor. The EVAP test is aborted if the vapor pressure is too high. If any vapor pressure is measured, the pressure will be used later in order to compensate for a pressure reading during the small leak detection test. If a vacuum is measured which exceeds a calculated limit during vapor accumulation, diagnostic trouble code (DTC) P0440 will set. The EVAP canister purge solenoid valve is then opened. Simultaneously, the vent solenoid is opened. If the vapor pressure does not bleed off or bleeds off too slowly, DTC P0440 is set. Once the EVAP purge solenoid valve reached the desired position for the remainder of the diagnostic test, the vent solenoid will be closed again. This causes a vacuum to be applied to the entire EVAP system. The ECM monitors the vacuum level within the system. If the desired vacuum level cannot be achieved, or if the vacuum level is reached but took too much time, DTC P0455 will set. Once the desired vacuum level is reached, the purge solenoid is closed, sealing the system. The ECM continues to monitor the fuel tank pressure sensor signal, measuring the rate of vacuum decay. If the system holds vacuum, the vent solenoid is opened and the test is completed. In addition to the system tests, the ECM monitors the circuit integrity of the purge solenoid (DTC P0443), the vent solenoid (DTC P0446) and the fuel tank pressure sensor (DTC P0450).

Conditions for Running the DTC
    • DTCs P0100, P0115, P0116, P0130-P0161, P0300-P0306, P0443, P0446, P0450, P0500, P0506, P0507, P0560, P1120, or P1220 are not set.
    • The vehicle speed is 0 km/h (0 mph).
    • The engine is at idle.
    • The engine coolant temperature (ECT) at start is between -8°C and +75°C (+17-167°F).
    • Fuel system is in Closed Loop.
    • The engine load is less than 30 percent.
    • The intake air temperature (IAT) is between -8°C and +50°C (+17-122°F).
    • The system voltage is more than 11 volts.
    • The engine run time is at least 17 minutes.
    • The secondary air injection (AIR) system is inactive.
    • The secondary AIR system diagnostic is not running.
    • The short term fuel trim at the beginning of the test is more than -5 percent.

Conditions for Setting the DTC

The vacuum in the EVAP system decays at too fast a rate 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 fuel tank assembly consists of an inner fuel tank, EVAP canister, ORVR system and the associated plumbing all encased within an outer fuel tank housing. The outer housing contains a tube that allows air between the inner tank and the outer housing to vent. A leak in any of the internal components of the fuel tank assembly will exit this vent. The vent is located in front of the fuel tank above the fuel filter. If a leak is detected by air exiting this vent while the EVAP system is pressurized, the fuel tank assembly will require replacement. The internal components of the fuel tank assembly are not serviceable. A similar vent for the fuel tank pressure sensor is also located in front of the fuel tank. A leak from this vent while the EVAP system is pressurized indicates the fuel tank pressure sensor is leaking.

Check for the following conditions:

    • A damaged, loose, or incorrect fuel cap
    • A disconnected or damaged EVAP vent hose
    • An EVAP purge valve that is not closing properly
    • An EVAP vent valve that is not closing or not sealing when closed
    • A leaking fuel sender assembly O-ring
    • A leaking fuel tank or fuel filler neck
    • Inspect the purge line and valve for traces of carbon. Any carbon escaping from the canister may prevent the valve from closing properly. If traces of carbon are found, disconnect both ends of the purge line and blow out any contaminants by using the pressurized gas from the J 41750 EVAP Pressure/Purge Cart. Replace the purge valve and the canister/fuel tank.

Test Description

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

  1. 20.37 mm Hg (10.86 in. H2O) is the maximum value displayed on the scan tool even though the actual pressure in the system may be higher. If the pressure cannot be attained on the fuel tank pressure sensor, this indicates there may be a restriction in the purge line or a skewed sensor. These conditions are diagnosed in DTC P0455.

    2.

  2. Inspect the purge valve and lines for traces of carbon. Carbon escaping from the canister may prevent the valve from closing properly. If this condition is found, disconnect both ends of the purge line and blow out any contaminants using the pressurized gas from the EVAP pressure/purge cart. Replace the purge valve and the canister/fuel tank.

DTC P0442 - Evaporative Emission (EVAP) System Small Leak Detected

Step

Action

Values

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

Is DTC P0443, P0446, P0450, or P0455 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Perform a visual and physical inspection of the EVAP system before continuing with the diagnostic table. Check for the following conditions:
    2. • Disconnected, kinked, or deteriorated hoses/lines
    • Loose hose connections
    • A missing or a loose fuel cap
    • Obvious damage to any of the system components
  2. Repair as necessary.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 4

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

Is the fuel tank pressure within the specified range?

-1.87 to +1.87 mm Hg (-1 to +1 in H2O)

Go to Step 5

Go to DTC P0450

5

Important: Before continuing with diagnosis, zero the EVAP pressure and vacuum gauges on J 41750 EVAP Pressure/Purge Cart. Refer to the tool operating instructions.

  1. Connect the EVAP pressure/purge cart to the EVAP service port.
  2. Replace the fuel cap.
  3. Install the scan tool.
  4. Turn ON the ignition.
  5. Using the scan tool, command the vent valve ON, closed.
  6. Pressurize the EVAP system using the pressure/purge cart to the first specified value. Monitor the pressure using the gauge on the cart.
  7. Rotate the valve on the cart to HOLD and observe the pressure gauge.

Does the pressure drop below the second value within 2 minutes?

28.02 mm Hg (15 in H2O)

18.68 mm Hg (10 in H2O)

Go to Step 7

Go to Step 6

6

  1. Adjust the system pressure to the first specified value.
  2. Observe the fuel tank pressure on the scan tool.

Is the fuel tank pressure at or more than the second specified value?

20.55 mm Hg (11 in H2O)

18.68 mm Hg (10 in H2O)

Go to Diagnostic Aids

Go to DTC P0455

7
  1. Turn OFF the ignition.
  2. Disconnect the vent hose from the fuel tank at the vent valve.
  3. Block off the hose using a suitable stopper.
  4. Pressurize the system to the first specified value with the gauge on the cart.
  5. Rotate the valve on the cart to HOLD.

Does the pressure drop below the second value within 2 minutes?

28.02 mm Hg (15 in H2O)

18.68 mm Hg (10 in H2O)

Go to Step 8

Go to Step 11

8
  1. Disconnect the purge line at the purge valve.
  2. Block off the line using a suitable stopper.
  3. Pressurize the system to the first specified value with the gauge on the cart.
  4. Rotate the valve on the cart to HOLD.

Does the pressure drop below the second value within 2 minutes?

28.02 mm Hg (15 in H2O)

18.68 mm Hg (10 in H2O)

Go to Step 9

Go to Step 10

9
  1. With the cart connected to the EVAP service port continuously pressurize the EVAP system by leaving the cart control knob in the pressurize position.
  2. Test for leaks with the J 41416 Ultrasonic Leak Detector. Test the following areas and repair or replace as necessary:
    3. • Fuel tank--Refer to Diagnostic Aids.
    • Filler cap/fill pipe area
    • Sending unit and sending unit to tank seal
    • Fuel tank pressure sensor and seal
    • Purge lines
    • EVAP service port
    • Vent hose from the fuel tank to the vent valve

Did you find and correct the condition?

--

Go to Step 12

--

10

Replace the purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Turn ON the ignition.
  2. Using the scan tool, command the vent valve ON, closed.
  3. Pressurize the EVAP system to the first specified value using the J 41750 . Monitor the pressure using the gauge on the cart.
  4. Rotate the valve on the cart to HOLD and observe the pressure gauge.

Does the pressure drop below the second value within 2 minutes?

28.02 mm Hg (15 in H2O)

18.68 mm Hg (10 in H2O)

Go to Step 7

Go to Step 13

13
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 14

Go to Step 2

14

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