GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 Cutlass 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 DTC P0446 Evaporative Emission (EVAP) Vent System Performance

Object Number: 70615 Size: LF
Engine Controls Components
Cell 23: EVAP and EGR Controls
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The evaporative system (EVAP) includes the following components:

    • The fuel tank
    • The EVAP vent solenoid
    • Fuel tank pressure sensor
    • The fuel pipes and hoses
    • The fuel vapor lines
    • The fuel cap
    • The EVAP canister
    • The purge lines
    • The EVAP canister purge solenoid valve
    • The EVAP service port

The EVAP system is checked by applying vacuum to the EVAP system and by monitoring for a vacuum decay. The Powertrain Control Module (PCM) monitors the vacuum level through the fuel tank pressure sensor signal. At an appropriate time, the EVAP canister purge solenoid valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge solenoid valve is turned OFF, sealing the system.

A restricted or blocked EVAP canister vent path is detected by drawing a vacuum on the EVAP system, turning OFF the EVAP vent solenoid and the EVAP canister purge solenoid valve, with the EVAP vent solenoid open and the EVAP purge pulse width modulation (PWM) 0 percent, and monitoring the fuel tank vacuum sensor signal. With the EVAP vent solenoid open, any vacuum in the system should decrease quickly unless the vent path is blocked. A blockage can be caused by the following conditions:

    • A malfunctioning EVAP vent solenoid, stuck closed
    • The vent hose for the following conditions:
       - Plugs
       - Kinks
       - Pinches
    • A shorted EVAP vent solenoid driver circuit
    • A plugged evaporative canister

If any of these conditions are present, DTC P0446 will set.

Conditions for Setting the DTC
    • The BARO is greater than 75 kPa.
    • The intake air temperature is between 5°C and 29°C (41°F and 84°F) at engine start up.
    • The engine coolant temperature is between 5°C and 29°C (41°F and 84°F) at engine start up.
    • The Intake Air Temperature is not more than 1°C (2°F) greater than the Engine Coolant Temperature at start up.
    • The Engine Coolant Temperature is not more than 7°C (12°F) greater than the Intake Air Temperature at start up.
    • The fuel tank level is between 26 percent and 74 percent.
    • The TP sensor is between 7 percent and 35 percent.
    • The EVAP solenoid is at 50 percent PWM within 65 seconds of the engine run time.
    • The EVAP System detects a vacuum and is unable to release the vacuum during the diagnostic test.
    • DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134 and P1133 are not set.

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will illuminate.
    • The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
    • The EVAP purge function is disabled until the diagnostic passes.
    • A history DTC stores.

Conditions for Clearing the MIL/DTC
    • The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs a pass.
    • A history DTC will clear after 40 consecutive warm up cycles without a malfunction.
    • A scan tool can clear the DTCs.

Diagnostic Aids

Although this DTC is considered a type A diagnostic (refer to Serial Data Communications ), this DTC acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports that the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure does not report to the diagnostic executive or display on a scan tool. A passing system always reports to the diagnostic executive immediately.

If a DTC P0460 is set along with an EVAP System DTC, the EVAP DTC cannot be considered valid until you repair and clear DTC P0460.

Check for the following conditions:

    • A poor connection at the PCM. Inspect the harness connectors for the following conditions:
       - Backed out terminals
       - Improper mating
       - Broken locks
       - Improperly formed connectors
       - Damaged terminals
       - A poor terminal to wire connection
    • A damaged harness. Inspect the wiring harness to the EVAP vent solenoid and the fuel tank pressure sensor for an intermittent open or short circuit.
    • A kinked, pinched, or plugged vent hose. Verify that the vent hose between the canister and the EVAP vent solenoid is not restricted.
    • Refer to Evaporative Emission System Cleaning for further procedure.

Test Description

The number(s) below refer(s) to the step number(s) on the Diagnostic Table.

  1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.

    2.

  2. If a vent solenoid electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction will very likely correct the condition that set DTC P0446.

    3.

  3. This step checks the fuel tank pressure sensor at the ambient pressure.

    4.

  4. This step verifies that the fuel tank pressure sensor accurately reacts to the EVAP system pressure changes.

  5. This step checks for a blocked EVAP canister.

    6.

  6. This step duplicates the Powertrain On-Board Diagnostic test.

DTC P0446-Evaporative Emission (EVAP) Control System Vent Control

Step

Action

Value(s)

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
  1. Turn ON the ignition switch leaving the engine OFF.
  2. Install a scan tool.
  3. Check the PCM and the BCM for DTCs with the scan tool.

Is DTC P0452, P0453 or P0461 also set?

--

Go to Component DTC table

Go to step 3

3

  1. Command the EVAP canister purge solenoid valve ON and OFF with the scan tool.
  2. Command the vent solenoid ON and OFF with the scan tool.

Does the purge valve and the vent solenoid click when commanded ON and OFF?

--

Go to Step 4

Go to Powertrain Control Module Outputs Diagnosis

4

  1. Turn OFF the ignition switch.
  2. Disconnect the vapor line from the fuel tank at the EVAP canister.
  3. Turn ON the ignition switch leaving the engine OFF.
  4. Check the Fuel Tank Pressure sensor value with the scan tool.

Is the Fuel Tank Pressure at the specified value?

0 mmHg

(-2.4-2.4 mmHg)

(-1.28-1.28 in. H2O)

Go to Step 6

Go to Step 5

5
  1. Turn OFF the ignition switch.
  2. Check the EVAP vapor line from the fuel tank to the EVAP canister for the following conditions:
    3. • Pinched vapor line
    • Kinked vapor line
    • Plugged vapor line
  3. Repair the condition as necessary.

Was a repair necessary?

--

Go to Step 12

Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

or

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

6

Important: : Before continuing with the diagnosis, zero the EVAP Pressure and Vacuum gauges on the J 41413 EVAP pressure/purge Diagnostic Station (refer to tool operating instructions).

  1. Reconnect all the EVAP hardware that was previously disconnected.
  2. Connect the J 41413 EVAP pressure/purge Diagnostic Station to the EVAP service port.
  3. Command the EVAP vent solenoid ON (closed) with the scan tool.

    4. Important: Do not exceed the pressure given in the first specified value.

  4. Pressurize the EVAP system to the first specified value by using the J 41413 EVAP pressure/purge Diagnostic Station (monitor the pressure using the gauge on the station).
  5. Observe the Fuel Tank Pressure value on the scan tool.

Is the Fuel Tank Pressure at the second specified value?

9.3 mmHg

(5 in. H2O)

12 mmHg

(-7.2-16.8 mmHg)

(3.85-8.99 in. H2O)

Go to Step 7

Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

or

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

7
  1. Maintain the EVAP pressure at the first specified value.
  2. Command the EVAP vent solenoid OFF (open) with the scan tool, while observing the EVAP pressure gauge on the J 41413 EVAP pressure/purge Diagnostic Station.

Does the EVAP pressure return to the second specified value within 5 seconds?

1.25 kPa

(5 in. H2O)

0 kPa

(0 in. H2O)

Go to Diagnostic Aids

Go to Step 8

8

  1. Disconnect the large vent hose from the EVAP canister marked air.
  2. Switch the rotary switch on the J 41413 EVAP pressure/purge Diagnostic Station to PURGE.
  3. Start the engine.
  4. Allow the engine to reach the normal operating temperature.
  5. Command the EVAP purge solenoid valve ON with the scan tool.
  6. Observe the vacuum gauge for 5 seconds while holding the engine speed at the first specified value.

Does the vacuum remain below the second specified value?

2,500 RPM

2.49 kPa

(10 in. H2O)

Go to Step 9

Go to Step 11

9
  1. Turn OFF the ignition switch.
  2. Inspect the EVAP vent hose between the EVAP canister and the EVAP vent solenoid for the following conditions:
    3. • Kinked hose
    • Pinched hose
    • Plugged hose
  3. If a problem is present, repair the problem as necessary.

Were there any necessary repairs?

--

Go to Step 12

Go to Step 10

10

    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.

  1. Replace the EVAP vent solenoid. Refer to the Evaporative Emission Vent Valve Replacement .
  2. If carbon particles are found in the component refer to the Evaporative Emission System Cleaning .

Is the action complete?

--

Go to Step 12

--

11
  1. Turn OFF the ignition switch.

    2. 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.

  2. Replace the EVAP canister. Refer to the Evaporative Emission Canister Replacement .
  3. Check for carbon particles that are loose and coming out of the EVAP canister, refer to the Evaporative Emission System Cleaning .

Is the action complete?

--

Go to Step 12

--

12

  1. Reconnect all the EVAP hardware that was previously disconnected.
  2. Turn ON the ignition switch leaving the engine OFF.
  3. Command the EVAP vent solenoid ON (closed) with the scan tool.
  4. Pressurize the EVAP system to the first specified value.
  5. Switch the rotary switch on the J 41413 EVAP pressure/purge Diagnostic Station to HOLD.
  6. Command the EVAP vent solenoid OFF (open) with the scan tool, while observing the J 41413 EVAP pressure gauge on the station.

Does the EVAP pressure return to the second specified value within 5 seconds?

9.34 mmHg

(5 in. H2O)

0 mmHg

(0 in. H2O)

Go to Step 13

Go to Step 3

13
  1. Clear the DTCs with the scan tool.
  2. Start the engine.
  3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that the diagnostic ran and passed?

--

Go to Step 14

Go to Step 3

14

Check to see if any additional DTC are set.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to applicable DTC table

System OK