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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Camaro 🢒 DTC 🢒 DTC P0446 Evaporative Emission (EVAP) Vent System Performance

Object Number: 582399 Size: MF
Engine Controls Component Views
EGR and EVAP
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM monitors the performance of the EVAP system by applying a predetermined level of vacuum to the EVAP system and then monitors the vacuum decay rate. The PCM sets this DTC if the vacuum decay rate is greater than a predetermined value.

Conditions for Running the DTC

    • DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0420, P0430, P0452, P0453, P0500, P0502, P0503, P0562, P0563, or HO2S DTCs are not set.
    • The ignition voltage is between 10 and 17 volts.
    • The barometric pressure is more than 75 kPa.
    • The fuel level is between 15 percent and 85 percent of full capacity.
    • The engine coolant temperature is between 4°C (39°F) and 30°C (86°F).
    • The intake air temperature is between 4°C (39°F) and 30°C (86°F).
    • The start up engine coolant temperature and the intake air temperature are within 9°C (16°F) of each other.

Conditions for Setting the DTC

    • The EVAP vacuum decay rate is more than a predetermined value when the vent solenoid is commanded open.
    • The conditions are present for more than 2 seconds.

OR

    • The vacuum present in the EVAP system is more than a predetermined value when the vent solenoid is commanded open during normal purge.
    • The conditions are present for more than 4 seconds.

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.

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

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Important: 

   • Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
   • For any test that requires probing the PCM or a component harness connector, use the J 35616 connector test adapter kit. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

A fuel tank pressure sensor ground circuit that is open will cause this DTC to set. The Fuel Tank Pressure sensor and the Fuel Level sensor share the same ground. IF DTC P0463 is also set, inspect the common ground for an open.

An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose the fuel level sensor DTCs before performing this DTC diagnostic table. Always inspect for fuel level sensor DTCs stored as History.

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 stuck closed EVAP Vent Valve
    • A restricted or blocked EVAP system hose
    • A restricted or stuck closed fuel tank rollover valves
    • A malfunctioning or damaged vapor canister

Inspect for charcoal release from the vapor canister. Refer to Evaporative Emission System Cleaning procedure.

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

in. H2O

in. Hg.

psi

1 in. 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.

    • 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.

Conditions for Running the Service Bay Test

       - The battery voltage is between 10.5 and 17.5 volts.
       - The fuel level is between 15 percent and 85 percent of the full capacity.
       - The engine temperature is between 3.5°C (38°F) and 35°C (95°F).
    • The scan tool displays Test Aborted if any of the above conditions are not met.
    • Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.
    • For an intermittent, refer to Symptoms .

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. An intermittent leak or restriction is indicated if the vehicle passes the Service Bay Test. A fuel tank cap that is loose or off causes this DTC to set.

    If the Service Bay Test can not be run, proceed to step 5. If a fault is not currently present the diagnostic table steps will return you to step 3.

    2.

  2. Testing the vapor canister and the EVAP Vent Valve for restriction.

    3.

  3. A Fuel Tank Pressure sensor that does not correctly respond to pressure (or vacuum) causes this DTC to set. An open Fuel Tank Pressure sensor ground circuit will cause this DTC to set. If the Fuel Tank Pressure sensor does not respond to pressure (or vacuum) inspect the ground circuit for an open.

    The Fuel Tank Pressure sensor range is from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).

    In order to test the Fuel Tank Pressure sensor for vacuum response, command the EVAP Purge Solenoid Valve ON with the engine running and quickly SEAL the system. Leaving the EVAP Purge Solenoid Valve ON for a longer period of time allows a greater level of vacuum to develop.

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. Inspect the EVAP system for the following conditions:
    2. • Improperly routed, kinked or damaged EVAP purge and tank vent lines.
    • A damaged EVAP system component.
  2. Repair the EVAP system as necessary if you find a condition.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 3

3

Important: Ensure that The Conditions for Running the Service Bay Test are met before proceeding with this diagnostic. Refer to Diagnostic Aids.

Perform the EVAP system Service Bay Test.

Does the vehicle pass the Service Bay Test?

--

Go to Diagnostic Aids

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Remove the fuel tank cap.
  3. Turn ON the ignition, with the engine OFF.
  4. Monitor the fuel tank pressure sensor voltage, with a scan tool.

Is the fuel tank pressure sensor voltage less than the specified value?

4 V

Go to Step 5

Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

5

  1. Turn OFF the ignition.
  2. Lower the fuel tank. Refer to Fuel Tank Replacement .
  3. Disconnect the fuel tank vapor and the EVAP purge lines from the EVAP vapor canister.
  4. Plug the canister fitting for the fuel tank vapor line.
  5. Connect the hand held vacuum pump J 23738-A to the EVAP purge line canister fitting.
  6. Turn ON the ignition leaving the engine OFF.
  7. Command the EVAP Vent Valve ON (closed) using the scan tool.
  8. Attempt to apply and hold the specified amount of vacuum using the hand held vacuum pump J 23738-A .
  9. Command the EVAP Vent Valve OFF (open) while monitoring the hand held vacuum pump gauge.

Does the vacuum drop from the specified value when the EVAP Vent Valve is opened?

5 in Hg

Go to Step 8

Go to Step 6

6
  1. Leave the system as connected in step 4.
  2. Disconnect the vent line at the EVAP Vent Valve.
  3. Plug the vent line.
  4. Attempt to apply and hold the specified amount of vacuum using the hand held vacuum pump J 23738-A .
  5. Remove the plug from the vent line while monitoring the hand held vacuum pump gauge.

Does the vacuum drop from the specified value when the vent line is unplugged?

5 in Hg

Go to Step 10

Go to Step 7

7
  1. Inspect the EVAP Vent line from the canister to the EVAP Vent Valve for restrictions.
  2. Repair as necessary if you find a condition.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

8
  1. Test the fuel tank vapor line for a restriction.
  2. Repair as necessary if you find a condition.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 9

9

Important: The following steps require the EVAP pressure/purge diagnostic station J 41413 .

Always zero the EVAP Pressure and Vacuum (in. H2O) gauges on the EVAP pressure/purge diagnostic station before proceeding with diagnosis. Refer to the users guide.

  1. Turn OFF the ignition.
  2. Remove the plug and the hand held vacuum pump.
  3. Reconnect the EVAP vapor canister purge and vent lines.
  4. Connect the EVAP pressure/purge diagnostic station to the EVAP system service port.
  5. Operate the vehicle until the EVAP Purge Solenoid Valve can be commanded ON with a scan tool.
  6. Command the EVAP Purge Solenoid Valve ON with the engine running and quickly SEAL the system with the scan tool.

    7. Important: Refer to test description for further information.

  7. Compare the EVAP pressure/purge diagnostic station's vacuum gauge (in. H2O) to the vacuum shown on the scan tool from the Fuel Tank Pressure sensor while the system is sealed.

Does the Fuel Tank Pressure sensor indicate the actual amount of vacuum in the EVAP system?

--

Go to Step 3

Go to Step 12

10

Replace the EVAP Vent Valve. Refer to Evaporative Emission Vent Valve Replacement .

Is the action complete?

--

Go to Step 13

--

11

Replace the EVAP Vapor Canister. Refer to Evaporative Emission Canister Replacement .

Is the action complete?

--

Go to Step 13

--

12

Replace the Fuel Tank Pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement .

Is the action complete?

--

Go to Step 13

--

13
  1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
  2. Idle the engine at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 14

Go to Step 2

14

Select the Capture Info option and the Review Info option using the scan tool.

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

--

Go to the applicable DTC table

System OK