GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Firebird 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Evaporative Emission Control System Diagnosis

Refer to

EVAP Control System Overview


Object Number: 200517 Size: LF
(1)EVAP Vent Valve/Solenoid
(2)EVAP Vent Valve/Solenoid Ignition Feed Circuit Terminal
(3)EVAP Vent Valve/Solenoid Control Circuit Terminal
(4)EVAP Vent Valve/Solenoid Filter
(5)EVAP Vapor Lines
(6)Fuel Tank Pressure Sensor
(7)Fuel Tank Pressure Sensor Ground Circuit Terminal
(8)Fuel Tank Pressure Sensor Signal Circuit Terminal
(9)Fuel Tank Pressure Sensor Circuit 5 Volt Reference Circuit Terminal
(10)Fuel Filler Pipe
(11)Check Valve (Spitback)
(12)Modular Fuel Sender Assembly
(13)Fuel Limiter Vent Valve (FLVV)
(14)Pressure/Vacuum Relief Valve (Optional)
(15)EVAP Canister
(16)EVAP Canister Purge Valve/Solenoid Ignition Feed Circuit Terminal
(17)EVAP Canister Purge Valve/Solenoid Control Circuit Terminal
(18)Intake Manifold Vacuum Source
(19)EVAP Canister Purge Valve/Solenoid
(20)EVAP Service Port
.

System Description

The EVAP canister purge valve allows manifold vacuum to purge the canister. The powertrain control module (PCM) supplies a ground to energize the purge valve (purge ON). The EVAP purge valve control is pulse width modulated (PWM) or Turned ON and OFF several times a second. The duty cycle (pulse width) is determined by engine operating conditions including load, throttle position, coolant temperature and ambient temperature. The duty cycle is calculated by the PCM and the output is commanded when the appropriate conditions have been met.

The EVAP Vent valve is used to seal the EVAP system during diagnostic tests. The fuel tank pressure sensor is used to monitor vacuum in the system during the diagnostic tests.

A stuck closed EVAP canister purge valve, Stuck open EVAP vent valve, disconnected or damaged EVAP Purge line or vent hose, leaking fuel cap, or fill neck should set a DTC P0440. A small leak in the EVAP system should set a DTC P0442 An EVAP vent valve stuck closed, a restricted vent hose, or a blocked EVAP canister should set a DTC P0446. A continuous purge condition with no purge commanded by the PCM (EVAP purge valve stuck open or leaking) should set a DTC P1441. Refer to the DTC tables for further diagnostic procedures regarding the EVAP system.

Diagnostic Aids

Check for the following conditions:

    •  Cracked or punctured EVAP canister
    •  Damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
    •  Poor connection at the PCM
    •  Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
    •  Damaged harness. Inspect the wiring harness to the EVAP vent valve, the EVAP purge valve, and the fuel tank pressure sensor for an intermittent open or short circuit.
    •  Kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted.
    • Use the following procedure to check for a carbon release condition that could plug the system.
        1.  Turn OFF the ignition.
        2.  Remove the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .
        3.  Lightly tap the canister purge valve on a clean work area looking for carbon particles exiting either of the vacuum ports.
        4.  If no carbon release is evident, reinstall the components and continue with the DTC P0440 diagnostic table. If carbon is being released from either component, continue with this service procedure.
        5.  Remove the charcoal canister from the vehicle.
        6.  Ensure that the main cylinder valve is turned off on the
Object Number: 20803 Size: SH
(1)Main Valve
(2)Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3)Nitrogen Cylinder
(4)Black Connecting Hose
(5)Threaded Fitting
(6)Gauge Set
EVAP purge/pressure diagnostic station.
        7.  Disconnect the black hose that connects the nitrogen cylinder to the
Object Number: 20803 Size: SH
(1)Main Valve
(2)Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3)Nitrogen Cylinder
(4)Black Connecting Hose
(5)Threaded Fitting
(6)Gauge Set
EVAP purge/pressure diagnostic station at the pressure regulator by unscrewing the knurled nut on the regulator. No tools are required to remove the black hose from the regulator.
        8.  Using a section of vacuum line, connect one end over the open threaded fitting of the EVAP purge/pressure diagnostic station pressure regulator.
        9.  Connect the remaining end to the purge valve end of the EVAP purge line at the vehicle and turn on the main nitrogen cylinder valve. Continue to blow any debris from the purge line for 15 seconds.
        10.  Return the
Object Number: 20803 Size: SH
(1)Main Valve
(2)Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3)Nitrogen Cylinder
(4)Black Connecting Hose
(5)Threaded Fitting
(6)Gauge Set
EVAP pressure/purge diagnostic station to its original condition by reinstalling the black hose that was disconnected in step 7.
        11.  Replace the following components:
   •  The EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .
   •  The EVAP canister. Refer to Evaporative Emission Canister Replacement .

Test Description

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

  1. The Powertrain On-Board Diagnostic (OBD) System Check prompts you to complete some of the basic checks and store the Freeze Frame and Failure Records Data on the scan tool if applicable.

    2.

  2. If a vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the DTC to set will very likely correct the condition.

    3.

  3. Inspects for a fuel tank pressure sensor stuck high condition. The fuel tank pressure must be relieved by removing the canister line from the purge valve. The fuel fill cap will not relieve the fuel tank pressure due to a check valve in the filler neck. The check valve seals when pressure is applied to prevent vapors from escaping through the filler neck. The scan tool should read within 1.0 inch H2O of the specified value.

    4.

  4. Inspects for a large leak in the EVAP system.

    5.

  5. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. The EVAP station is pressurizing a sensor that normally reads vacuum. The scan tool reads high pressure at 0 volts and high vacuum at 5 volts. the scan tool can only read a max pressure of 6.0 inches of H2O (0 volts). However the EVAP service station can pressurize the system to much higher pressures. The scan tool value should be within 0.5 of the specified value.

    6.

  6. Inspects for a stuck closed EVAP vent valve. The value should decrease to within 1.0 in Hg of the specified value.

    7.

  7. Inspects for a leaking or stuck open EVAP canister purge valve. The scan tool should read within 1.0 inch HG of the specified value.

    8.

  8. Ensures that sufficient source vacuum is present at the EVAP canister purge valve/solenoid.

    9.

  9. Inspects for a small leak in the EVAP system.

EVAP Control System Diagnosis

Step

Action

Values

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

Important: Visually/Physically inspect for the following conditions:

    • Vacuum or purge lines disconnected. Refer to Emission Hose Routing Diagram .
    • Loose or missing fuel fill cap.

Did DTC P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit or DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit also set?

--

Go to applicable DTC

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the canister purge line from the EVAP canister purge valve.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the fuel tank pressure parameter.

Does the scan tool indicate fuel tank pressure near the specified value?

0 in H2O

Go to Step 4

Go to Step 9

4

Important: Before continuing with diagnosis, zero the EVAP pressure and vacuum (inches of H2O) Gauges on the J 41413 EVAP pressure/seal diagnostic station.

  1. Turn OFF the ignition.
  2. Reconnect all EVAP hardware that was previously disconnected.
  3. Install theJ 41415-40 fuel tank cap adapter to the fuel fill neck and fuel fill cap.
  4. Connect the EVAP station to the fuel tank cap adaptor.
  5. Turn ON the ignition, with the engine OFF.
  6. With a scan tool, capture Fail Record data for DTC P0440 and clear DTCs.
  7. With a scan tool, command the vent valve ON (closed) to seal the system.

    8. Important: Do not exceed the pressure in the specified value.

  8. With the EVAP station, attempt to pressurize the system to the specified value by slowly turning the rotary switch to the PRESSURE position. Monitor the pressure with the gauge on the EVAP station with the rotary switch in the OFF/HOLD position.

Did you achieve the specified value?

5 in. H2O

Go to Step 5

Go to DTC P0440 Evaporative Emission (EVAP) System

5

  1. With the EVAP station, maintain the fuel tank pressure at the specified value. Monitor the pressure with the gauge on the cart with the rotary switch in the OFF/HOLD position.
  2. With a scan tool, observe the fuel tank pressure parameter.

Does the scan tool indicate fuel tank pressure near the specified value?

5 in H2O

Go to Step 6

Go to Step 11

6

With a scan tool, command the vent valve OFF (open) to relieve the pressure.

Does the pressure decrease to near the specified value within 2 minutes with the rotary switch in the OFF/HOLD position?

5 in. H2O

Go to Step 7

Go to DTC P0446 Evaporative Emission (EVAP) Vent System Performance

7

  1. Connect the inch Hg vacuum hose on the EVAP station to the canister side of the purge valve.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, select the Seal option to seal the EVAP system.
  4. Start the engine.
  5. Run the engine from 1200-1500 RPM and observe vacuum level.

Does the vacuum level measure above the specified value?

0 in. Hg

Go to Step 8

Go to Step 12

8

  1. With a scan tool, increase purge to 100 percent.
  2. Run the engine from 1200-1500 RPM and observe vacuum level.

Does the vacuum level measure above the specified value?

15 in. Hg

Go to Step 14

Go to Step 13

9
  1. Turn OFF the ignition.
  2. Disconnect the EVAP canister line from the fuel tank or EVAP canister.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe Fuel Tank Pressure Parameter .

Does the scan tool indicate fuel tank pressure near the specified value?

0 in H2O

Go to Step 10

Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

10

Check for a kinked or restricted canister purge line between the EVAP canister purge valve and EVAP canister.

Did you find and correct the condition?

0 in. H2O

Go to Step 14

--

11

Visually/Physically inspect for the following conditions:

    • Restricted fuel tank vapor line.
    • Restricted EVAP purge line.

Did you find and correct the condition?

--

Go to Step 14

Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

12

Check for no source vacuum to the EVAP purge valve.

Did you find and correct the condition?

--

Go to Step 14

--

13

Important: Check for carbon release into the EVAP system. Refer to Diagnostic Aids.

Locate and repair cause of no source vacuum to the EVAP purge valve.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

14

  1. Reconnect all EVAP hardware that was previously disconnected.
  2. Turn ON the ignition , with the engine OFF.
  3. With scan tool, select the Seal option to seal the EVAP system.

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

  4. With the EVAP station, pressurize the system to the first specified (higher) value by slowly turning the rotary switch to the PRESSURE position. Monitor the pressure with the gauge on the cart with the rotary switch in the OFF/HOLD position.

Does the EVAP pressure decrease to less than the second specified (lower) value within 2 minutes with the rotary switch in the OFF/HOLD position?

15 in H2O

10 in H2O

Go to DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected

System OK