GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Optra 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC P0456

Circuit Description

The evaporative emission (EVAP) small leak test applies vacuum to the EVAP system and monitors vacuum decay. The control module monitors the fuel tank pressure sensor signal to determine the vacuum decay rate. At an appropriate time, the EVAP canister purge valve and the EVAP vent valve are turned ON. This allows the engine to draw vacuum on the EVAP system. After the desired vacuum level has been achieved, the EVAP purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level during a given time period. If the system detects a leak larger than a calibrated amount, DTC P0456 will set.

DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC P0456 Evaporative Emission (EVAP) Very Small Leak Detected

Conditions for Running the DTC
    • Before the engine control module (ECM) can report DTC P0456 failed, DTC P0441 must run and pass.
    • DTCs P0106, P0107, P0108, P112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204 P0402, P0404, P0405, P0406, P0443, P0452, P0453, P0462, P0463, P0488, P0502, P2195, and P2196 are not set.
    • The ignition 1 voltage is between 11-16 volts.
    • The barometric pressure (BARO) is more than 72 kPa.
    • The engine coolant temperature (ECT) and the intake air temperature (IAT) at start-up are between -5 and +40°C (+23 and +140°F).
    • The engine is OFF for more than 6 hours or the following conditions must be met:
       - The start-up IAT minus start-up ECT are within 12°C (22°F).
       - The start-up ECT minus start-up IAT is within 50°C (90°F).
    • The start-up IAT minus IAT are within 3°C (5°F).
    • The purge enable time is less than 360 seconds.
    • The engine run time is more than 1 second and less than 360 seconds.
    • The fuel level is between 24-94 percent.
    • The engine speed is less than 1,200 RPM.
    • The vehicle speed is less than 3 km/h (2 mph).
    • The throttle position is less than 1 percent.
    • DTC P0456 runs once an ignition cycle when the above conditions are met.

Conditions for Setting the DTC

The EVAP system can achieve vacuum but a vacuum decay is detected 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

To help locate intermittent leaks, use the J 41413-200 Evaporative Emission System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15-second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step verifies that repairs are complete and that other conditions are not present.

Step

Action

Values

Yes

No

Schematic Reference: Evaporative Emissions Hose Routing Diagram

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, P0449, P0452, or P0453 are also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Inspect the evaporative emission (EVAP) system for the following conditions:
    2. • Loose, missing, or damaged service port 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 5

Go to Step 4

4

Important: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. The system flow will be less with higher temperatures.

  1. Turn OFF the ignition.
  2. Connect the J 41413-200 Evaporative Emission System Tester (EEST) power supply clips to a known good 12-volt source.
  3. Install the GE-41415-50 Fuel Tank Cap Adapter to the fuel fill pipe.
  4. Connect the J 41413-200 Nitrogen/Smoke Supply Hose to the GE-41415-50 .
  5. Turn ON the ignition, with the engine OFF.
  6. Turn the nitrogen/smoke valve on the J 41413-200 control panel to SMOKE.
  7. Command the EVAP vent solenoid closed.
  8. Use the remote switch to introduce smoke into the EVAP system.
  9. Use the J 41413-VLV EVAP Port Vent Fitting tool to open the EVAP service port.
  10. Remove the J 41413-VLV once the smoke is observed.
  11. Continue to introduce smoke into the EVAP system for an additional 60 seconds.
  12. Inspect the entire EVAP system for exiting smoke with the J 41413-SPT High Intensity White Light.
  13. Continue to introduce smoke at 15-second intervals until the leak source has been located.

Did you locate and repair a leak source?

--

Go to Step 5

Go to Diagnostic Aids

5

Important: Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.

  1. Turn the nitrogen/smoke valve to nitrogen.
  2. Connect the nitrogen/smoke hose to the 0.5 mm (0.020 in) test orifice on the bottom-front of the J 41413-200 .
  3. Use the remote switch to activate the J 41413-200 .
  4. Align the red flag on the flow meter with the floating indicator. Use the remote switch to de-activate the J 41413-200 .
  5. Install the GE-41415-50 to the fuel fill pipe.
  6. Remove the nitrogen/smoke hose from the test orifice and install the hose onto the GE-41415-50 .
  7. Turn ON the ignition, with the engine OFF.
  8. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating indicator stabilizes.
  9. Compare the flow meter stable floating indicator position to the red flag.

Is the floating indicator below the red flag?

--

Go to Step 6

Go to Step 2

6

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK