Refer to Emission Hose Routing Diagram,
EVAP Control System Overview
EVAP System Operation
A RESTRICTED or BLOCKED EVAP VENT PATH is detected by monitoring fuel tank pressure during normal operation (EVAP vent valve/solenoid open, EVAP purge valve/solenoid normal). With the EVAP vent valve/solenoid open, vacuum level in the system should be very low unless the vent path is blocked. A blockage can be caused by the following conditions:
| • | Faulty EVAP vent valve/solenoid (stuck closed). |
| • | Plugged kinked or pinched vent hose. |
| • | Shorted EVAP vent valve/solenoid driver circuit. |
| • | Plugged EVAP canister. |
If any of the conditions described above are present, DTC P0446 will set.
Conditions for Running the DTC
| • | No TP sensor, ODM, IAT sensor, or MAP sensor DTCs set. |
| • | All conditions for P0440 and P0442 have been met and passed. |
| • | Startup engine coolant temperature is not more than 4°C and 30°C (40°F 86°F). |
| • | Startup engine is not more than 8°C (14° F). |
| • | Startup Intake air temperature not more than 2°C and 30°C (40°F and 86°F). |
| • | Startup intake air temperature not more than 2°C (4°F). |
| • | Fuel tank level is between 15% and 85%. |
| • | BARO is greater than 75kPa. |
Conditions for Setting the DTC
| • | Fuel tank pressure is less than -10 in. H2O. |
| • | The condition is present for up to 30 seconds. |
Action Taken When the DTC Sets
Important: Although these diagnostics are considered type A, they act like type B diagnostics under certain conditions. Whenever the EVAP diagnostics report that a system has passed, or if the battery has been disconnected, the diagnostic must fail during 2 consecuitive cold start trips before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.
| • | The PCM will illuminate the MIL during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Check for the following conditions:
| • | Kinked, pinched or plugged vent hose. |
| • | Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
-
The power train OBD System Check promps you to the basic checks and store the freeze frame and failure records data on the Scan Tool if applicable.
-
If a EVAP vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the additional DTC to set will very likely correct the condition that set this DTC.
-
Checks for a fuel tank pressure sensor stuck high condition. The fuel tank pressure must be relieved by removing the canister line from the fuel tank or EVAP canister. The fuel fill cap will not relieve the tank pressure due to a check valve in the filler neck. The check valve seals when pressure is applied to prevent vapor from escaping through the filler neck. The scan tool should read within +/- 1.0 in. H2O of the specified value.
-
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 Tech II can only read a max pressure of 6.0 in. 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.
-
Checks for a plugged or stuck closed EVAP Vent Valve/Solenoid. The value should decrease to within +/- 1.0 in. HG of the specified value.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Did you preform the Powertrain On Board Diagnostic (OBD) System Check? | -- | |||||||
|
Important: Visually/Physically inspect for the following conditions:
Is DTC DTC P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit or DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit also set? | -- | Go to the other DTC first | ||||||
Is Fuel Tank Pressure near the specified value? | 0 in. H2O | |||||||
|
Important: : Before continuing with diagnosis, zero the EVAP Pressure and Vacuum (inches of H2O gauges on the J 41413 EVAP Pressure/Purge Diagnostic Station. Important: Do not exceed the pressure in the specified value.
Is the Fuel Tank Pressure at the specified value? | 5 in. H2O | |||||||
Does the EVAP pressure gauge decrease to near the Second specified (lower) value within 2 minutes with the rotary switch in the "Off/Hold" position? | 5 in. H2O 0 in. H2O | Go to Diagnostic Aids | ||||||
6 |
Does the vacuum remain below than the specified value? | 10 in. H2O | ||||||
7 |
Was a problem found? | -- | ||||||
8 |
Is the action complete? | -- | -- | |||||
9 |
Is the action complete? | -- | -- | |||||
10 |
Is action complete? | 0 in. H2O | -- | |||||
11 |
Is Fuel Tank Pressure near the specified value? | 0 in. H2O | Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage | |||||
12 |
Does EVAP pressure decrease to less than the second specified (lower) value within 2 minutes with the rotary switch in the 'Off/Hold" position? | 5 in. H2O 0 in. H2O | System OK |
