Circuit Description
The evaporative emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum decay. The PCM monitors the vacuum level through the fuel tank vacuum sensor signal. At an appropriate time, the EVAP canister purge 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 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 valve (EVAP vent solenoid "Open," EVAP purge PWM "0%") and monitoring the fuel tank vacuum sensor input. With the EVAP vent solenoid open, any vacuum in the system should decrease quickly unless the vent path is blocked.
Conditions for Setting the DTC
| • | The BARO is greater than 75 kPa |
| • | The intake air temperature is between 4° C and 30° C at engine start up. |
| • | The engine coolant temperature is between 4° C and 30° C at engine start up |
| • | The ECT sensor and IAT sensor are within 1° C (2° F) of each other at engine start up. |
| • | The start-up ECT is less than 7° C (12° F) than the start-up IAT. |
| • | Fuel tank level is between 40 % and 90 % |
| • | The TP sensor is between 9 and 35 % |
| • | The EVAP purge solenoid is at 50% PWM within 65 seconds after engine start. |
| • | One or more of the following DTCs are not set P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134 and P1133. |
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. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The malfunction indicator lamp (MIL) will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at 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 solenoid and the fuel tank pressure sensor for an intermittent open or short circuit. |
| • | Kinked, pinched or plugged vent hose: Verify that the vent hose between the canister and the EVAP vent solenoid is not restricted. |
Check for charcoal particles. Refer to Carbon Particle Removal from EVAP System before starting repairs.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that causes the DTC to be set occurs. This may assist in diagnosing the condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure Records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurs. Refer to this information on the scan tool later.
-
Whenever a vent solenoid electrical fault is present, the purge system will not operate correctly. Repairing the electrical fault will very likely correct the condition that set DTC P0446.
-
Checks the fuel tank vacuum sensor at ambient pressure.
-
Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
-
Checks for a blocked EVAP canister.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
2 | Is DTC P0460 also set? | -- | ||
Does the purge valve and vent solenoid click when commanded ON and OFF? | -- | |||
Is the fuel tank pressure at the specified value? | 0 in. H2O (±1 in. H2O) | |||
5 | Has the battery been disconnected? | -- | ||
6 | Disconnect the battery. Is the action complete? | -- | -- | |
7 |
Important: Before continuing with the diagnosis, zero the EVAP pressure and vacuum gauges on the EVAP pressure/purge cart. Also review the temperature variation instruction included with J 41413 before perfoming this step. Enhanced EVAP Pressure Purge Diagnostic Cart . Refer to the tool operating instructions.
Is the Fuel Tank Pressure at the specified value? | 5 in. H2O 5 in. H2O ( ±2 in. H2O) | ||
Does the EVAP pressure return to the specified value within 5 seconds? | 5 in. H2O 0 in. H2O | Go to Diagnostic Aids | ||
Does the vacuum remain below the specified value? | 5 seconds 2500 RPM 30 in. H2O | |||
10 |
Was a problem found? | -- | ||
11 | Replace the EVAP vent valve. Refer to Diagnostic Aids. Refer to EVAP Vent Valve Replacement . Is the action complete? | -- | -- | |
12 | Replace the EVAP canister. Refer to Diagnostic Aids. Refer to EVAP Canister Replacement . Is the action complete? | -- | -- | |
13 |
Switch the rotary switch on the cart Enhanced EVAP Pressure Purge Diagnostic Cart to HOLD. Does the EVAP pressure return to the specified value within 5 seconds? | 5 in. H2O 0 in. H2O | System OK |
