Circuit Description
The PCM tests the EVAP system for the following conditions:
| • | Large and small leaks |
| • | Excess vacuum |
| • | Purge flow during non-commanded conditions |
| • | Fuel Level and Fuel Pressure sensor faults |
| • | EVAP Purge and Vent Valve faults |
The PCM monitors the amount of vacuum in the EVAP system by monitoring the Fuel Tank Pressure sensor. The PCM commands the EVAP Purge Valve OFF and the EVAP Vent Valve ON when the Test Conditions have been met. This test indicates a leaking EVAP Purge Valve or FLOW DURING NON-PURGE if the Fuel Tank Pressure sensor indicates increasing fuel tank vacuum. This DTC will set after twice failing the above test.
Conditions for Running the DTC
| • | EVAP Vent Valve ON (closed) |
| • | EVAP Purge Solenoid Valve OFF (closed). |
Conditions for Setting the DTC
An increasing vacuum in the EVAP system is monitored.
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Diagnostic Aids
Perform a physical inspection of the EVAP system. Check for the following conditions:
| • | Incorrectly routed or defective EVAP system vacuum and vapor lines. |
| • | A stuck open EVAP Purge Valve. |
| • | A malfunctioning or damaged vapor canister |
Check for charcoal release from the vapor canister. Refer to the EVAP System Cleaning procedure.
Test Description
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the vacuum gauge ever indicate vacuum? | -- | Fault not present. Refer to Diagnostic Aids | ||
3 |
Important: Check for carbon contamination. Refer to Diagnostic Aids. Replace the EVAP Purge Solenoid Valve. Go to Evaporative Emission Canister Purge Solenoid Valve Replacement for replacement procedures. Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
