Circuit Description
The PCM tests the EVAP system for the following conditions:
| • | Large and small leaks (P0440 and P0442) |
| • | Excess vacuum (P0446) |
| • | Purge flow during non-commanded conditions (P1441) |
| • | Fuel Pressure sensor and Fuel Level sensor faults (P0452, P0453, P0461, P0462 and P0463) |
| • | EVAP Purge and Vent Valve faults (P1645 and P1646) |
The PCM monitors the amount of vacuum and the amount of pressure in the EVAP system by monitoring the Fuel Tank Pressure sensor. For this DTC the PCM turns ON both the EVAP Purge Valve and the EVAP Vent Valve when the Conditions for Running the DTC are met. This applies an engine vacuum to a closed EVAP system. The PCM turns OFF both the EVAP Purge Valve and the EVAP Vent Valve when the system reaches a correct amount of vacuum. The EVAP system should quickly RELEASE the vacuum in the EVAP system with the EVAP Purge Valve OFF and the EVAP Vent Valve OFF (open). This test indicates a blocked or restricted EVAP Vent Valve or path if the EVAP system fails to release the vacuum quickly enough. This DTC will set after two consecutive failures of the above test.
Conditions for Running the DTC
| • | DTC's P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0141, P0151, P0152, P0153, P0154, P0452, P0453, P0503, P1111, P1112, P1114, P1115, P1133 or P1153 are not set. |
| • | Battery voltage is between 10.5 and 17.5 volts. |
| • | Barometric pressure is more than 71.78 kPa. |
| • | Fuel level is between 10% and 89.8% of full capacity for at least 3.2 seconds continuously. The time limit is required because fuel sloshing within the tank may cause the fuel level indication to vary outside the fuel level limits. |
| • | Coolant temperature is between 2°C and 32.7°C. |
| • | Intake air temperature is between 2°C and 32.7°C |
| • | Start up coolant and intake air temperature are within 14.2°C of each other. |
Conditions for Setting the DTC
| • | The EVAP system fails to vent vacuum at a quick enough rate. |
| OR |
| • | There is too much system vacuum present at the start of this test. |
Important: This DTC does NOT report a first failed test. A first fail of this DTC will have a scan tool status as Not Run. Use the scan tool data display parameter of EVAP TEST RESULT to determine if this DTC has failed or passed for THIS ignition cycle.
Action Taken When the DTC Sets
| • | The PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive drive trips that the diagnostic runs and fails. |
| • | The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Freeze Frame and Failure Records. |
| • | A first failure of this DTC will NOT store as Last Test Failed or History. |
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 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 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
Important: An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose fuel level sensor DTC's before performing this DTC's diagnostic table. Always check for fuel level sensor DTC's stored as History.
Perform a physical inspection of the EVAP system. Check for the following conditions:
| • | A loose, missing, defective, or incorrect fuel tank cap |
| • | Incorrectly routed or defective EVAP system vacuum and vapor lines |
| • | A stuck closed EVAP Vent Valve |
| • | A restricted or blocked EVAP system hose |
| • | A restricted or stuck closed fuel tank rollover valves |
| • | A malfunctioning or damaged vapor canister |
Check for charcoal release from the vapor canister. Refer to Evaporative Emission System Cleaning .
If the vehicle had a P1441 stored and set a P0446 while performing the Service Bay Test inspect the EVAP Solenoid Purge Valve for Flow During Non-Purge (leakage).
The vacuum and pressure in the EVAP system is measured in inches of water (H2O). Most gauges measure vacuum in inches of mercury (Hg) and pressure in pounds per square inch (psi). The following shows how the values compare:
in H2O | in Hg | psi |
|---|---|---|
1in H2O | 0.07 in Hg | 0.0361 psi |
5 in H2O | 0.36 in Hg | 0.180 psi |
10 in H2O | 0.73 in Hg | 0.361 psi |
15 in H2O | 1.10 in Hg | 0.541 psi |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
If the vacuum stored in the EVAP system is quickly released then an intermittent system restriction or failure of the EVAP Vent Valve or the EVAP Fuel Tank Pressure Sensor may have occurred.
-
Checking the vapor canister and the EVAP Vent Valve for restriction.
-
An EVAP Pressure sensor that does not correctly respond to pressure (or vacuum) will cause this DTC to set.
The EVAP Pressure Sensor monitors a range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).
In order to test the EVAP Pressure sensor for pressure response SEAL the system with the scan tool and use the EVAP pressure/purge diagnostic cart to apply pressure to the system. Compare the pressure gauge (in. H2O) on the diagnostic cart to the EVAP Pressure sensor reading on the scan tool.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
2 |
Was a repair made to the EVAP system? | -- | ||||||
3 |
Is the value displayed the same or less than the value specified? | 0 in. H2O | ||||||
Does the EVAP Fuel Tank Pressure sensor drop to the specified value when 0% EVAP Purge is commanded and the EVAP Vent Valve is opened? | 0 in. H2O | Go to Test Description | ||||||
5 |
Does the vacuum drop from the specified value when the EVAP Vent Valve is opened? | 5 in. Hg. | ||||||
6 |
Does the vacuum drop from the specified value when the vent line is unplugged? | 5 in. Hg. | ||||||
7 |
Was the EVAP Vent line replaced? | -- | ||||||
8 |
Was the fuel tank vapor line replaced? | -- | ||||||
9 |
Important: The following steps require the EVAP pressure/purge diagnostic station J 41413. Always zero the EVAP Pressure and Vacuum (in. H2O) gauges on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
Do both values indicate the same amount of vacuum in the EVAP system to within the range specified? | + or - 2 in. H2O | ||||||
10 |
Is the resistance the same or less than the value specified? | 5 ohms | ||||||
11 | Replace the EVAP Vent Valve. Is the replacement complete? | -- | -- | |||||
12 | Replace the EVAP Vapor Canister. Is the replacement complete? | -- | -- | |||||
13 | Replace the EVAP Fuel Tank Pressure sensor. Is the replacement complete? | -- | -- | |||||
14 | Repair the open EVAP Fuel Tank Pressure sensor ground circuit. Is the repair complete? | -- | -- |
