System Description
The evaporative system includes the following components:
| • | The fuel tank |
| • | The EVAP vent solenoid |
| • | The fuel tank pressure sensor |
| • | The fuel pipes and the hoses |
| • | The fuel vapor lines |
| • | The fuel cap |
| • | The EVAP canister |
| • | The purge lines |
| • | The EVAP canister purge valve |
| • | The EVAP service port |
The evaporative emission system is checked by applying vacuum to the EVAP system and by monitoring for a vacuum decay. The PCM monitors the vacuum level through the fuel tank pressure 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.
The EVAP canister purge valve allows the manifold vacuum to purge the canister. The Powertrain Control Module (PCM) supplies a ground in order to energize the solenoid valve (purge ON). The EVAP canister purge valve control is Pulse Width Modulated (PWM) or turned ON and OFF several times per second. The duty cycle (pulse width) is determined by the engine operating conditions including the load, the throttle position, the coolant temperature and the ambient temperature. The duty cycle is calculated by the PCM and the output is commanded when the appropriate conditions have been met.
The system checks for conditions that cause the EVAP system to purge continuously by commanding the EVAP vent solenoid ON and the EVAP canister purge valve OFF (EVAP vent solenoid CLOSED, EVAP purge PWM 0 percent). If the fuel tank vacuum level increases during the test, a continuous purge flow condition is indicated. This can be caused by the following conditions:
| • | A leak in the EVAP canister purge valve |
| • | The EVAP purge and engine vacuum lines may be switched at the EVAP canister purge valve |
| • | The EVAP canister purge valve driver circuit is grounded |
If any of these conditions are present, DTC P1441 will set.
Conditions for Setting the DTC
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134 and P1133 are not set. |
| • | The BARO is greater than 75 kPa. |
| • | The intake air temperature is between 5°C and 29°C (41°F and 84°F) at engine start up. |
| • | The engine coolant temperature is between 5°C and 29°C (41°F and 84°F) at engine start up. |
| • | The Intake Air Temperature is not more than 1°C (2°F) greater than the Engine Coolant Temperature at start up. |
| • | The Engine Coolant Temperature is not more than 7°C (12°F) greater than the Intake Air Temperature at start up. |
| • | The fuel tank level is between 26 percent and 74 percent. |
| • | The TP sensor is between 9 percent and 35 percent. |
| • | The EVAP solenoid is at 50 percent PWM within 65 seconds of the engine run time. |
| • | A continuous purge flow condition is detected during the diagnostic test. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) illuminates. |
| • | The PCM records the operating conditions at the time when the diagnostic fails. This information stores in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three 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. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
Although this DTC is considered a type A diagnostic (refer to Powertrain Control Module (Serial Data Communication) ), this DTC acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports that the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure does not report to the diagnostic executive or display on a scan tool. A passing system always reports to the diagnostic executive immediately.
Check for the following conditions:
| • | Poor connection at PCM. Inspect harness connectors for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed connectors |
| - | Damaged terminals |
| - | Poor terminal to wire connection |
| • | A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, connect the EVAP pressure/purge cart J 41413 to the EVAP service port, pressurize the EVAP system to 10 in. H2O and observe the Fuel Tank Vacuum Pressure display on the scan tool while moving the connectors and the wiring harnesses related to the EVAP canister purge valve. A sudden change in the display will indicate the location of the fault. |
| • | An incorrect vacuum line routing. Verify that the source vacuum line routing to the EVAP canister purge valve is correct and that the EVAP purge and the source vacuum lines to the EVAP canister purge valve are not switched. |
| • | Loose Carbon in the purge solenoid. Blow out the lines and replace the purge canister. Refer to Carbon Particle Removal from Evaporative Emission System for a further procedure. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.
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If an EVAP canister purge valve electrical fault is present, the purge system will not operate correctly. Repairing the electrical fault will very likely correct the condition that set DTC P1441.
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Checks the fuel tank vacuum sensor at ambient pressure.
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Forces the fuel tank pressure sensor to re-zero.
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Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
-
If the EVAP purge and engine vacuum lines are switched at the EVAP canister purge valve, the solenoid valve will leak vacuum.
-
Duplicates the On-Board Diagnostic test.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Does the purge valve and vent solenoid click when command ON and OFF? | -- | |||
Is the Fuel Tank Pressure at the specified value? | 0 in. H2O (± 1 in. H2O) | |||
4 | Has the battery been disconnected? | -- | ||
Disconnect the battery. Is the action complete? | -- | -- | ||
6 |
Important:: Before continuing with the diagnosis, zero the EVAP Pressure and Vacuum gauges on the EVAP pressure/purge cart J 41413. Also read the temperature variatiod (refer to tool operating instructions).
Can the specified value be achieved? | 5 in H2O | ||
Is the Fuel Tank Pressure at the specified value? | 5 in. H2O ( ± 2 in. H20) | |||
8 |
Does the EVAP canister purge valve maintain vacuum at the specified value? | 15 in. Hg | ||
Check the EVAP purge and source vacuum line routing and connections at the EVAP canister purge valve. Are the EVAP purge and source vacuum lines connected correctly at the EVAP canister purge valve? | -- | Refer to Diagnostic Aids | ||
10 | Replace the EVAP canister purge valve. Refer to Diagnostic Aids . Is the action complete? | -- | -- | |
11 | Correct the EVAP purge and source vacuum line routing and connections. Is the action complete? | -- | -- | |
Does the Fuel Tank Pressure remain at or above the specified value while the EVAP vent solenoid is command ON (closed) and the EVAP canister purge valve is command OFF (0%)? | 0 in. H2O 2500 RPM | System OK |
