Circuit Description
By applying the vacuum to the EVAP system and monitoring for a vacuum decay, check the evaporative emission system. The PCM monitors the vacuum level from 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.
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 purge valve (purge ON). The EVAP canister purge valve control is Pulse Width Modulated (PWM) or turned ON and OFF several times a 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 PCM calculates the duty cycle 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 %). 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:
| • | The EVAP canister purge valve leaking |
| • | The EVAP purge and engine vacuum lines switched at the EVAP canister purge valve |
| • | The EVAP canister purge valve driver circuit grounded |
If any of these conditions are present, the DTC P1441 will set.
Conditions for Setting the DTC
| • | The DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134 and P1133 not set. |
| • | The intake air temperature is above 0° C (32° F). |
| • | The fuel tank level is between 40 % and 90 %. |
| • | A continuous purge flow condition is detected during the diagnostic test. |
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
Although this DTC is considered a type A diagnostic (refer to Section 3), the DTC acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports the system has passed, or if the battery is disconnected, the diagnostic must fail twice 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.
Check for the following conditions:
| • | A poor connection at the PCM: Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and 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 Enhanced EVAP Pressure Purge Diagnostic Cart 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 source vacuum lines to the EVAP canister purge valve are not switched. |
Check for charcoal particles. Refer to Carbon Particle Removal from EVAP System before starting repairs.
Test Description
The numbers below refer to the step numbers 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 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.
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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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This step checks the fuel tank sensor at ambient pressure.
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This forces the PCM to zero the fuel tank pressure sensor.
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This step verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
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Verifys that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
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 commanded ON and OFF? | -- | |||
Is the Fuel Tank Pressure at the specified value? | 0 in. H2O (±1 in. H2O) | |||
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. Also review the temperature variation instructions included with J 41413 before performing this step.Enhanced EVAP Pressure Purge Diagnostic Cart .
Can the specified value be achieved? | 5 in. H2O | ||
Is the Fuel Tank Pressure at the specified value? | 5 in. H2O 5 in. H2O (±2 in. H2O) | |||
8 |
Does the EVAP canister purge valve maintain vacuum at the specified value? | 15 in. Hg | ||
9 | 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? | -- | Go to the Diagnostic Aids | |
10 | Replace the EVAP canister purge valve. Refer to Diagnostic Aids. Refer to Evaporative Emission Canister Purge Solenoid . Is the action complete? | -- | -- | |
11 | Correct the EVAP purge and source vacuum line routing and connections. Is the action complete? | -- | -- | |
12 |
Does the fuel tank vacuum pressure remain at or higher than the specified value? | 2500 RPM 0 in. H2O | System OK |
