Operation CHARM: Car repair manuals for everyone.
Home >> Isuzu Truck >> 1996 >> Hombre L4-2.2L CPC >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P1441

P1441

Evaporative Emission (EVAP) Control System:




System Description
The evaporative system includes the following components:
- Fuel tank
- EVAP vent solenoid
- Fuel tank vapor pressure sensor
- Fuel pipes and hoses
- Fuel vapor lines
- Fuel cap
- EVAP canister
- Purge lines
- EVAP canister purge valve

The evaporative emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum decay. The Powertrain Control Module (PCM) monitors the vacuum level through the fuel tank vacuum sensor signal. At an appropriate time, the Evaporative Emission (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 manifold vacuum to purge the canister. The PCM supplies a ground 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 a second. The duty cycle (pulse width) is determined by engine operating conditions including load, throttle position, coolant temperature and 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%"). If fuel tank vacuum level increases during the test, a continuous purge flow condition is indicated. This can be caused by the following conditions:
- EVAP canister purge valve leaking
- EVAP purge and engine vacuum lines switched at the EVAP canister purge valve
- EVAP canister purge valve driver circuit 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 not set.
- Intake air temperature is above O°C (32°F).
- Fuel tank level is between 15% and 85%.
- 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 operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

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 a up cycles without a fault.
- DTCs can be cleared by using a scan tool.

Diagnostic Aids

NOTE: Although this DTC is considered a type A diagnostic, 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:
- 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 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. H20 and observe the Fuel Tank Vacuum Pressure display on the scan tool while moving connectors and wiring harnesses related to the EVAP canister purge valve. A sudden change in the display will indicate the location of the fault.
- 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.

DTC P1441 - Evaporative Emission (EVAP) Control System Flow During Non-Purge (1 Of 2):




DTC P1441 - Evaporative Emission (EVAP) Control System Flow During Non-Purge (2 Of 2):




Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The OBD System Check prompts the technician to use the Capture Info. selection on the scan tool. This creates an electronic copy of the freeze frame data taken when the fault occurred. The information is then stored in the scan tool for reference.
2. 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.
3. Checks the fuel tank vacuum sensor at ambient pressure.
4. Checks for a stuck open EVAP canister purge valve.
5. Verifies that the fuel tank vapor pressure sensor accurately reacts to EVAP system pressure changes.
7. If the EVAP purge and engine vacuum lines are switched at the EVAP canister purge valve, the solenoid valve will leak vacuum.
pro multis · About Operation CHARM