P1442

Circuit Description
Canister purge is controlled by a solenoid valve that allows manifold vacuum to purge the canister. The powertrain control module (PCM) supplies a ground to energize the solenoid valve (purge "ON"). The EVAP purge solenoid 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 EVAP purge vacuum switch is a normally closed switch positioned in the purge line between the canister and the EVAP purge solenoid. The EVAP purge vacuum switch will open when vacuum increases to greater than 5 inches of water in the purge line. The PCM monitors the EVAP purge vacuum switch signal to determine if the evaporative emission control system is working properly.

Conditions for Setting the DTC
- No active AT sensor, MAP sensor, ECT sensor or TP sensor start-up DTCs set.
- Ignition ON," engine"OFF," system voltage is between 11.5 volts and 16 volts.
- Start-up intake air temperature (IAT) and start-up engine coolant temperature (ECT) are both above 5°C (41°F).
- Start-up engine coolant temperature is below 50°C (122°F).
- The EVAP purge vacuum switch is open during ignition "ON" (before the engine is cranked) 4 times over the last 8 times the ignition was switched "ON.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) after the second consecutive trip in which DTC sets.
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL "OFF" on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P1442 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- DTC P1442 can be cleared by using the scan tool "Clear Info" function or by disconnecting the PCM battery feed.

Diagnostic Aids
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 wring harness for damage. If the harness appears to be OK, observe the EVAP vacuum switch display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
2. The canister purge vacuum switch is normally closed when no vacuum (purge) is present. With the key "ON" and the engine "OFF," there should not be any vacuum (purge) present in the EVAP system.
3. Determines if the PCM is able to control the EVAP purge solenoid valve.
4. Determines if the DTC will set under the conditions present when the DTC was originally stored. If not, the fault is intermittent.




Diagnostic Chart