P1442
DTC P1442 EVAP Vacuum Switch Circuit:
DTC P1442 EVAP Vacuum Switch Circuit (continued):
EVAP System Circuit:
CIRCUIT DESCRIPTION
The EVAP purge vacuum switch is a normally closed switch positioned in the purge line between the canister and the Evaporative Emissions (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. If the EVAP switch signal circuit is open when vacuum sufficient to open the EVAP vacuum switch should not be present, DTC P1442 will set.
CONDITIONS FOR SETTING THE DTC
^ No active Throttle Position (TP) sensor, Intake Air Temperature (IAT) sensor, Manifold Absolute Pressure (MAP) sensor, Engine Coolant Temperature (ECT) sensor or Mass Air Flow (MAF) sensor DTC(s) set.
^ Intake Air Temperature is between 0°C (32°F). and 70°C (158°F).
^ The EVAP purge vacuum switch is open during key ON (before the engine is cranked).
ACTION TAKEN WHEN THE DTC SETS
^ he PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The history DTC will clear afier 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC 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 wiring 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.
^ Restricted fuel vapor line, purge hose, canister vent, or blocked canister. A condition that causes the EVAP system to trap vacuum can keep the EVAP vacuum switch open, causing DTC P1442 to be set. Refer to EVAP Control System. System Diagnosis - EVAP Control
^ Faulty or damaged canister. A faulty canister may intermittently allow charcoal into the EVAP purge solenoid, vacuum switch, and associated lines causing a DTC to be set. Replace the EVAP Canister. Refer to EVAP Canister.
Reviewing the Fail 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 Table.
2. The EVAP vacuum switch is normally closed when no vacuum is present. With the key ON and the engine not running, there shouldn't be any vacuum 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.
7. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.