Circuit Description
This diagnostic test is used to determine if the Evaporative Emission (EVAP) control solenoid is open (passing vacuum) when the PCM is commanding it closed or if the EVAP vacuum switch or circuit is open. The Evaporative Emission (EVAP) vacuum switch is a normally closed switch mounted in the vacuum line between the EVAP canister and the EVAP solenoid. The switch opens when vacuum, 7.5 inches of water, from the engine draws the evaporative emissions from the EVAP canister through the EVAP solenoid and into the throttle body. The PCM monitors the state of the EVAP vacuum switch to determine if the EVAP solenoid is open and passing vacuum. The PCM accomplishes this by monitoring the amount of time the EVAP vacuum switch is continuously open or closed with purge off. If the switch is open during the test conditions for 9 consecutive seconds, DTC P1441 is set.
Conditions for Setting the DTC
Test Conditions
| • | DTCs P0101, P0102, P0103, P0107, P0108, P0122, P0123, P0401, P0506, P0507, P1508, P1509 and P1645 not set. |
| • | IAT at key ON is greater than -25°C (-13°F). |
| • | IAT remains below 99.5°C (211°F). |
| • | ECT at key ON is more than 10°C (50°F) less than previous key OFF ECT temperature. |
| • | ECT is less than 125°C (257°F). |
| • | MAP is between 2.2 kPa and 100 kPa. |
| • | Throttle position less than 81.6 degrees. |
| • | Engine speed between 500 and 6375 RPM. |
| • | EVAP solenoid duty cycle 9.8% or less but has been greater than 9.8% once this ignition cycle. |
Failure Condition
EVAP vacuum switch circuit open for 9 consecutive seconds.
Action Taken When the DTC Sets
| • | The PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive drive trips that the diagnostic runs and fails. |
| • | The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Freeze Frame and Failure Records. |
| • | A first failure of this DTC will store in Last Test Failed but not History. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A Last Test Failed DTC will clear when the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any diagnostic test. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Diagnostic Aids
Notice: Do not apply voltage to the EVAP vacuum switch. The voltage supplied by the PCM is of a low current design. The EVAP vacuum switch may be damaged if jumpered to voltage without this current limiting feature.
If a sticking solenoid is suspected, command the EVAP solenoid ON and OFF several times while watching the EVAP switch for the correct display.
EVAP System Charcoal Contamination Checking Procedure
- Remove EVAP Purge solenoid and the EVAP vacuum switch. Refer to R&R Procedures .
- Lightly tap both components on a hard surface.
- Check for the release of charcoal from either component.
- If charcoal contamination is present replace the EVAP Vapor canister, EVAP Purge solenoid, EVAP Vacuum switch and clean the EVAP purge hoses. Refer to the EVAP Purge Hose Cleaning Procedure .
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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If the EVAP purge solenoid or wiring is open or shorted DTC P1645 should be set.
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Checking if the switch/circuit is at fault.
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Ensuring correct vacuum line connection and checking if fault is present.
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Ensuring that the PCM isn't commanding the EVAP purge solenoid ON. If it isn't then the vacuum lines are on wrong or the EVAP solenoid is leaking.
-
Commanding the EVAP solenoid OFF to check if vacuum flows when it should not.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |||||
Turn the key ON. Is DTC P1645 also set? | -- | Go to DTC P1645 Evaporative Emission (EVAP) Vent Solenoid Contorl Circuit | ||||||
Does the display show Purging? | -- | |||||||
Does the display show Purging? | -- | Fault not present. Refer to Diagnostic Aids | ||||||
Ckeck the EVAP Purge Sol. display. Does the display show a duty cycle less than the value specified? | 9.8% | |||||||
Does the display show Purging? | 0% | Fault not present. Refer to Diagnostic Aids | ||||||
7 |
Was a repair performed? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |||||
8 | Replace the EVAP purge solenoid. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- | ||||
9 |
Does the display show No Flow? | -- | ||||||
10 | Using DMM J 39200 measure the voltage to ground at the EVAP vacuum switch connector terminal A (harness side). Is the voltage the same or more than the value specified? | 10.5 volts | ||||||
11 |
Is the resistance the same or less than the value specified? | 5 ohms | ||||||
12 | Replace the EVAP vacuum switch. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- | ||||
13 | Repair open in the ground circuit between the EVAP vacuum switch and ground. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- | ||||
14 | Repair open in EVAP Vacuum Switch Input circuit between the EVAP vacuum switch and PCM. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- | ||||
15 |
Is the terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |||||
16 | Replace the PCM. Refer to PCM Replacement/Programming . Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
