For 1990-2009 cars
Engine Controls Components
MAF, EVAP, EGR
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The EVAP vacuum switch is a normally closed switch positioned in the purge line between the canister and the EVAP purge valve. 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 vacuum switch signal to determine if the evaporative emission control system is working properly. If the EVAP vacuum 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 TP sensor, IAT sensor, MAP sensor, 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

• | The 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 Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.

• | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using the scan tool.

### 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 switch. A change in the display will indicate the location of the fault.

• | Incorrect vacuum hose routing. Verify that the vacuum hose routing to the canister purge vacuum switch and the canister purge solenoid is correct and that the vacuum hoses at the canister purge solenoid are not switched. Refer to Evaporative Emission Control System .

• | 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 P1441 to be set.

• | Faulty or damaged canister. A faulty canister may intermittenly allow charcoal into the EVAP purge solenoid, vacuum switch, and associated lines causing a DTC to be set.

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.

1. 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.

2. Determines if the PCM is able to control the EVAP purge solenoid valve.

3. Determines if the DTC will set under the conditions present when the DTC was originally stored. If not, the fault is intermittent.

4. 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.

#### DTC P1442 - EVAP Vacuum Switch Circuit

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the A Powertrain On Board Diagnostic (OBD) System Check
2 | With the ignition ON, engine not running, observe EVAP Vacuum Sw. display on the scan tool. Does EVAP Vacuum Sw. display No Purge? | -- | Go to Step 3 | Go to Step 4
3 |

1. Review and record scan tool Fail Records data.
2. Operate the vehicle within Fail Records conditions as noted.
3. Using a scan tool, monitor Status This Ign for DTC P1442.

Does the scan tool indicate DTC P1442 failed?

--

Go to Step 4

Refer to DTC P1442 Diagnostic Aids

4 |

1. Disconnect the EVAP vacuum switch electrical connector.
2. Connect a jumper between the EVAP vacuum switch harness connector terminals.
3. Observe EVAP Vacuum Sw. display on the scan tool.

Does EVAP Vacuum Sw. display No Purge?

--

Go to Step 6

Go to Step 5

5 |

1. Check for the following conditions:

• | For an open or short to ground in the EVAP vacuum switch signal circuit between the EVAP vacuum switch and the PCM.

• | For an open EVAP vacuum switch ignition feed circuit.

• | For a poor EVAP vacuum switch signal circuit connection at the PCM.

2. If a problem is found, repair it as necessary. Refer to Wiring Repair in Electrical Diagnosis.

Was a problem found?

--

Go to Step 11

Go to Step 7

6 |

1. Check for poor connection at EVAP vacuum switch.
2. If a problem is found, replace faulty terminal(s) as necessary. Refer to Wiring Repair in Electrical Diagnosis.

Was a problem found?

--

Go to Step 11

Go to Step 8

7 | Replace the PCM. Important:: The replacement PCM must be programmed. Go to PCM Replacement/Programming . Is action complete? | -- | Go to Step 11 | --
8 |

1. Check the EVAP purge hose for a restriction between the canister and the EVAP vacuum switch.

• | Refer to

(1) | To EVAP Canister (At Rear of Vehicle)
(2) | EVAP Vacuum Switch
(3) | PCV Valve
(4) | To Accessory
(5) | To Vacuum Brake Booster
(6) | Throttle Body
(7) | To Transaxle
(8) | Supercharger Bypass Solenoid (Boost Control Solenoid)
(9) | Supercharger Bypass Actuator (Bypass Valve Actuator)
(10) | Manifold Vacuum Source
(11) | Fuel Pressure Regulator
(12) | Supercharger Assembly
(13) | MAP Sensor
(14) | EVAP Canister Purge Valve

.

• | Refer to

(1) | To Vacuum Brake Booster
(2) | To Accessory
(3) | To EVAP Canister (At Rear of Vehicle)
(4) | Throttle Body
(5) | To Transaxle
(6) | EVAP Vacuum Switch
(7) | EVAP Canister Purge Valve
(8) | Fuel Pressure Regulator
(9) | PCV Valve
(10) | Intake Manifold

.

2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 9

9 |

1. Check the fuel tank vapor line for a restriction between the canister and the fuel tank.

• | Refer to

(1) | To EVAP Canister (At Rear of Vehicle)
(2) | EVAP Vacuum Switch
(3) | PCV Valve
(4) | To Accessory
(5) | To Vacuum Brake Booster
(6) | Throttle Body
(7) | To Transaxle
(8) | Supercharger Bypass Solenoid (Boost Control Solenoid)
(9) | Supercharger Bypass Actuator (Bypass Valve Actuator)
(10) | Manifold Vacuum Source
(11) | Fuel Pressure Regulator
(12) | Supercharger Assembly
(13) | MAP Sensor
(14) | EVAP Canister Purge Valve

.

• | Refer to

(1) | To Vacuum Brake Booster
(2) | To Accessory
(3) | To EVAP Canister (At Rear of Vehicle)
(4) | Throttle Body
(5) | To Transaxle
(6) | EVAP Vacuum Switch
(7) | EVAP Canister Purge Valve
(8) | Fuel Pressure Regulator
(9) | PCV Valve
(10) | Intake Manifold

.

2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 10

10 | Replace the EVAP vacuum switch. Go to EVAP Vacuum Switch . Is action complete? | -- | Go to Step 11 | --
11 |

1. Clear DTCs.
2. With the ignition ON, engine not running, observe EVAP Vacuum Sw. display on the scan tool.

Does EVAP Vacuum Sw. display No Purge?

--

System OK

Go to Step 2