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

### Circuit Description

The EVAP vacuum switch is a normally closed switch connected to ground, mounted in the vacuum line between the EVAP canister and the EVAP solenoid. 12 volts is supplied to the switch through a pull-up resistor in the PCM. When the PCM commands the EVAP canister purge solenoid valve open (purge ON) and engine vacuum draws the evaporative emissions from the canister, the EVAP vacuum switch opens (signal voltage high) providing feedback to the PCM that the EVAP system is operating. When the PCM commands purge OFF, the EVAP vacuum switch closes (signal voltage low) confirming purging has ceased.

### Conditions for Setting the DTC

• | DTCs P0100, P0101, P0102, P0103, P0106, P0323, P0325, P0327, P0332, P0335, P0336, P0372, P0400, P0403, P0410, P0412, P0420, P0430,P0441, P0443, P0500, P0502, P0503, P0506, P0507, P0530, P0531, P0719, P0758, P1415, P1642, P1652 not set.

• | ECT less than 115°C (239°F)

• | IAT greater than 3°C (37°F)

• | Engine speed between 500 and 3000 RPM

• | TP Angle less than 50%

• | MAP less than 70 kPa

• | BARO greater than 77 kPa

• | Purge not enabled

• | The PCM detects high signal voltage on the EVAP vacuum switch signal circuit when the PCM is not commanding purge ON.

• | Fault present for 5 seconds

### Action Taken When the DTC Sets

• | The PCM will illuminate the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.

• | The PCM will record operating conditions at the time the diagnostic fails. The first time the diagnostic fails, this information will be stored in Failure Records. If the diagnostic reports a failure on the second consecutive drive trip, the operating conditions at the time of failure will be written to Freeze Frame and the Failure record will be updated.

### 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 (Current DTC) will clear when the diagnostic runs and does not fail.

• | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | PCM battery voltage is interrupted.

• | Using a Scan tool.

### Diagnostic Aids

Before replacing any components, visually/physically check for the following:

• | Mis-routed harness.

• | Rubbed through wire insulation.

• | Broken wire inside the insulation.

• | Kinked or damaged vacuum hoses.

• | Physically damaged system components.

• | Inspect components and vacuum lines for traces of carbon or other contaminants. The presence of foreign material may be causing a restriction in the system or preventing the solenoid valve from closing properly. Either condition may cause a DTC to set.

For intermittents, refer to Symptoms .

### Test Description

Number(s) below refer to step numbers on the diagnostic table.

1. Since the vacuum switch only requires a vacuum of only a few inches of water to operate (a very small unit of vacuum), a properly operating switch will transition even with the canister end of the hose disconnected and un-plugged.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Important: This DTC will set if the vacuum lines at the EVAP purge solenoid are reversed, Refer to under hood emission label for proper routing.

1. Turn the ignition ON, engine OFF.
2. Using the scan tool, check the EVAP vacuum switch status.

Does the scan tool indicate, EVAP vacuum switch No Purge.

--

Go to Step 3

Go to Step 6

3 |

1. Start the engine.
2. Using the scan tool, check the EVAP vacuum switch status.

Does the EVAP vacuum switch status change to Purge when the engine is started?

--

Go to Step 19

Go to Step 4

4 |

1. Start the engine. Increase the Idle speed to 1500 RPM.
2. Using the scan tool, command the EVAP canister purge solenoid valve ON and OFF while observing the EVAP vacuum switch status.

Important: When the EVAP solenoid is commanded ON then OFF, the scan tool display should change from Purge to No Purge almost immediately.

Does the scan tool indicate No Purge within the time period indicated?

5 seconds

Go to Diagnostic Aids

Go to Step 5

5 |

1. Turn the engine OFF.
2. Disconnect the purge hose from the canister (the vacuum line from the EVAP vacuum switch). Refer to Evaporative Emission Canister Replacement .
3. Start the engine. Increase the Idle speed to 1500 RPM.
4. Using the scan tool, command the EVAP canister purge solenoid valve ON and OFF while observing the EVAP vacuum switch status.

Important: When the EVAP solenoid is commanded ON then OFF, the scan tool display should change from Purge to No Purge almost immediately.

Does the scan tool indicate No Purge within the time period indicated?

5 seconds

Go to Step 11

Go to Step 12

6 |

1. Disconnect the EVAP vacuum switch harness connector.
2. With a test light (J 34142-B) connected to B+, probe the ground circuit at the EVAP vacuum switch harness connector.

Does the test light illuminate?

--

Go to Step 7

Go to Step 13

7 | Connect a fused jumper wire between the EVAP vacuum switch harness connector terminals. Does the scan tool indicate EVAP vacuum switch No Purge? | -- | Go to Step 14 | Go to Step 8
8 | Using a DVM (J 39200) connected to ground, measure voltage at the signal circuit of the EVAP vacuum switch harness connector. Does the DVM indicate voltage near the specified value? | B+ | Go to Step 18 | Go to Step 9
9 |

1. Turn the ignition OFF.
2. Disconnect the PCM connector C2.
3. Using a DVM J 39200, check for continuity between the EVAP vacuum switch signal circuit and ground.

Does the DVM indicate infinite resistance?

--

Go to Step 10

Go to Step 16

10 | Using DVM J 39200, check continuity of the EVAP vacuum switch signal circuit from the vacuum switch harness connector to the PCM connector. Does the DVM indicate resistance is less than the specified value? | 5 ohms | Go to Step 20 | Go to Step 17
11 | Replace the EVAP canister, refer to Evaporative Emission Canister Replacement . The EVAP system must be inspected and/or cleaned before replacing any component. Refer to Evaporative Emission System Cleaning . Is the action complete? | -- | Go to Step 21 | --
12 | Repair restricted or kinked hose between canister and EVAP vacuum switch, refer to Evaporative Emission System Cleaning for cleaning procedure. Is the action complete? | -- | Go to Step 21 | --
13 | Repair the open ground circuit. Is the action complete? | -- | Go to Step 21 | --
14 | Check connections at the EVAP vacuum switch. Was a problem found and corrected? | -- | Go to Step 21 | Go to Step 15
15 | Important: Contamination can cause the switch to fail. Refer to Evaporative Emission System Cleaning for inspection/cleaning procedures. Replace EVAP vacuum switch, refer to Evaporative Emission Purge Vacuum Switch Replacement . Is the action complete? | -- | Go to Step 21 | --
16 | Repair the shorted signal circuit to ground. Is the action complete? | -- | Go to Step 21 | --
17 | Repair the open signal circuit. Is the action complete? | -- | Go to Step 21 | --
18 | Check the connections at the PCM. Was a problem found and corrected? | -- | Go to Step 21 | Go to Step 20
19 | Important: Contamination can cause the solenoid to fail open. Refer to Evaporative Emission System Cleaning for inspection/cleaning procedures. Replace the EVAP canister purge solenoid valve, refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Is the action complete?

--

Go to Step 21

--

20 | Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Step 21 | --
21 |

1. Using the scan tool, select DTC, Clear Info.
2. Start the engine and idle at normal operating temperature.
3. Select DTC, Specific, then enter the DTC number which was set.
4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 22

Go to Step 2

22 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK