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 Running the DTC
| • | DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0441, P0443, P1120, P1121, P1220, P1221 not set. |
| • | ECT is less than 115°C (239°F). |
| • | IAT is greater than 3°C (37°F) at power up. |
| • | IAT is less than 80°C (176°F). |
| • | The difference between ECT and IAT is less than 10°C (50°F) at power up. |
| • | Engine speed is between 500 and 2500 RPM. |
| • | TP Angle is between 10% and 60%. |
| • | MAP is between 20 kPa and 80 kPa. |
| • | BARO is greater than 75 kPa. |
| • | Purge not enabled. |
Conditions for Setting the DTC
| • | The PCM detects high signal voltage on the EVAP vacuum switch signal circuit when the PCM is not commanding purge ON. |
| • | The fault is present for 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important: Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM\TAC modules.
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 an intermittent condition, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the 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 Emission Hose Routing Diagram .
Does the scan tool indicate, EVAP vacuum switch No Purge? | -- | ||
3 |
Does the EVAP vacuum switch status change to Purge when the engine is started? | -- | ||
4 |
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 | |
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 | |||
6 |
Is the test lamp illuminated? | -- | ||
7 | Connect a fused jumper wire between the EVAP vacuum switch harness connector terminals. Does the scan tool indicate EVAP vacuum switch No Purge? | -- | ||
8 | Measure the voltage at the signal circuit of the EVAP vacuum switch harness connector using a DMM J 39200 connected to a ground. Does a DMM indicate a voltage near the specified value? | B+ | ||
9 |
Does the DMM indicate an infinite resistance? | -- | ||
10 | Check the continuity of the EVAP vacuum switch signal circuit from the vacuum switch harness connector to the PCM connector using a DMM J 39200 . Does the DMM indicate a resistance less than the specified value? | 5ohms | ||
11 | Replace the EVAP canister. Refer to Evaporative Emission System Cleaning . The EVAP system must be inspected and/or cleaned before replacing any component. Is the action complete? | -- | -- | |
12 | Repair the restricted or kinked hose between the canister and EVAP vacuum switch. Refer to Evaporative Emission System Cleaning for the cleaning procedure. Is the action complete? | -- | -- | |
13 | Repair the open ground circuit. Is the action complete? | -- | -- | |
14 | Check the connections at the EVAP vacuum switch. Did you find and correct the condition? | -- | ||
15 |
Important: Contamination can cause the switch to fail. Refer to Evaporative Emission System Cleaning for the inspection/cleaning procedures. Replace the EVAP vacuum switch. Refer to Evaporative Emission Purge Vacuum Switch Replacement . Is the action complete? | -- | -- | |
16 | Repair the shorted signal circuit to ground. Is the action complete? | -- | -- | |
17 | Repair the open signal circuit. Is the action complete? | -- | -- | |
18 | Check the connections at the PCM. Did you find and correct the condition? | -- | ||
19 |
Important: Contamination can cause the solenoid to fail open. Refer to Evaporative Emission System Cleaning for the inspection/cleaning procedures. Replace the EVAP canister purge solenoid valve, refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the action complete? | -- | -- | |
20 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement . Replace the PCM. Is the action complete? | -- | -- | |
21 |
Does the scan tool indicate that this test ran and passed? | -- | ||
22 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
