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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
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.
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 |
Does the test light illuminate? | -- | ||
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 | 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+ | ||
9 |
Does the DVM indicate infinite resistance? | -- | ||
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 | ||
11 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . The EVAP system must be inspected and/or cleaned before replacing any component. Is the action complete? | -- | -- | |
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? | -- | -- | |
13 | Repair the open ground circuit. Is the action complete? | -- | -- | |
14 | Check connections at the EVAP vacuum switch. Was a problem found and corrected? | -- | ||
15 |
Important: Contamination can cause the switch to fail. Refer to Evaporative Emission System Cleaning for 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. Was a problem found and corrected? | -- | ||
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? | -- | -- | |
20 |
Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
21 |
Does the scan tool indicate that this test ran and passed? | -- | ||
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 |
