Circuit Description
The evaporative emission (EVAP) system includes the following components:
| • | Fuel tank |
| • | EVAP vent solenoid |
| • | Fuel tank pressure sensor |
| • | Fuel pipes and hoses |
| • | Fuel vapor lines |
| • | Fuel cap |
| • | EVAP canister |
| • | Purge lines |
| • | EVAP canister purge valve |
| • | EVAP service port |
The EVAP system is inspected by applying vacuum to the EVAP system and monitoring for a vacuum decay. The engine control module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal.
At the appropriate time, the EVAP canister purge valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire EVAP system. After the desired vacuum level has been achieved, the EVAP canister purge valve is turned OFF, sealing the system.
Conditions for Setting the DTC
| • | The ignition is ON. |
| • | The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF at the end of 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
Diagnostic Aids
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The fail counter and the pass counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature, etc., that were noted. This will isolate when the DTC failed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Perform the Diagnostic System Check-Engine Controls. Is the check complete? | -- | Go to Step 2 | |
2 |
Does the solenoid turn ON and OFF with each command? | -- | Go to Step 3 | Go to Step 5 |
3 |
Does the current draw measure less than the specified value? | 0.75 A | Go to Diagnostic Aids | Go to Step 4 |
4 |
Does the DVM display infinite resistance? | -- | Go to Step 12 | Go to Step 10 |
5 |
Does the test light turn ON and OFF with each command? | -- | Go to Step 8 | Go to Step 6 |
6 | With the test light connected to ground, probe the ignition feed circuit, at terminal 1 in the solenoid harness connector. Does the test light illuminate? | -- | Go to Step 7 | Go to Step 11 |
7 |
Does the solenoid operate? | -- | Go to Step 9 | Go to Step 10 |
8 | Inspect the connections at the solenoid. Is a condition found and corrected? | -- | Go to Step 14 | Go to Step 12 |
9 | Inspect the connections at the ECM. Is a condition found and corrected? | -- | Go to Step 14 | Go to Step 13 |
10 | Repair the faulty solenoid control circuit. Is the repair complete? | -- | Go to Step 14 | -- |
11 | Repair the faulty solenoid ignition feed circuit. Is the repair complete? | -- | Go to Step 14 | -- |
12 | Replace the solenoid. Is the replacement complete? | -- | Go to Step 14 | -- |
13 |
Is the replacement complete? | -- | Go to Step 14 | -- |
14 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | Go to Step 15 | Go to Step 2 |
15 | Are any DTCs displayed that have not been diagnosed? | -- | System OK |
