Circuit Description
The Evaporative Emission (EVAP) System is used to prevent fuel vapors from venting to the atmosphere. The EVAP canister vent solenoid is normally open. This allows ambient air to flow through the EVAP canister to the fuel tank so that atmospheric pressure can be maintained in the fuel tank. The engine control module (ECM) controls the EVAP canister vent solenoid by providing ground to the EVAP canister vent solenoid control circuit. The ECM monitors the EVAP canister vent solenoid control circuit for low and high voltage faults. If the ECM detects that the voltage of the EVAP canister vent solenoid control circuit is above a predetermined threshold when the EVAP canister vent solenoid is commanded ON, DTC P0448 sets.
Conditions for Running the DTC
| • | DTC P0447 is not set. |
| • | The engine speed is more than 40 RPM. |
| • | The battery voltage is more than 8.05 volts and less than 18 volts. |
| • | The vehicle is moving. |
Conditions for Setting the DTC
| • | The voltage of the EVAP canister vent solenoid control circuit is above 1.25 volts when the EVAP canister vent solenoid is commanded ON. |
| • | The above condition is met for more than 0.5 seconds. |
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 |
Did the DTC fail this ignition? | Go to Step 3 | Go to Intermittent Conditions |
3 |
Did you find and correct the condition? | Go to Step 9 | Go to Step 4 |
4 |
Did DTC P0448 fail this ignition? | Go to Step 5 | Go to Step 7 |
5 | Test the control circuit of the EVAP canister vent solenoid for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the EVAP canister vent solenoid. Refer to Evaporative Emission Canister Vent Solenoid Replacement . Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | Go to Step 9 | -- |
9 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 10 |
10 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
