| Table 1: | DTC P0498 Evaporative Emission (EVAP) Vent Solenoid Control Circuit Low Voltage |
Circuit Description
The evaporative emission (EVAP) canister vent valve is used for EVAP system diagnostics. The EVAP canister vent valve is a normally open valve. Battery positive voltage is supplied directly to the EVAP canister vent valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is less than a predetermined value when the circuit is commanded OFF, this DTC sets.
The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister vent valve.
Control Module Command | EVAP Canister Vent Valve Position |
|---|---|
ON | CLOSED |
OFF | OPEN |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0498 Evaporative Emission (EVAP) Vent Solenoid Control Circuit Low Voltage
Conditions for Running the DTC
| • | Before the ECM can report DTC P0498 failed, DTC P0451 must run and pass. |
| • | The engine speed is more than 80 RPM. |
| • | The ignition 1 voltage is between 10.5-18 volts. |
| • | The ECM has commanded the EVAP canister vent valve ON and OFF at least once during the ignition cycle. |
| • | DTC P0498 runs continuously once the above conditions have been met. |
Conditions for Setting the DTC
| • | The ECM detects the voltage on the EVAP canister vent valve control circuit is less than 2.6 volts when the driver is commanded OFF. |
| • | The condition exists for more than 4 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | 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 emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views . |
| • | If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if a condition exists. An audible click should be heard when the EVAP canister vent valve is commanded ON and OFF. Repeat the commands as necessary.
-
This step tests the battery positive voltage circuit to the EVAP canister vent valve.
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 - Vehicle? | Go to Step 2 | |
Did the DTC fail this ignition? | Go to Step 4 | Go to Step 3 | |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Diagnostic Aids |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 7 | |
5 | Test the control circuit between the EVAP canister vent valve and the engine control module (ECM) for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
6 | Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 |
Did you complete the repair? | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. 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 | |
