Circuit Description
The exhaust gas recirculation (EGR) valve is vacuum operated. Vacuum for the EGR valve control system is supplied by a belt driven vacuum pump. The EGR valve vacuum control solenoid and the EGR valve vacuum vent solenoid work together to control the position of the EGR valve. The EGR valve vacuum control solenoid is supplied with 12 volts through the ignition 1 circuit. The EGR valve vacuum control solenoid is pulse width modulated through the EGR valve vacuum solenoid control circuit by the engine control module (ECM). The ECM monitors the voltage on the EGR valve vacuum solenoid control circuit. If the ECM detects a high voltage condition on this circuit, Diagnostic Trouble Code (DTC) P0490 sets.
Conditions for Running the DTC
| • | The Engine Run Time parameter is more than 0.5 seconds. |
| • | The Ignition 1 Signal parameter is between 11-18 volts. |
| • | The EGR Solenoid Command parameter has been commanded to more than 10 percent. |
Conditions for Setting the DTC
The ECM detects a high voltage condition on the EGR valve vacuum solenoid control circuit for more than 2 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 3 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. |
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 |
Does the EGR valve vacuum control solenoid click continuously when commanded with a scan tool? | Go to Step 3 | Go to Step 4 |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Intermittent Conditions |
4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 6 |
5 | Test for a short to voltage on the control circuit of the EGR valve vacuum control solenoid. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 7 |
6 | Test for an intermittent and for a poor connection at the EGR valve vacuum control solenoid. 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 10 | Go to Step 8 |
7 | Test for an intermittent and for a poor connection at the 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 10 | Go to Step 9 |
8 | Replace the EGR valve vacuum control solenoid. Refer to Exhaust Gas Recirculation Valve Solenoid Replacement . Did you complete the replacement? | Go to Step 10 | -- |
9 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | Go to Step 10 | -- |
10 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 11 |
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
