DN21 - Rerun KOEO and KOER Self-Test W/EGR Vacuum Disconnected

- Disconnect vacuum hose from EGR valve and plug hose.

- Rerun Key On Engine Off (KOEO) and Key On Engine Running (KOER) Self-Test. Quick Test Appendix (Detailed Testing Instructions)

- Is Diagnostic Trouble Code (DTC) 334 present?

Yes -- Go to DN22. DN22 - Check EVP Sensor and EGR Valve Operation

No -- Check EGR Vacuum Regulator (EVR) solenoid for obstructions. Service as necessary. If OK, replace EVR solenoid. Reconnect all vacuum hoses. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)