Detection Condition
- DTC P0401 indicates self-test has detected insufficient EGR flow.
- DTC P1408 indicates EGR flow is less than required calibrated limit.
- EGR System Description - EGR system receives signals from Engine Coolant Temperature (ECT), Mass Airflow/Intake Air Temperature (MAF/IAT), Throttle Position (TP), and Crankshaft Position (CKP) sensors to provide PCM with information on engine operating conditions. Before EGR system is activated, engine must be warm, stable and running at a moderate load and RPM. PCM deactivates EGR during idle, extended wide open throttle or when a failure is detected in an EGR component or EGR required component.
- EGR Vacuum Regulator (EGRVR) Solenoid Description - EGRVR solenoid receives a variable duty cycle signal from PCM. The higher the duty cycle, the more vacuum the solenoid diverts to the EGR valve.
- EGR Valve Description - An increase in vacuum acting on the EGR valve diaphragm overcomes the valve spring and begins to lift EGR valve pintle off its seat, allowing exhaust gas to enter intake manifold.
- EGR Orifice Tube Description - One side of the EGR orifice tube is exposed to exhaust gas backpressure and the other side is exposed to the intake manifold, causing a pressure drop across the orifice whenever there is EGR flow. When EGR valve closes, there is no longer any flow across the metering orifice and pressure on both sides of the orifice is the same.
- Differential Pressure Feedback EGR (DPFEGR) Sensor Description - Measures actual pressure drop across the metering orifice and relays a proportional voltage signal (0-5 volts) to PCM.