Detection Condition

DTC P0402 indicates Self-Test has indicated Differential Pressure Feedback EGR (DPFEGR) signal at idle is more than at KOEO by a calibrated amount.

• 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.
• DPFEGR Sensor Description
  
  Measures actual pressure drop across the metering orifice and relays a proportional voltage signal (0-5 volts) to PCM.