Exhaust Gas Recirculation: Testing and Inspection

(_P0401_)
- The scan tool indicates Diagnostic Trouble Code (DTC) PO42O: Insufficient flow in the Exhaust Gas Recirculation PO4O1 (EGR) system.

Description
Deterioration (clogging, leakage, etc.) in the EGR line or EGR valve is detected by means of the changes in manifold absolute pressure before and after the operation of the EGR valve.
If deterioration has been detected during two consecutive driving cycles, the MIL will come on and DTC PO4O1 will be stored.

Possible Causes
- Clogging, leakage in the EGR line
- Faulty EGR valve








(_P1491_)
- The scan tool indicates Diagnostic Trouble Code (DTC) P1491: A malfunction in the Exhaust Gas Recirculation P1491 (EGR) system.