Exhaust Gas Recirculation: Testing and Inspection

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

Description
Deterioration (clogging, leakage, etc.) in the EGR line or EGR valve is detected by means of the changes in mass air flow 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
- Air Cleaner (ACL) element damaged or dirty












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




(_P1498_)
- The scan tool indicates Diagnostic Trouble Code (DTC) P1498: A high voltage problem in the Exhaust Gas Recirculation (EGR) valve lift sensor circuit.