P1491 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P1491 – Exhaust Gas Recirculation Valve Insufficient Lift

 

P1491 Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

P1491 Possible Causes

 

Faulty Exhaust Gas Recirculation Valve,Exhaust Gas Recirculation Valve harness is open or shorted,Exhaust Gas Recirculation Valve circuit poor electrical connection,Exhaust Gas Recirculation Valve clogged,Exhaust gas leaks

 

P1491 Description

 

The exhaust gas recirculation (EGR) system reduces oxides of nitrogen (NOx). NOx is generated by high combustion temperatures. The EGR system lowers peak combustion temperature by recirculating inactive exhaust gas into the air/fuel mixture, thus reducing NOx emissions. The EGR valve position sensor is built into the EGR valve and detects the amount of valve lift. The command value for the target valve lift is previously stored in the powertrain control module (PCM) so that exhaust gas recirculation can be optimized according to driving conditions. Comparing this command value with the EGR valve position sensor output signal value, the PCM controls the EGR valve to make the amount of actual valve lift equal to the command value. If the EGR valve position sensor output signal value differs greatly from the command value in the PCM memory for a set period of time, the EGR valve or the EGR valve position sensor is considered faulty and a DTC is stored.