P0409
Exhaust Gas Recirculation Sensor "A" Circuit
DTC P0409, sometimes indicated as P040900 is an OBD diagnostic trouble code indicating a generic fault with the vehicle powertrain (i.e. engine and gearbox). This code identifies an error with the auxiliary emissions system causing exhaust gas recirculation sensor "a" circuit.
The exhaust gas recirculation (EGR) sensor measures the amount of EGR flow. The P0409 code means that the EGR sensor signal is not within the manufacturer's specifications.
The most common cause of this code is a dirty or contaminated EGR sensor. The sensor can be cleaned with a solvent, but be sure to read the manufacturer's instructions carefully.
Another possible cause is a defective EGR valve. If the valve is stuck open, it will allow too much EGR flow and cause the sensor to register a higher reading than normal.
If the code is caused by a dirty or contaminated sensor, cleaning the sensor should solve the problem. If the code is caused by a defective valve, the valve will need to be replaced.
- P0409: Exhaust Gas Recirculation Sensor A Circuit
- P0409: Exhaust Gas Recirculation Sensor "A" Circuit
- P0409: EGR Flow Sensor A Circuit
- P0409: Exhaust gas recirculation (EGR) sensor A – circuit malfunction
- P0409 00: Exhaust gas recirculation (EGR) sensor A - circuit malfunction
Bulletins are notices put out by manufacturers in conjunction with the NHTSA to notify the public of manufacturing issues or changes.
- SB-10-N-001 - ELECTRICAL SYSTEM
ISUZU: Isuzu: repeating egr dtc's P042E, P0403, P0404, P0409, egr valve connector terminal spread. Technician diagnosis for dtc codes usually results in replacement of the egr valve. Investigation of returned egr valves shows that there is no f