OBD-II · Engine and powertrain (P)
P0409
EGR sensor A circuit
What it means
The EGR valve position sensor (usually built into the EGR valve) circuit has an electrical fault.
Symptoms
- engine warning light
- EGR may be switched off, sometimes with reduced power
- often no noticeable change
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | failed EGR valve position sensor |
| 02 | wiring open or short |
| 03 | corroded connector |
| 04 | 5 V reference fault |
What to check, step by step
- 01Inspect the EGR valve connector and wiring for corrosion, oil and chafing.
- 02With key on, check the 5 V reference, ground and signal.
- 03Compare live position against the commanded position.
- 04If wiring is good, replace the EGR valve (the sensor is usually not sold separately).