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Diagnostic trouble code P0409 indicates: EGR Sensor A Circuit. It was set by your vehicle's onboard diagnostics system and will typically keep the check engine light on until it's addressed.
P0409 is part of the EGR OFF group. These ECUs support EGR OFF, which switches it off:
Upload your ECU file and DTC Doctor will detect this code (and any others) automatically, then remove it for good — no dealer visit, no guesswork.
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