P04D9
Closed Loop EGR Control At Limit Flow Too Low
With EGR running in closed loop the controller has driven the actuator to its maximum opening but cannot reach the required EGR flow. The valve, cooler, or pipework is restricted enough that even full open does not deliver the modelled rate.
With EGR running in closed loop the controller has driven the actuator to its maximum opening but cannot reach the required EGR flow. The valve, cooler, or pipework is restricted enough that even full open does not deliver the modelled rate.
Common causes
- high
EGR cooler clogged with soot
One of the most commonly reported causes for this code — check this first.
Typical part cost: $330-1650
- medium
Valve effective opening reduced by carbon
A plausible cause — test and verify before replacing parts.
Typical part cost: $330-1650
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Related codes
See related trouble codes
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Frequently asked questions
What does P04D9 mean?
P04D9 means "Closed Loop EGR Control At Limit Flow Too Low". It is a generic OBD-II code that points to a fault in the auxiliary emission controls.
What are the most common causes of P04D9?
egr cooler clogged with soot; valve effective opening reduced by carbon — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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