OBD-II code · Powertrain (generic)
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.
Is it safe to drive with P04D9?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyEGR cooler clogged with soot
- PossibleValve effective opening reduced by carbon
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1.5–5 h
- Emissions test
- Likely to fail
- Parts involved
- Egr Valve A, Egr Cooler A, Egr Pipework
Related codes
- P04D6Exhaust Brake Input Circuit High
- P04D7Exhaust Brake Input Circuit Intermittent or Erratic
- P04D8Excessive Time To Enter Closed Loop EGR Control
- P04DAClosed Loop EGR Control At Limit Flow Too High
- P04DBCrankcase Ventilation System Disconnected
- P04DCFuel Fill Door Position Sensor Circuit Range or Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.