OBD-II code · Powertrain (generic)
P04D8 Excessive Time To Enter Closed Loop EGR Control
After cold start the ECU operates EGR open-loop until preconditions (cooler temperature, sensor warm-up, engine load) are met, then transitions into closed-loop control. The transition is taking too long - typically due to a slow EGR temperature sensor, a stuck EGR valve still warming up, or a long-trip drive cycle that does not meet load conditions.
Is it safe to drive with P04D8?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyEGR temperature sensor responds slowly
- PossibleShort-trip operation - load conditions not met
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
- 1–3 h
- Emissions test
- Likely to fail
- Parts involved
- Egr Valve A, Egr Temperature Sensor A
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.