P2D1C
Cold Start EGR A/B Ratio Performance
During cold start, the ratio between EGR channel A and B flow does not match the calibrated cold-start strategy. One channel responds slower or sticks at low temperature.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Common causes
Ordered by how often each turns out to be the cause.
- One EGR valve sluggish at coldCommon
- Carbon-clogged passages on one channelPossible
Parts involved
- EGR Valve A
- EGR Valve B
- ECM
P2D1C is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.