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.
Affected components
- Egr valve a
- Egr valve b
- Ecm
Common causes
- High likelihood: One EGR valve sluggish at cold
- Medium likelihood: Carbon-clogged passages on one channel
Possible symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
- Reduced-power or limp mode may occur
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.