P016BClosed Loop Air/Fuel Ratio Control At Limit - System Too Rich
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- With closed-loop control the engine module corrects the injected fuel using the oxygen sensor: short-term fuel trim reacts within fractions of a second, long-term trim stores a learned base correction per load and speed range. Positive values mean fuel is being added because the mixture was lean, negative values mean fuel is being removed; around ±10 % is normal. P016B means the mixture control as a whole has reached its lower limit: it already removes as much fuel as allowed and the mixture is still rich. In substance it matches P0172, but without a bank reference – for manufacturers whose strategy evaluates the control loop as a whole. CARB requires a fault once the adaptation has used up its range. No manufacturer document using exactly this code was found; Hyundai documents the lean counterpart P016C. Typical causes are those of a rich mixture: excessive fuel pressure, leaking injectors or an open purge valve.
- What you may notice
- Check engine light on (after two drive cycles)
- Poor cold start, rough idle
- Higher consumption, fuel smell
- Often together with P0172
- Likely causes
- PossibleFuel pressure too high / high-pressure pump or regulator fault (direct injection)
- PossibleLeaking injectors
- PossiblePurge valve open
- RareOxygen sensor or air flow/pressure sensor offset, control module software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.