P01CBCylinder 1 Injection Timing Performance - Over Retarded
- 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
- Diesel engines must detect when fuel can no longer be injected at the correct crank angle – CARB requires this for every injector individually, hence one code per cylinder. The start of injection is not measured directly: during overrun with fuel cut-off the control module fires a tiny test injection into one cylinder (GM: about 1.5 mm³) and evaluates the resulting speed change at the crankshaft sensor. From this it learns how much extra energizing time the injector needs (Bosch calls this zero fuel calibration). This code means injector 1 needs clearly more energizing time than intended, i.e. it opens too late – GM sets it above 80 µs of extra time, after two trips. Documented users are GM's 6.6 litre Duramax (LML, L5P) and FCA's 3.0 litre EcoDiesel; Ford reports the same function under P2B11ff. Bulletins often point away from the injector: GM fixed false settings on 2020–2021 L5P trucks with new software and warns that vibration, for example from off-road tyres, disturbs the evaluation; FCA lists wrong injector correction codes, boost leaks and loose injector clamps.
- What you may notice
- Check engine light on (after two drive cycles)
- Louder combustion noise or knocking
- Rough idle
- Possibly smoke
- Likely causes
- LikelyInjector worn, coked or sticking (opens late, delivers too little)
- PossibleFalse setting from software or vehicle vibration (e.g. off-road tyres)
- PossibleWrong injector correction code stored after an injector replacement
- RareBoost leak or loose injector clamp
- RareContaminated fuel
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.