P2B40A Camshaft Position Actuator Position Sensor B Range/Performance Bank 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- With P2B40 the wiring of the intake-side sensor B (camshaft A, bank 1) is electrically fine, but its signal does not fit what the engine module commanded. Engines with switchable cam lift use such feedback to confirm that a pin really moved; GM's L3B, as a comparable case under P2C06, logs a fault when the Hall feedback shows movement although no shift was requested, or when the extending, extended and retracted states do not appear. Mercedes documents the same fault type for bank 2 as P2B44 (CAMTRONIC, M176/M177) and cures it with new software and revised actuators. For P2B40 itself there is no public manufacturer text. A sticking or worn actuator is more likely here than a wiring fault.
- What you may notice
- Check engine light on
- Valve-lift change held in a safe position
- Uneven running when the system tries to switch
- Likely causes
- LikelyActuator pin sluggish or sticking (wear, oil sludge)
- PossibleEngine control software outdated (Mercedes CAMTRONIC update)
- PossibleSensor signal disturbed by loose contact
- RareCam sleeve or shift groove damaged
- 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.