Powertrain, generic (extended)

P2B4A B Camshaft Position Actuator Position Sensor B Circuit High Bank 1

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P2B4A says the position sensor B signal of the bank 1 exhaust camshaft actuator is above its limit. An interrupted sensor ground, a short to a voltage source or a failed sensor are typical. No manufacturer describes P2B4A publicly, and the Mercedes CAMTRONIC bulletin does not include any high fault of this family. As a comparison only, GM checks the exhaust sliding-cam circuits of the 2.7-litre L3B for an unwanted link to supply voltage with the output switched off (P2C15, 0.5 Ω, 4 of 5 samples, Type A). The engine module keeps the exhaust lift system in its safe position until the fault is gone. CARB counts such sensors among the comprehensive components that need circuit monitoring. Exhaust low fault on bank 1: P2B49.

Likely causes

Sensor ground interrupted or connector corroded

Signal line shorted to a voltage source

Sensor failed

Symptoms

Check engine light on
Exhaust lift system kept in safe position
Usually unchanged driveability

Repair estimate

DifficultyMediumDIY possible

Parts and labour€60–600

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

b camshaft position actuator pos sensor b b1wiring harnessecm

References: law.cornell.edu, ntn-snr.com, gsi.ext.gm.com.