Powertrain, generic (extended)

P2B49 B Camshaft Position Actuator Position Sensor B Circuit Low Bank 1

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

With P2B49 the module reads too low a signal from position sensor B at the exhaust camshaft actuator of bank 1. A short between signal line and ground, a sensor with an internal short or a missing feed are the usual suspects. The nearest public manufacturer reference is P34BE on the Mercedes M176/M177: the sensor of exhaust solenoid 1 for CAMTRONIC, bank 1, described as shorted to ground. For P2B49 itself no manufacturer document is available. GM sets the comparable exhaust code of its L3B (P2C14) when the driver is on and the circuit shows at most 0.5 Ω to ground. Chafe points on the harness running along the cylinder head cover are worth checking first. Exhaust bank 1 high fault: P2B4A.

Likely causes

Signal line shorted to ground

Sensor shorted internally

Sensor feed missing

Symptoms

Check engine light on
Exhaust cam lift change switched off
Occasionally further sensor codes

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, static.nhtsa.gov, gsi.ext.gm.com.