P0390

Code

Generic P — Powertrain

Camshaft Position Sensor B Circuit Bank 2

Brand: Generic

Type: P — Powertrain

Views: UK: 28 EN: 35 RU: 39

AI status

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Page language: EN

Causes

Faulty camshaft position sensor B (bank 2)
Open, short to ground, or short to voltage in sensor wiring or harness
Poor connector contact or corrosion at the sensor or ECM connector
Oil or debris contamination of the sensor
Damaged reluctor/target wheel or timing component (cam, timing chain/belt, phaser)
Faulty ECM or internal driver fault

Symptoms

Check Engine Light (MIL) illuminated with stored P0390
Hard start, extended crank time, or no-start condition (intermittent or permanent)
Rough idle, misfires, or reduced engine power
Poor fuel economy or increased emissions
Intermittent stalling or limp-home mode on some vehicles

What to check

Use a scan tool to read freeze frame, pending codes and live cam/crank data for bank 2 sensor B
Visually inspect sensor, connector and wiring on bank 2 for damage, corrosion, oil, or disconnected pins
Perform wiggle test on wiring and connector while monitoring live data to reproduce the fault
Verify battery voltage and chassis/engine/ECM grounds are clean and tight
Check for related cam/crank correlation codes (cam vs crank angle mismatch)
Inspect timing components (timing chain/belt, cam phaser, reluctor/target) if mechanical timing issues are suspected

Signal parameters

Sensor type may be Hall-effect (digital) or variable reluctor (VR) depending on engine — confirm OEM type before testing
Hall-effect: reference supply typically 5 V (or 12 V on some systems), signal pulses ~0–5 V (square wave) synchronized to cam rotation
VR (magnetic) sensor: AC sine-like waveform, low amplitude at idle (hundreds of mV to ~1–2 VAC) increasing with engine speed
Expected behavior: consistent pulse frequency and amplitude proportional to RPM, correct phase relationship to crankshaft signal (cam-to-crank correlation)

Diagnostic algorithm

Safety: disable ignition and allow engine to cool if required. Use eye protection when working near rotating components.
Read and record DTCs, freeze-frame data and live cam/crank signals with a scan tool. Note when fault sets (cold/hot, idle/load).
Visually inspect sensor B (bank 2), connector and wiring for damage, oil, corrosion, or loose pins. Repair or clean as required.
Clear codes and perform a road or crank/run test while monitoring live camshaft sensor B signal. See if code returns and under what conditions.
Backprobe the sensor connector: verify reference voltage (usually 5 V), ground continuity, and signal presence while cranking/running. Replace wiring or repair shorts/opens as indicated.
If available, use an oscilloscope to verify waveform shape and amplitude (square wave for Hall, sine for VR) and check cam-to-crank correlation. Compare to known-good pattern or OEM specifications.
Check continuity/resistance of sensor circuit to the ECM and inspect ECM connector pins for corrosion or damage.
If wiring and connector checks pass but signal is absent or abnormal, replace the camshaft position sensor B and retest.
If problem persists after sensor replacement, inspect timing components (cam phaser, chain/belt, reluctor wheel) for damage or skewing of cam timing. Repair mechanical faults and retest.
If all hardware and wiring are good, consider ECM fault; confirm with OEM diagnostics before replacing ECM.

Likely causes

Failed camshaft position sensor B on bank 2
Damaged or disconnected wiring/connector between sensor and ECM
Corroded/contaminated connector causing intermittent signal
Reluctor/target wheel damage or incorrect cam timing

Fault status

⚠️ Status

MIL (Check Engine) illuminated. DTC P0390 stored in ECM memory; may be pending or freeze-frame recorded. Some vehicles may enter reduced-performance or no-start mode depending on ECU strategy.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3.0 hours