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DTC code page

P0391: Camshaft Position Sensor B Circuit Range/Performance (Bank 2)

Quick answer: The Bank 2 camshaft position sensor B signal exists, but its pattern or timing is not believable enough to trust.

Drivers also search this fault as bank 2 cam sensor B range performance, P0391 bank 2 exhaust cam performance, erratic bank 2 cam sensor B signal.

Severity: high Family: powertrain Related paths: 15
Meaning

What P0391 usually means

P0391 means the ECU can see the Bank 2 sensor B signal, but that signal fails plausibility checks. That usually points to an erratic exhaust-cam waveform on Bank 2, a target-wheel problem, phaser or timing drift, or wiring noise that distorts the signal rather than killing it completely.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • See whether P0019 or startup-rattle clues are present because they raise the Bank 2 mechanical branch fast.
  • Inspect the Bank 2 sensor B connector before assuming the timing set is automatically bad.
  • Capture freeze-frame so you know whether the implausible signal appears on startup, hot idle, or under load.
Driving risk

Can you keep driving?

P0391 can turn into reduced power or repeat no-start behavior if the ECU keeps losing confidence in Bank 2 exhaust-cam timing.

High urgency: If symptoms are active, reduce driving and diagnose quickly before secondary damage builds.
Likely causes

Common causes behind this code

  • Bank 2 camshaft position sensor B producing an erratic waveform
  • Target wheel or trigger issue on the Bank 2 exhaust camshaft
  • Timing-chain stretch or phaser-control trouble on Bank 2
  • Connector or wiring fault adding noise to the Bank 2 sensor B signal
  • Oil-condition or VVT-control trouble making Bank 2 exhaust-cam timing unstable

Cause phrases often tied to this code: bank 2 exhaust cam waveform, timing chain stretch, bank 2 phaser issue, wiring noise, target wheel problem.

Diagnostic order

Suggested workflow

  1. Note when the fault sets and whether startup noise or reduced power travel with it.
  2. Inspect Bank 2 cam sensor B wiring and connector condition.
  3. Compare live data for Bank 2 exhaust-cam activity with any correlation or VVT faults present.
  4. Verify oil condition and phaser-control context if timing-control codes are also stored.
  5. Inspect sensor output and Bank 2 mechanical timing if the signal remains implausible.
Avoid guesswork

Common mistakes

  • Replacing the sensor before checking for Bank 2 timing drift or phaser problems.
  • Ignoring oil condition when performance codes travel with VVT faults.
  • Treating P0391 like a dead-sensor code when it is usually a plausibility issue.
Repair path

Practical fix guidance

  • Repair the proven Bank 2 signal-quality or timing cause instead of guessing between sensor, solenoid, and chain.
  • After repair, confirm stable idle, reliable starts, and clean Bank 2 exhaust-cam data.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P0391

Useful when the driver knows the wording but not the exact DTC yet.

  • bank 2 cam sensor B range performance
  • P0391 bank 2 exhaust cam performance
  • erratic bank 2 cam sensor B signal
Related search intent

Queries this page can answer naturally

  • P0391 code meaning
  • what does P0391 mean
  • bank 2 cam sensor B out of range
  • bank 2 exhaust cam performance code
FAQ

Quick questions about P0391

How is P0391 different from P0390?

P0390 is the broad Bank 2 sensor B circuit fault, while P0391 means the signal exists but its quality or timing is not believable.

Can timing-chain stretch cause P0391?

Yes. Mechanical timing drift on Bank 2 is one of the most important real-world causes.

Why does startup rattle matter with P0391?

Because noise at startup makes the one-bank mechanical timing branch much more credible than a random isolated sensor theory.