Engine

P0394 — Camshaft Position Sensor "B" Circuit Intermittent (Bank 2)

Severity: medium Drive with care, to a shop

What P0394 means

The camshaft position sensor B on bank 2 tells the engine computer where the camshaft is, so it can time fuel injection and spark. P0394 sets when that signal drops out or becomes erratic without failing completely. The cause is most often electrical, such as a bad connection or a wiring break.

Symptoms

  • Check Engine Light on
  • Intermittent rough idle or bucking
  • Hesitation or power loss when accelerating
  • Occasional stalling
  • Misfire-like feel
  • Long cranking or hard starting

Possible causes

  1. Intermittent open or short in the sensor B wiring or connector
  2. Failing camshaft position sensor B
  3. Corroded terminals or poor power or ground to the sensor
  4. Damaged or contaminated tone ring (reluctor) on the camshaft
  5. Chafed harness near hot or vibrating parts
  6. PCM input circuit fault (rare)

How to diagnose

  1. Read codes and freeze frame data, and note any related camshaft or crankshaft sensor codes
  2. Inspect the bank 2 sensor connector and harness for oil, corrosion, cracks and chafing
  3. Wiggle the harness and connector with the engine running while watching the signal and idle quality
  4. Check power, ground and reference voltage at the sensor connector with a multimeter
  5. Inspect the sensor and its mounting for looseness or debris
  6. Scope the sensor signal and compare it to the crankshaft signal
  7. Test the wiring to the PCM for opens and shorts
  8. Check the camshaft tone ring and valve timing alignment

Common fixes

  • Repair the wiring or replace the damaged connector or terminals
  • Replace camshaft position sensor B
  • Clean terminals and restore good power and ground to the sensor
  • Replace a damaged tone ring or correct the valve timing
  • Repair or replace the PCM only after confirming it is faulty

Questions and answers

What does P0394 mean?

It means the signal from camshaft position sensor B on bank 2 is dropping out intermittently. The PCM briefly loses information about camshaft position.

Can I drive with P0394?

Short trips to a shop are possible, but the engine can stall or lose power suddenly. Do not put off diagnosis.

Should I replace the sensor right away?

No. Check the wiring and connector first, because an intermittent fault is more often a bad connection than a failed sensor.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.