Engine

P0393 — Camshaft Position Sensor B (Bank 2) Circuit High Input

Severity: medium Drive with care, to a shop

What P0393 means

The engine control unit uses the camshaft position sensor B on bank 2 to learn valve timing, which it needs to time fuel injection and spark. P0393 sets when the voltage in that sensor circuit stays higher than expected. Typical causes are a short to voltage, an open circuit, a failed sensor or, rarely, a faulty control unit.

Symptoms

  • Check Engine light on
  • Rough idle or fluctuating RPM
  • Hesitation or poor acceleration
  • Engine stalling, especially at idle
  • Hard starting or no-start
  • Worse fuel economy

Possible causes

  1. Failed camshaft position sensor B (bank 2)
  2. Damaged wiring or connector: chafed insulation, broken wires
  3. Signal wire shorted to battery voltage
  4. Corroded or loose terminals at the sensor or PCM connector
  5. Open or poor sensor ground
  6. PCM input circuit fault (rare)
  7. Mechanical timing problem or damaged reluctor wheel (rare)

How to diagnose

  1. Read all codes and freeze frame data, clear the code and see whether it returns immediately or intermittently
  2. Locate sensor B on bank 2 and inspect the sensor, connector and harness for chafing, oil and heat damage
  3. Check connector locking and terminal condition, and clean any corrosion
  4. With a multimeter, check reference voltage, ground and signal at the sensor connector per the factory specs
  5. Test the signal wire for a short to voltage and for an open circuit back to the PCM
  6. Compare the cam signal against the crank signal with a scan tool or scope
  7. Verify cam timing and the reluctor wheel if the electrical side is good
  8. If wiring and sensor test fine, check PCM power and grounds before suspecting the PCM itself

Common fixes

  • Replace camshaft position sensor B
  • Repair or replace the damaged wiring or connector
  • Clean and secure the terminals
  • Reflash or replace the PCM (last resort)
  • Correct cam timing if a mechanical fault is found

Questions and answers

What does P0393 mean?

It means the PCM detects a high voltage signal in the camshaft position sensor B circuit on bank 2. A short to voltage or a failed sensor is the most common reason.

Can I drive with code P0393?

Only briefly and carefully, to a repair shop. The engine can stall or fail to restart, so don't put off the repair.

Do I always need a new sensor for P0393?

No. Wiring and connector faults are common, so test the circuit first. Replace the sensor only if the circuit is good and the signal is still wrong.

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.