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P0390 Generic (SAE) Basic entry

Camshaft Position Sensor 'B' Circuit

Updated 2026-10-02 · Ignition system & misfires

Severity
Medium
Typical repair cost
60 – 500 EUR
System
Powertrain

What it means

P0390 is defined as "Camshaft Position Sensor 'B' Circuit". the engine control module stores it when the monitored condition for this component or system is outside the limits programmed by the manufacturer.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Flashing or steady check engine light
  • Engine shaking, especially at idle
  • Loss of power under load
  • Fuel smell from the exhaust
  • Risk of catalytic converter damage if ignored

Common causes

  1. Camshaft Position Sensor 'B' Circuit worn, contaminated or out of calibration
  2. Mechanical problem in the system the sensor measures
  3. Air, vacuum or exhaust leak influencing the reading
  4. Wrong or low-quality replacement part
  5. Wiring resistance causing a small voltage offset

How to diagnose

  1. Compare the live Camshaft Position Sensor 'B' Circuit reading with a known-good value or a second sensor at idle and at 2500 rpm
  2. Check for air, vacuum or exhaust leaks that could skew the reading
  3. Inspect the component for contamination and clean it if the design allows
  4. Verify the part number is correct for the engine
  5. Replace the Camshaft Position Sensor 'B' Circuit if the reading remains out of specification

Frequently asked questions

Can I keep driving with P0390?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing P0390 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

P0365

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