P0390 — Camshaft Position Sensor "B" Circuit (Bank 2)

What does P0390 specifically mean?

P0390 identifies a malfunction in the camshaft position sensor "B" circuit for Bank 2. The fault may involve the sensor itself, its wiring and connector, poor grounding, signal interference, or the related reluctor target.

Is it safe to drive a vehicle with P0390?

Driving may be possible if the engine runs smoothly, but P0390 can produce hesitation, power loss, stalling, or a no-start condition. Do not continue driving if P0390 is accompanied by repeated stalls or severe misfire.

Why does my scanner show P0390 even after replacing the sensor?

A replacement sensor will not clear P0390 if the underlying fault is a damaged wire, poor ground, bad connector terminal, or unstable reluctor signal. The complete Bank 2 camshaft position circuit must be tested before the code is cleared.

Does camshaft position sensor "B" always refer to the exhaust camshaft?

Sensor letters and Bank 2 layouts vary by engine design, so sensor "B" should not be identified solely by left or right side. Use the vehicle's wiring diagram and component location information when testing the P0390 circuit.

The engine control unit constantly monitors every sensor and actuator in the engine bay. When something falls outside the expected range, it logs a diagnostic trouble code. P0390 is one of those codes, specifically tied to the camshaft position sensor circuit on the exhaust side of the engine's second bank. In plain terms, P0390 tells you the PCM has spotted something wrong with how it reads or controls camshaft timing on bank 2 — the engine bank that does not contain cylinder number one.

Modern engines use variable valve timing (VVT) to adjust when valves open and close based on RPM, load, and temperature. The camshaft position sensor feeds the PCM a signal that represents the exact rotational position of the camshaft. The computer uses this signal to synchronize fuel injection and ignition timing, and to command the VVT system. When that signal becomes erratic, disappears, or shows values that do not match what the PCM expects, it sets P0390. Typically the code requires the fault to appear across multiple drive cycles before the check engine light activates, though a severe signal loss can trigger it immediately.

Bank 2 refers to the cylinder bank opposite cylinder 1. On V-shaped engines this is the right-hand or left-hand bank depending on the manufacturer. On inline engines there is technically only one bank, but the PCM still labels sensors with bank designations for coding consistency. The freeze frame stored alongside P0390 captures engine speed, load percentage, coolant temperature, and vehicle speed at the moment the fault was detected. Reviewing that snapshot before diving into diagnostics prevents chasing the wrong problem.

Common Symptoms of P0390

• The check engine light illuminates on the dashboard
• Engine idles roughly or feels unstable at low speeds
• Delayed or difficult starting, especially after the engine sits
• Noticeable drop in low-end torque and overall power
• Fuel economy worsens compared to normal driving history
• The engine may stumble or hesitate under acceleration

What Causes P0390?

The root cause of P0390 can originate from several sources, ranging from simple maintenance oversights to mechanical wear:

• The camshaft position sensor itself has failed or its signal has degraded
• Worn or stretched timing chain, or a jumped timing belt, throwing cam-to-crank relationship off
• A faulty or stuck VVT oil control valve preventing proper hydraulic actuation of the phaser
• Low or contaminated engine oil disrupting the hydraulic pressure VVT systems require
• Damaged wiring, corroded connectors, or a damaged reluctor ring on the camshaft
• A worn cam phaser that can no longer hold its commanded position

How to Diagnose P0390

Follow a logical order to avoid unnecessary part replacement:

1. Connect an OBD2 scanner and confirm P0390 is stored. Record the freeze frame data before clearing anything — those recorded conditions are the recipe for recreating the fault.
2. Check for any related diagnostic trouble codes. Codes in the P0300 range (misfires) or other VVT-related codes often point toward the true underlying problem rather than the sensor itself.
3. Perform a visual inspection of the wiring harness and connector at the camshaft position sensor. Look for frayed wires, broken insulation, moisture intrusion, or loose pins. A poor electrical connection can mimic a failed sensor.
4. Verify engine oil level and condition. VVT systems depend on clean oil at the correct pressure. Dark, sludgy oil or a low oil level can cause VVT malfunctions that set P0390 even when the sensor is good.
5. Scope or graph the camshaft position sensor signal while the engine runs. Compare the waveform against specifications. A weak, noisy, or missing signal indicates sensor failure or a damaged reluctor ring.
6. Clear the code and perform a complete drive cycle that replicates the freeze frame conditions (same RPM, load, and temperature). If P0390 returns, the fault is confirmed and components should be tested or replaced based on findings.

Repair Options and Costs

Prices below reflect typical U.S. independent shop labor and parts rates. Shop around — rates vary by region and vehicle make.

• Replace the camshaft position sensor: parts and labor run $120–$350
• Replace the VVT oil control valve: parts and labor run $200–$500
• Timing chain or belt repair including tensioner and related components: parts and labor run $800–$2,500

Total Cost to Fix P0390

Depending on which component is actually at fault, total repair costs for P0390 typically fall between $120 and $2,500. The least expensive fix — swapping a faulty sensor — can resolve the issue for a few hundred dollars. The most expensive scenario involves timing chain replacement, which requires significant labor. The key takeaway: proper diagnosis before purchasing parts almost always saves money. Most shops will charge a one-hour diagnostic fee to investigate the code properly, which is a worthwhile investment before committing to major repairs.

Can You Drive with P0390?

Proceed with caution. P0390 indicates the PCM cannot reliably determine camshaft position, which disrupts variable valve timing and can force the engine into a reduced-power failsafe mode. If jumped timing or a failed phaser is the underlying cause, continued operation on an interference engine risks contact between valves and pistons — a costly outcome. Address the code before any extended trip, and monitor engine performance closely if the vehicle must be moved a short distance to a repair facility.