P0397 – Meaning, Symptoms, Causes & How to Fix It

P0397 is an OBD-II trouble code that points to a problem with the rear (Bank 2) camshaft position sensor circuit on your engine. In plain terms, your ECU is seeing a low or weak signal from that sensor, which can throw off valve timing and affect how smoothly your engine runs. While this code usually won’t leave you stranded immediately, it can cause drivability issues and long-term damage if ignored. In this guide, you’ll learn what P0397 means, common symptoms, causes, and how you or your mechanic can diagnose and fix it.

What Does P0397 Mean?

P0397 stands for “Camshaft Position Sensor ‘B’ Circuit Low (Bank 2).” Bank 2 is the side of the engine that does not contain cylinder #1, and sensor “B” typically refers to the exhaust camshaft sensor on that bank (though exact naming can vary by manufacturer). The “circuit low” part means the ECU is detecting a voltage or signal that is lower than the expected range.

The camshaft position sensor tells the ECU where the camshaft is in relation to the crankshaft. The ECU uses this data for variable valve timing, fuel injection timing, and ignition timing. When the signal is too low, the ECU can’t trust that information, so it sets P0397 and usually turns on the check engine light.

Quick Reference

Code: P0397
Definition: Camshaft Position Sensor “B” Circuit Low (Bank 2)
Severity: Low to moderate – drivability issues possible
Common Causes: Bad cam sensor, wiring faults, poor connections, oil contamination
Typical Fixes: Replace cam sensor, repair wiring, clean connectors, address oil leaks

Real-World Example / Field Notes

In the shop, I see P0397 most often on higher-mileage engines with variable valve timing. A typical case: a V6 SUV comes in with a check engine light, slightly rough idle, and occasional hesitation. Scan tool shows P0397 and maybe a related cam timing code. The owner says the valve cover has been “sweating” oil for months. Pulling the Bank 2 exhaust cam sensor reveals the connector soaked in oil and the sensor tip contaminated. After cleaning the connector, repairing a brittle wire, and installing a new OEM sensor, the engine smooths out and the code never returns.

Symptoms of P0397

Check engine light on: The MIL will almost always illuminate when P0397 is stored.
Rough idle: You may feel the engine shaking or idling unevenly, especially when warm.
Hesitation or stumble: Acceleration can feel flat, jerky, or delayed due to incorrect timing.
Reduced power: Loss of performance, especially at low to mid RPM, as cam timing is limited.
Poor fuel economy: Incorrect cam timing can cause the engine to burn more fuel than normal.
Hard starting: Extended cranking or needing to press the gas pedal to start in some cases.
Intermittent stalling: In more severe cases, the engine may stall at stops or when shifting into gear.

Common Causes of P0397

Most Common Causes

Failed camshaft position sensor (Bank 2, sensor B): Internal electronic failure or wear can cause a weak or low signal.
Damaged wiring to the sensor: Chafed, brittle, or broken wires near the valve cover or engine harness are very common.
Corroded or oil-soaked connector: Oil leaks from valve covers or VVT solenoids can wick into the connector and cause signal issues.
Poor electrical ground or power feed: High resistance in the sensor’s ground or reference voltage line will register as a low circuit condition.

Less Common Causes

Internal ECU fault: Rare, but a failing engine control unit can misread or misdrive the sensor circuit.
Timing chain or belt issues: Excessive slack or misalignment can cause erratic sensor readings, sometimes triggering circuit-related codes.
Aftermarket remote start or alarm wiring: Poorly spliced wiring near the engine harness can interfere with the sensor signal.
Incorrect sensor type installed: Using the wrong part number or cheap aftermarket sensor can cause low signal amplitude.

Diagnosis: Step-by-Step Guide

You’ll want a basic scan tool, a digital multimeter (DMM), and ideally a wiring diagram for your specific vehicle. An advanced scan tool that can read live data and Mode $06 information makes diagnosis easier, but you can still do a lot with basic tools. Always work on a cool engine when possible and disconnect the battery if you’re opening harnesses.

Confirm the code and check for companions: Use a scan tool to read all stored and pending codes. Look for related camshaft or crankshaft sensor codes (like P0390–P0394). Clear codes and see which ones return first.
Inspect the sensor location: Find Bank 2, sensor B (usually the exhaust cam on Bank 2). Visually inspect the sensor body, connector, and nearby wiring for oil leaks, broken insulation, or physical damage.
Check the connector: Unplug the connector and look for corrosion, bent pins, oil intrusion, or loose terminals. Clean with electrical contact cleaner and allow it to dry before reconnecting.
Verify power and ground: With the key on (engine off), use your multimeter to check for the proper reference voltage (often 5V) and a good ground at the sensor connector. Compare to a wiring diagram or service information for your vehicle.
Measure sensor signal (if possible): Some sensors output a digital square wave, others a Hall-effect signal. With the engine cranking or running, back-probe the signal wire and look for changing voltage. A flat, low reading points to a bad sensor or wiring issue.
Wiggle test the harness: While monitoring live data or voltage, gently move the wiring harness around the sensor and along the route to the ECU. If the signal drops out or changes, you likely have an internal break or poor connection.
Check for oil leaks and contamination: Look around valve covers, VVT solenoids, and the sensor bore for oil leaks that may be wicking into the connector. Oil inside the connector can cause a low circuit condition.
Swap sensors (if identical): On some engines with multiple identical cam sensors, you can swap Bank 1 and Bank 2 sensor B. If the code moves to the other bank, the sensor itself is bad.
Review Mode $06 and freeze-frame data: If your scan tool supports Mode $06, check for borderline cam sensor test results. Freeze-frame data helps you see RPM, load, and temperature when the code set, guiding further testing.
Rule out ECU problems: Only after confirming good wiring, power, ground, and sensor operation should you suspect an ECU fault. This usually requires professional-level diagnostics.

Pro tip: Many cam sensor codes come back quickly after clearing if the sensor is truly bad. If P0397 only appears intermittently, focus on wiring movement, heat-related issues, and oil contamination before throwing parts at it.

Possible Fixes & Repair Costs

Repairs for P0397 range from simple connector cleaning to sensor replacement or wiring repair. A new camshaft position sensor typically costs $40–$150 for the part, plus 0.5–1.5 hours of labor depending on access. Wiring repairs can run $100–$300 if the harness needs splicing or connector replacement. In rare cases where the ECU is faulty, you might see $600–$1,200 including programming. Overall, most P0397 fixes land in the $150–$450 range at a typical independent shop, depending on your vehicle, labor rates, and parts quality (OEM vs aftermarket).

Can I Still Drive With P0397?

In most cases, you can still drive with P0397 for a short period, especially if the only symptom is a check engine light and mild roughness. However, you may notice reduced performance, poor fuel economy, and occasional hesitation. If the engine starts stalling, misfiring heavily, or struggling to start, you should avoid driving and get it checked immediately. It’s best to schedule diagnosis and repair soon rather than waiting, because prolonged operation with incorrect cam timing can accelerate wear on valvetrain components and catalytic converters.

What Happens If You Ignore P0397?

Ignoring P0397 can turn a relatively simple sensor or wiring repair into bigger problems. The ECU may run the engine in a default or “limp” timing strategy, which hurts fuel economy and performance. Over time, poor combustion can foul spark plugs, stress the timing components, and overheat the catalytic converters, leading to much more expensive repairs. Addressing the code early is usually far cheaper than dealing with the long-term consequences.

Last updated: March 1, 2026

Key Takeaways

P0397 indicates a low or weak signal from the Bank 2, sensor B camshaft position sensor circuit.
Common causes include a bad sensor, wiring damage, poor connections, and oil contamination at the connector.
Symptoms range from a simple check engine light to rough idle, hesitation, and reduced power.
Diagnosis involves checking power, ground, and signal at the sensor, as well as inspecting wiring and connectors.
Most repairs are relatively affordable if handled early, typically involving sensor replacement or wiring repair.

Vehicles Commonly Affected by P0397

P0397 shows up most often on engines with dual overhead cams and variable valve timing. You’ll commonly see it on V6 and V8 models from manufacturers like Nissan/Infiniti, Hyundai/Kia, GM (Chevrolet, GMC, Cadillac), Ford, and some European brands such as BMW and Mercedes-Benz. Many crossovers, SUVs, and trucks with DOHC V6 engines are frequent visitors to the shop with this code. High-mileage vehicles, or those with known valve cover oil leak issues, are especially prone to cam sensor circuit problems like P0397.

FAQ

Can I clear P0397 and keep driving without fixing it?

You can clear the code, but if the underlying problem is still there, P0397 will almost always come back. Clearing it temporarily turns off the check engine light, but it doesn’t fix the sensor or wiring issue. It’s fine to clear the code after repairs to confirm the fix, but relying on clearing alone isn’t a solution.

Is P0397 serious enough to fail an emissions test?

Yes, in most areas a lit check engine light and stored P0397 will cause an automatic emissions test failure. The ECU may also disable some readiness monitors when this code is active. You’ll need to repair the issue, clear the code, and drive enough for the monitors to reset before retesting.

How do I know if the camshaft sensor or the wiring is bad?

You need to test both. If the sensor has proper power and ground and the signal is still low or flat, the sensor is likely bad. If power or ground is missing, or the signal changes when you wiggle the harness, the wiring or connector is suspect. Swapping sensors side-to-side (when possible) is another good way to confirm a bad sensor.

Can low oil level cause P0397?

Low oil level by itself usually won’t cause a “circuit low” code, but it can affect variable valve timing operation and lead to related cam timing codes. However, oil leaks from valve covers or VVT components can contaminate the cam sensor connector, which may trigger P0397. So oil issues can be indirectly related.

Do I need an OEM camshaft sensor, or is aftermarket okay?

Many aftermarket sensors work fine, but on some engines the ECU is picky about signal quality. If you install a cheap sensor and the code returns quickly, or new driveability issues appear, switch to an OEM or high-quality brand. In my experience, spending a bit more on a good sensor often saves time and repeat repairs.

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