P0393 – Camshaft Position Sensor “B” Circuit High Bank 2

P0393 is a diagnostic trouble code that points to a problem with the camshaft position sensor “B” on Bank 2, specifically an intermittent or weak signal. In plain terms, your engine computer is losing track of one of the camshafts on one side of the engine. This can cause hard starts, misfires, poor fuel economy, and sometimes stalling. While it’s not usually an immediate engine killer, you shouldn’t ignore it. In this guide, you’ll learn what P0393 means, common causes, symptoms, and how you or your mechanic can diagnose and fix it correctly.

What Does P0393 Mean?

P0393 stands for “Camshaft Position Sensor ‘B’ Circuit Intermittent (Bank 2).” Bank 2 is the side of the engine that does not contain cylinder #1, and sensor “B” usually refers to the exhaust camshaft sensor on that bank (on most modern engines). “Intermittent” means the signal from that sensor is cutting in and out or is outside the expected voltage range at times.

The ECU uses camshaft position data to control ignition timing, fuel injection, and variable valve timing (VVT). When the signal from the Bank 2, sensor B cam sensor becomes unstable, the ECU can’t accurately sync the cam and crank, so it sets P0393 and may also limit performance to protect the engine.

Quick Reference

• Code: P0393
• Meaning: Camshaft Position Sensor “B” Circuit Intermittent (Bank 2)
• Typical Issue: Failing cam sensor, wiring fault, or connector problem
• Severity: Moderate – can affect drivability and starting
• Common Fix: Replace cam sensor, repair wiring/connector, clear codes

Real-World Example / Field Notes

In the shop, I often see P0393 on higher-mileage V6 and V8 engines with dual overhead cams. A typical case: a customer comes in with a check engine light, rough idle when hot, and occasional long cranking. Scan shows P0393 and sometimes a related cam/crank correlation code. Wiggle-testing the harness to the Bank 2 exhaust cam sensor makes the engine stumble and the scan tool shows the cam signal drop out. In that situation, the fix is usually a new cam sensor and repairing a brittle or oil-soaked connector, followed by a road test and verification with live data.

Symptoms of P0393

• Check engine light on: The MIL/SES light is usually the first thing you notice.
• Hard starting: Long crank time or needing to crank twice before the engine fires.
• Rough idle: Unstable idle speed, shaking, or occasional stalling at stops.
• Loss of power: Noticeable lack of acceleration, especially at low RPM or when hot.
• Poor fuel economy: More frequent fuel stops due to incorrect timing and mixture.
• Engine misfire or hesitation: Jerking, stumbling, or hesitation when you step on the gas.
• VVT-related noise or sluggishness: Variable valve timing may not advance/retard correctly.

Common Causes of P0393

Most Common Causes

• Failed camshaft position sensor “B” (Bank 2): Internal electronics break down with age, heat, and vibration, causing intermittent output.
• Damaged or corroded sensor connector: Loose pins, green corrosion, or oil intrusion at the connector interrupt the signal.
• Wiring issues in the sensor circuit: Chafed, pinched, or broken wires between the cam sensor and ECU cause intermittent voltage or open circuits.
• Oil contamination on the sensor tip: Sludge or metal particles can interfere with the sensor’s ability to read the camshaft tone wheel.
• Incorrect or low-quality replacement sensor: Cheap aftermarket sensors can provide weak or unstable signals that trigger P0393.

Less Common Causes

• Timing chain/belt stretch or misalignment: Excessive slack or incorrect timing can cause erratic cam signals and correlation faults.
• Damaged camshaft tone ring/reluctor: Bent, cracked, or missing teeth on the reluctor wheel produce intermittent readings.
• ECU (PCM) internal fault: Rare, but a failing engine computer can misread a good sensor signal.
• Oil pressure or VVT system issues: If VVT actuators stick or oil passages clog, the camshaft may move unpredictably, confusing the ECU.
• Previous engine work errors: Incorrectly routed wiring, wrong sensor installed, or mis-timed cams after repairs.

Diagnosis: Step-by-Step Guide

You’ll want a basic scan tool (preferably one that shows live data), a digital multimeter, and access to wiring diagrams. A lab scope is ideal but not mandatory for most DIY checks. Having a service manual or reliable online repair info for your specific vehicle is also very helpful.

1. Confirm the code and check for companions. Scan the ECU for P0393 and any related codes such as other cam/crank or VVT codes. Write them down; they help narrow the cause.
2. Inspect the cam sensor location. Find Bank 2 sensor “B” (usually exhaust side on Bank 2). Look for oil leaks, damaged harnesses, or anything rubbing against the wiring.
3. Check the connector closely. Unplug the sensor and inspect for bent pins, corrosion, oil inside the plug, or loose terminals. Clean and repair as needed.
4. Perform a wiggle test. With the engine idling and a scan tool monitoring cam sensor data (or RPM stability), gently wiggle the harness and connector. If the engine stumbles or the reading drops out, you’ve likely found a wiring or connector fault.
5. Test sensor power and ground. Using a multimeter, verify that the sensor has proper reference voltage (often 5V) and good ground according to the wiring diagram. A missing power or ground points to wiring or ECU issues.
6. Check sensor signal circuit. Back-probe the signal wire and look for a fluctuating voltage as the engine cranks or runs. If power and ground are good but the signal is dead or erratic, the sensor is likely bad.
7. Compare Bank 1 and Bank 2 data. If your scan tool supports it, compare camshaft position or VVT data between banks. A big difference on Bank 2 sensor B indicates a local problem with that sensor or its wiring.
8. Inspect timing components if needed. If the sensor and wiring test good but P0393 persists, inspect the timing chain/belt and cam reluctor wheel for damage, stretch, or misalignment.
9. Clear codes and road test. After repairs, clear the codes and perform a road test under various conditions (idle, light throttle, highway). Re-scan for codes and verify that P0393 does not return.

Pro tip: On some vehicles you can use Mode $06 data to see cam/crank correlation test results. This can help confirm a borderline sensor or timing issue before you start replacing parts.

Possible Fixes & Repair Costs

Most repairs for P0393 revolve around restoring a clean, stable camshaft position signal. Depending on what you find during diagnosis, the fix may be simple or more involved.

• Replace Bank 2 camshaft position sensor “B”: The most common repair. Parts typically range from $40–$180 depending on brand and vehicle, plus 0.5–1.5 hours labor.
• Repair or replace damaged wiring/connector: Splicing in a new pigtail, repairing broken wires, or cleaning corrosion. Expect $80–$250 depending on severity and access.
• Fix oil leaks contaminating the sensor: Valve cover gasket or cam seal repairs can run $150–$500+ depending on engine layout.
• Timing chain/belt or VVT repairs: If timing components are worn or misaligned, costs can jump to $600–$1,800+ due to parts and labor.
• ECU replacement/reprogramming (rare): Typically $600–$1,500 including programming if the ECU is confirmed faulty.

In most cases, you’re looking at $150–$450 total at a typical shop for sensor and wiring-related fixes. Costs vary with vehicle make, engine design, part quality (OEM vs aftermarket), and how difficult the sensor is to access.

Can I Still Drive With P0393?

Usually you can still drive with P0393 for a short time, but it’s not ideal. Many vehicles will run in a default or “limp” strategy, which can reduce power and fuel economy. If the signal becomes worse, you may experience stalling, hard starting, or misfires that could leave you stranded. If the engine is running roughly, stalling, or the check engine light is flashing, you should avoid driving and have it towed to prevent further damage.

What Happens If You Ignore P0393?

Ignoring P0393 can lead to chronic hard starting, poor fuel economy, and increased wear on the engine and catalytic converters from misfires or incorrect timing. If the underlying issue is a timing chain, VVT, or wiring problem, it can eventually cause more serious engine damage or leave you stuck when the sensor signal fails completely. Addressing the code early usually keeps the repair simpler and cheaper.

Related Sensor Camshaft Codes

Compare nearby sensor camshaft trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P0368 – Camshaft Position Sensor “B” Circuit High Bank 1
• P0338 – Crankshaft Position Sensor “A” Circuit High
• P0388 – Crankshaft Position Sensor “B” Circuit High
• P0808 – Clutch Position Sensor Circuit High
• P2963 – Intake Air Metering Control Valve Position Sensor Circuit High
• P2616 – Camshaft Position Signal Output Circuit High

Key Takeaways

• P0393 means the ECU is seeing an intermittent signal from the Bank 2 camshaft position sensor “B,” usually the exhaust cam sensor.
• Common causes are a failing cam sensor, wiring or connector problems, or oil contamination at the sensor.
• Symptoms include a check engine light, hard starting, rough idle, loss of power, and poor fuel economy.
• Diagnosis involves checking wiring, connectors, sensor power/ground, and comparing live data between banks.
• Most repairs are relatively affordable if addressed early, typically involving sensor or wiring replacement.

Vehicles Commonly Affected by P0393

P0393 is most common on multi-bank engines (V6 and V8) with dual cam sensors per bank. You’ll frequently see it on:

• Ford and Lincoln 3.5L and 3.7L V6, 5.0L V8, and EcoBoost engines with VVT.
• GM/Chevrolet V6 and V8 engines, including some Silverado, Sierra, Camaro, and SUV models.
• Dodge/Chrysler/Jeep/Ram Pentastar V6 and HEMI V8 engines.
• Hyundai/Kia 3.3L and 3.8L V6 engines with dual overhead cams.
• BMW, Mercedes-Benz, and other European V6/V8s that rely heavily on precise VVT control.

While it can show up on many brands, any engine with a Bank 2 and separate “A” and “B” cam sensors can potentially log P0393.

FAQ

Can I clear P0393 and keep driving if the car feels fine?

You can clear the code, but if the underlying issue isn’t fixed, P0393 will almost certainly come back. Even if the car feels fine now, intermittent cam sensor problems tend to get worse over time and can eventually cause hard starting or stalling. It’s best to diagnose and repair the cause rather than repeatedly clearing the code.

Is P0393 caused by a bad timing chain?

It can be, but that’s less common than a bad sensor or wiring issue. A stretched or mis-timed chain can cause erratic camshaft position readings and related codes, especially if combined with VVT problems. Before condemning the timing chain, always test the sensor, wiring, and connector, and compare live cam/crank data.

How do I know which side is Bank 2 for P0393?

Bank 2 is the side of the engine that does not contain cylinder #1. The exact location depends on engine design and orientation. Your owner’s manual, service manual, or a reliable repair database will show which side is Bank 2. Getting this right is important so you don’t replace the wrong sensor.

Can a bad camshaft sensor damage my engine?

By itself, a bad camshaft sensor usually doesn’t physically damage the engine, but it can cause poor running, misfires, and rich or lean conditions. Over time, that can stress the catalytic converters and other components. If the engine starts running very rough or the check engine light flashes, continuing to drive can lead to more serious damage.

Do I need OEM parts to fix P0393?

Using an OEM or high-quality aftermarket cam sensor is strongly recommended. Cheap sensors are a common cause of repeat camshaft codes, including P0393. For wiring repairs, use automotive-grade wire and sealed connectors. Spending a little more on quality parts up front usually prevents headaches and repeat repairs later.