OBD-II Code P0390: Camshaft Position Sensor 'B' Circuit - Bank 2

What Does P0390 Mean?

Code P0390 means the Powertrain Control Module (PCM) lost the signal from the Camshaft Position Sensor 'B' for Bank 2. This sensor tracks the exact rotational position of the exhaust camshaft. Without this data, the PCM cannot control variable valve timing, ignition timing, or fuel injection, causing severe performance issues.

Technical definition: The official SAE/OBD-II definition is "Camshaft Position Sensor 'B' Circuit Malfunction (Bank 2)". This indicates the PCM detects an incorrect, missing, or erratic voltage signal from the camshaft position sensor designated 'B' on the engine's second bank. The 'B' sensor monitors the exhaust camshaft, while the 'A' sensor monitors the intake camshaft.

Can I Drive With P0390?

Yes, But With Caution. You can drive for short, essential trips, but the engine will likely run rough, stall unexpectedly, or be hard to start. This is a high-priority repair. Prolonged driving with this fault, especially with misfires, dumps unburnt fuel into the exhaust and destroys the catalytic converter—a $1,500 to $4,000 repair. Fix the vehicle immediately to avoid stranding or expensive secondary damage.

Common Causes

• Faulty Camshaft Position Sensor (Very Common) — The sensor itself is the most frequent point of failure. Internal electronics wear out over time or become contaminated by engine oil, causing it to send a weak, incorrect, or dead signal.
• Low Engine Oil Level or Pressure (Common) — Modern engines with Variable Valve Timing (VVT) rely on oil pressure to adjust camshaft timing. Low oil levels or pressure prevent the VVT system from operating, directly triggering camshaft sensor codes.
• Wiring Harness or Connector Issues (Common) — Wiring leading to the sensor becomes damaged, corroded, or loose. Oil leaks from a valve cover or oil cooler frequently contaminate the connector and short the signal. Wires also chafe against other components or become brittle from heat.
• Poor Quality Aftermarket Sensors (Common) — Using a low-quality aftermarket sensor causes repeat failures. These parts have incorrect internal variances and fail quickly, causing the code to return immediately. Use an OEM sensor to prevent this.
• Timing Component Problems (Less Common) — A stretched timing chain, worn belt, failing tensioner, or faulty VCT solenoid alters the camshaft's actual position relative to the sensor. This triggers P0390, often accompanied by timing codes like P0021 or P0022.
• Damaged Reluctor Wheel / Tone Ring (Rare) — The sensor reads a toothed wheel (reluctor ring) on the camshaft. If this wheel cracks or shifts position, the sensor generates an incorrect signal, triggering P0390 even if the sensor and wiring are perfect.
• Failed or Outdated PCM (Rare) — The vehicle's main computer fails and cannot process the sensor signal, or the PCM software contains a calibration error requiring a manufacturer update. This is the last item to check after eliminating all physical faults.

Symptoms

• Check Engine Light is On — The Malfunction Indicator Lamp (MIL) illuminates on the dashboard.
• Engine is Hard to Start or Won't Start — The engine cranks for an extended period before starting, or fails to start entirely because the PCM lacks the camshaft position data required for ignition timing.
• Rough Idle and Stalling — The engine runs unevenly, shakes at a stop, or shuts off unexpectedly while driving or idling.
• Reduced Engine Power and Hesitation — The vehicle feels sluggish and has poor acceleration because engine timing is not optimized. The PCM intentionally limits power ('limp mode') to prevent damage.
• Worse Fuel Economy — The engine runs inefficiently without correct camshaft data, causing a 10% to 20% drop in fuel economy.
• Audible Engine Noise (Ticking/Rattling) — On engines like the Jeep 3.6L Pentastar, a P0390 code accompanied by a loud ticking sound indicates a failing rocker arm destroying the camshaft.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Replace the Camshaft Position Sensor (Bank 2, Sensor 'B') — Parts: $40-$110 for an OEM sensor, Labor: $135-$200, depending on accessibility, ~1.2 hr book time (DIY)
• Correct Engine Oil Level or Replace Leaking Gaskets (e.g., Valve Cover, Oil Cooler) — Parts: $30-$150 for gaskets/oil, Labor: $200-$600+, depending on gasket location, ~4 hr book time (Intermediate)
• Repair or Replace Damaged Wiring or Connector — Parts: $10-$50 for a new pigtail connector or wiring supplies, Labor: $125-$350, depending on the location and extent of damage, ~2 hr book time (Intermediate)
• Replace Camshaft Phaser or VCT Solenoid — Parts: $100-$400 per phaser/solenoid, Labor: $200-$800+ per solenoid, as this is a more involved mechanical repair, ~2.5 hr book time (Professional)
• PCM Reprogram or Replace — Parts: $0 (reprogram) - $1,000+ (replacement), Labor: $100-$300 for reprogramming or installation, ~1.5 hr book time (Professional)

Used vs. New Parts: Buying Guide

When a used part is worth it: For a critical, low-cost electronic part like a camshaft position sensor, buying used is never recommended. The risk of receiving a part that is already failing or has a short lifespan is very high, and the cost savings are minimal compared to the repeat labor cost.

Donor quality checklist:

• Avoid used sensors entirely. There is no reliable way to gauge the remaining life of a used electronic sensor.
• If buying aftermarket, stick to well-known Tier 1 suppliers like Bosch, Denso, Delphi, or NTK.
• Always favor a new OEM (Original Equipment Manufacturer) part, as they are built to the vehicle's exact specifications and have a much lower failure rate.

Decision logic:

• If The part is an electronic sensor like a camshaft position sensor → Buy a new OEM or Tier-1 aftermarket part. Do not buy used.
• If The cost of a new OEM sensor is less than double the labor cost to replace it → Buy the new OEM part. The cost of a potential repeat failure with a cheap part outweighs the savings.
• If You are forced to choose between a no-name online part and a used OEM part → Neither is a good option, but the used OEM part is a slightly lesser risk than a known-unreliable new part.

Warranty tradeoff: Used parts from a salvage yard typically offer a 30-90 day warranty, if any. Cheap aftermarket parts have a limited warranty but are known for high failure rates. A new OEM part typically carries a 12-month/12,000-mile warranty and the highest assurance of quality.

Worst-case if a used part fails: $200-$400 if a cheap or used part fails after installation, representing the cost of a second diagnostic fee, repeat labor, and the purchase of a quality part.

What Happens If You Wait — Timeline

1. 0-1 month: Check Engine Light is on. You notice a slightly harder start or a brief rough idle when cold, but there are no major drivability symptoms. (MPG impact: 0-5%% · Added cost: $0-$50 in wasted fuel)
2. 1-3 months: Symptoms become consistent. The engine hesitates during acceleration, idles roughly, and stalls at stoplights. Fuel economy drops noticeably. Stalling in traffic becomes a severe safety risk. (MPG impact: 5-10%% · Added cost: $50-$150 in wasted fuel)
3. 3-6 months: Persistent misfires develop. Incorrect timing and excess unburnt fuel overheat the catalytic converter. You smell raw gasoline from the exhaust. The converter's internal substrate cracks and degrades. (MPG impact: 10-20%% · Added cost: $300-$800 (catalytic converter damage is now likely))
4. 6+ months: Catastrophic failure of the catalytic converter. The substrate melts, clogging the exhaust. The engine suffers severe power loss and cannot accelerate above 30 mph. Guaranteed emissions test failure. (MPG impact: 20-30%+% · Added cost: $1,500-$4,000+ (for catalytic converter replacement and potential O2 sensor damage))

Cost of Not Fixing It

• 0-1 month: Noticeable drop in fuel economy by 5-10%, rough idling, and potential stalling in traffic, creating a safety hazard. (Added cost: $20-$60 in wasted fuel)
• 1-6 months: Persistent misfires from incorrect timing cause unburnt fuel to enter the exhaust, overheating and destroying the catalytic converter substrate. (Added cost: $1200-$2800 for catalytic converter replacement)
• 6+ months: Complete catalytic converter failure, guaranteed emissions test failure, and severe engine wear due to inefficient operation. In extreme cases with related mechanical failures (e.g., Jeep rocker arms), leads to camshaft and cylinder head damage. (Added cost: $2500-$5000+ for catalytic converter and other potential engine repairs)

Diagnosis Steps

1. Read the Trouble Codes
   Use an OBD-II scanner to confirm P0390 is present and check for related codes (e.g., P0345, P0021, P0394). Note the freeze-frame data showing the engine's operating conditions when the code set.
   Tools: OBD-II Scanner (Beginner)
2. Check Engine Oil Level and Condition
   Verify the engine oil is full and clean. Low or dirty oil prevents the VVT system from functioning, which directly triggers camshaft sensor codes on modern vehicles.
   Tools: Dipstick, Paper towel (Beginner)
3. Visually Inspect the Sensor and Wiring
   Locate the Camshaft Position Sensor 'B' on Bank 2. Look for damage to the sensor, connector, and wiring harness. Check for oil contamination from leaking gaskets, corrosion on pins, or chafed wires.
   Tools: Flashlight, Mirror (Beginner)
4. Test the Sensor by Swapping
   If the engine has an identical, accessible sensor on Bank 1, swap the suspect sensor with the known good one. Clear the codes and drive. If the code changes to P0365, the sensor is faulty. If P0390 returns, the problem is in the wiring or PCM.
   Tools: Basic hand tools (socket set, wrenches) (Intermediate)
5. Test the Sensor's Circuit with a Multimeter
   For a 3-wire Hall-effect sensor, disconnect the connector and turn the key 'ON' (engine off). Use a multimeter to verify a 5-volt reference on one wire and a solid ground on another.
   Tools: Multimeter, Vehicle Service Manual (Intermediate)
6. Bench Test the Sensor's Function (Hall-Effect)
   Reconnect the sensor. Back-probe the signal and ground wires with a multimeter set to DC volts. With the key 'ON', the signal wire reads ~5 volts. Pass a metal wrench in front of the sensor tip. The voltage drops to near 0 volts each time the metal passes. If voltage doesn't change, the sensor is dead.
   Tools: Multimeter with back-probes, Metal object (Intermediate)
7. Advanced: Test Circuit Voltage at Connector
   With the sensor unplugged and ignition ON, test the harness connector. The reference wire reads 4.8V - 5.2V. The ground wire shows continuity to chassis ground (near 0 Ohms). The signal wire reads ~5V. Readings outside these ranges confirm a wiring or PCM issue.
   Tools: Multimeter, Vehicle-specific wiring diagram (Advanced)
8. Advanced: Test VCT Solenoid Resistance
   If VCT issues are suspected (common on Fords), unplug the Bank 2 exhaust VCT solenoid and measure internal resistance. For a Ford 5.0L, the spec is 7.0 to 14.0 Ohms. Infinite resistance or an out-of-range reading confirms a failed solenoid.
   Tools: Multimeter, Service Manual (Advanced)
9. Analyze the Signal with an Oscilloscope (Professional)
   Connect an oscilloscope to the sensor's signal and ground wires. A good Hall-effect sensor produces a clean digital square wave toggling between 0V and 5V. A bad sensor shows dropouts or a distorted waveform.
   Tools: Oscilloscope, Back-probes (Professional)
10. Check Mechanical Engine Timing
    If the sensor and circuit are good, the issue is mechanical. Inspect the timing chain, belt, and phasers for correct alignment, tension, and wear. This requires significant engine disassembly.
    Tools: Advanced mechanical tools, Service Manual (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 180-200°F (fully warmed up)
• RPM: 1500-2500 (cruise / steady throttle)
• Engine Load: 30-60% (light to moderate acceleration)
• Vehicle Speed: 35-55 mph (city or highway driving)

Related Codes

• P0394 — P0390 indicates a complete circuit malfunction (no signal), while P0394 means the signal is intermittent or erratic. P0390 points to a dead sensor or broken wire, whereas P0394 suggests a loose connection, chafed wiring that shorts out with vibration, or a sensor beginning to fail.
• P0345 — This code is for the 'A' sensor (intake camshaft) on the same engine bank (Bank 2). P0390 is for the 'B' sensor (exhaust). Seeing both codes together strongly suggests a shared power/ground wire issue in the harness, or a significant mechanical timing problem on Bank 2 (like a jumped timing chain).
• P0021 / P0022 — These are performance codes indicating the Bank 2 camshaft is over-advanced (P0021) or over-retarded (P0022). If a mechanical part like a VCT solenoid or cam phaser fails, it sets both a circuit code and a timing performance code. Address the P0390 circuit fault first; if timing codes remain, mechanical components are the cause.
• P0300 / P0302 — These are misfire codes (P0300 for random, P0302 for cylinder 2). A P0390 fault directly causes misfires. The PCM loses track of the exhaust cam's position, leading to incorrect ignition and injection timing, causing misfires on Bank 2. Always diagnose and fix P0390 first to resolve subsequent misfire codes.

Climate & Environmental Factors

• Extreme Heat: Prolonged exposure to high engine temperatures degrades the sensor's internal electronics and plastic housing, leading to premature failure. This is a common cause of wear-and-tear failure.
• Humidity and Moisture: High humidity or direct water intrusion (from driving through water or engine washing) causes moisture to seep into the sensor or its connector. This leads to corrosion on the electrical pins and short circuits, disrupting the signal.

How to Talk to a Mechanic About This Code

Say this: "I have an OBD-II code P0390 for the Camshaft Position Sensor 'B' on Bank 2. I'd like to schedule a diagnostic appointment. Please start by checking the engine oil level, inspecting the sensor's electrical connector, and checking the wiring for damage or oil contamination before recommending a part replacement."

This signals to the shop that you understand the root cause isn't always a bad sensor. It directs them to perform a thorough diagnosis, checking for common, less expensive issues like wiring damage or oil leaks first, preventing unnecessary parts replacement.

Avoid saying:

• 'My check engine light is on, can you just fix it?'
• 'I'm pretty sure it's a bad sensor, just replace it.'
• 'Do whatever you think is best.'

Questions to ask before authorizing the repair:

• Did you test the sensor's signal directly, for example by swapping it with the sensor from Bank 1?
• Did you find any oil leaks from the valve cover or oil cooler that contaminated the connector?
• Was the wiring harness inspected for chafing or damage, especially near the steering shaft on a Jeep?
• What brand of replacement sensor are you planning to use? Is it an OEM part?
• What is the warranty on both the part and the labor for this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended if a known TSB applies or if initial diagnostics at an independent shop are inconclusive. Also the best choice for warranty claims.
  Best for: Vehicles still under powertrain warranty., Known manufacturer-specific issues, like a Ford VCT solenoid TSB or a Jeep rocker arm failure., Complex electrical issues or when a PCM software update is required.
  Downsides: Typically the highest labor rates ($150-$250/hr)., Recommends larger assembly replacements when a smaller component fix is possible. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for most P0390 repairs. A reputable independent shop easily handles sensor replacement, wiring repair, and related gasket jobs at a lower cost than a dealer.
  Best for: Out-of-warranty vehicles where the cause is likely a sensor, wiring, or oil leak., Cost-conscious owners who have a trusted local mechanic., Most common P0390 scenarios.
  Downsides: Quality and diagnostic capabilities vary; look for ASE certifications and Google reviews above 4.5 stars., Lacks access to the very latest manufacturer TSBs or specialized programming tools. (Typical cost: +0% vs. baseline)
• Chain Shop: Use with caution. Acceptable if you are certain the sensor itself has failed, but AVOID for initial diagnosis, as they miss the true root cause like a wiring issue or a VCT solenoid problem.
  Best for: Simple, clear-cut sensor replacements where you have already confirmed the sensor is the fault.
  Downsides: Technicians lack the experience for in-depth electrical or mechanical diagnosis required for P0390., High pressure to sell parts leads to replacing the sensor without diagnosing underlying wiring or mechanical faults. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the total estimated repair cost exceeds 40-50% of your car's private-party value (from a source like Kelley Blue Book), you should seriously consider selling or trading in the vehicle instead of repairing it.

• Car worth $5000, fix is $2500: Walk away. The repair cost is 50% of the car's value, and for an issue that involves timing components, other age-related failures are likely to follow.
• Car worth $15000, fix is $1200: Fix it. The repair cost is well below the threshold and restores a critical engine function.
• Car worth $3000, fix is $2000: Walk away. The repair cost is two-thirds of the car's value. It is not a sound financial decision.

What Scan Tool You Need for This Code

Minimum: A scanner that reads and clears codes, and critically, displays live sensor data.

A $20 code reader only tells you the P0390 code is present. It cannot show you if the sensor is producing a signal at all, if the signal is intermittent, or if it's out of sync with other sensors. To diagnose P0390 effectively, you need to see the live data stream from the camshaft position sensor to determine if the fault is with the sensor, the wiring, or a mechanical issue.

Budget: BlueDriver Pro or Ancel BD310 (~$90) — These Bluetooth scanners connect to a smartphone app to read/clear codes, view freeze-frame data, and display live data streams. You can graph the camshaft sensor's output to look for dropouts or an absent signal, which is essential for diagnosing P0390.

Mid-range: Foxwell NT510 Elite or Innova 5610 (~$150) — These handheld scanners offer advanced features, including manufacturer-specific codes and data. The Innova 5610 features extensive live data capabilities and records it. They offer basic bidirectional controls to test components like VCT solenoids, which cause P0390.

Professional: Autel MaxiCOM MK808 or XTOOL D7S (~$500) — Provides full bidirectional control to actively test sensors and solenoids. These tools perform system-wide network scans (topology mapping) and initiate procedures like a camshaft position sensor relearn if required by the vehicle after replacement.

Rent vs buy: For a one-time diagnosis, major auto parts stores like AutoZone or O'Reilly offer a free tool loaner program where you borrow a basic OBD-II scanner. However, these loaner tools lack live data graphing. If you plan to do your own car maintenance, buying a budget pick like a BlueDriver is a worthwhile investment.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the fault code
2. Perform at least one complete drive cycle to allow the vehicle's readiness monitors to run
3. Rescan for codes to confirm the fix was successful

Drive cycle (~30 minutes): A general drive cycle involves: 1) Cold start (let vehicle sit 8+ hours). 2) Idle for 2-3 minutes. 3) Drive for 10-15 minutes with mixed city/highway speeds. 4) Hold a steady speed (e.g., 55 mph) for 3-5 minutes. 5) Perform a few gentle accelerations and decelerations. 6) Allow the vehicle to cool down.

Readiness monitors affected: Catalyst Monitor, Evaporative System Monitor, Oxygen Sensor Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Simply disconnecting the battery clears the code, but it also resets all readiness monitors, causing an emissions test to fail for being 'not ready'.
• The code immediately returns if the underlying root cause (e.g., bad wiring, faulty VCT solenoid) was not corrected.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An active P0390 code and illuminated Check Engine Light is an automatic failure of the Smog Check. All required readiness monitors must also be in a 'ready' state to pass, requiring a 30-minute drive cycle after repair.
• New York: The NYS vehicle inspection includes an OBD-II scan. An active P0390 fault results in an automatic inspection failure.
• Texas: In counties requiring emissions testing, the OBD-II system check is part of the annual safety inspection. A P0390 code causes the vehicle to fail this inspection.

Most Commonly Affected Vehicles

• Ford F-150, Mustang (2018-2020) — For vehicles with the 5.0L engine, Technical Service Bulletin (TSB 18-2360) indicates this code is caused by a faulty exhaust VCT oil control solenoid, not the sensor itself. Low oil levels also trigger this code. VCT solenoid replacement costs $216-$419 per solenoid.
• Jeep Grand Cherokee, Wrangler (2011-2018) — The 3.6L Pentastar V6 is notorious for this code. Causes range from simple sensor failure to a chafed wiring harness near the steering shaft. Severe causes include failed rocker arms (listen for ticking), faulty cam phasers, or a leaking oil filter/cooler housing dripping oil onto the sensor.
• Ram ProMaster, 1500 (2014-2018) — On the 3.6L V6, a common cause is the oil filter/cooler housing assembly developing cracks and leaking oil directly onto the Bank 2 camshaft sensor and its wiring harness, causing a signal failure.
• Subaru WRX, STI, Forester (2015-2017) — On these models, P0390 is caused by sensor failure or wiring issues. A TSB for the related BRZ/FRS suggests that incorrect sensor-to-tone-ring clearance is a cause, requiring shims to fix.
• BMW Various models with N52, N54, N55 engines (2006-2015) — BMW engines are sensitive to camshaft sensor failures. P0390 points to the exhaust camshaft sensor on Bank 2. Oil leaks from the valve cover gasket are a very common cause, contaminating the sensor.
• Hyundai / Kia Sonata, Elantra, Optima, Sorento (2010-2015) — On some 4-cylinder models with automatic transmissions, the P0390 code is misleadingly triggered by a failing transmission input or output speed sensor due to how the manufacturer implements the generic OBD-II code. On V6 models, it correctly refers to the Bank 2 camshaft sensor.
• Chevrolet Silverado, Camaro (2007-2024) — V8 models experience P0390 due to sensor failure, with wiring damage from heat and vibration also being a contributing factor.
• Land Rover Range Rover, LR4 (2010-2016) — On Land Rover models, outright sensor failure is less common. The first step is checking the wiring connectors for contamination from coolant or other fluids. A common diagnostic trick is swapping the Bank 2 sensor with the Bank 1 sensor to see if the fault code follows the sensor.

Manufacturer-Specific Notes

• Ford: On 2018-2020 models with the 5.0L V8, TSB 18-2360 advises technicians to replace the Bank 2 exhaust VCT oil control solenoid (Part #HL3Z-6M280-A) to fix P0390 and/or P0394, as it is a more likely cause than the sensor itself.
• Chrysler / Dodge / Jeep / Ram: On the 3.6L Pentastar V6, P0390 is frequently a symptom of another issue. A leaking oil filter housing drips oil onto the sensor. The sensor's wiring harness rubs against the steering shaft. Most critically, if a ticking noise is present, suspect a failed rocker arm, which destroys the camshaft.
• Hyundai / Kia: On some 4-cylinder models with automatic transmissions, the P0390 code is misleadingly triggered by a failing transmission speed sensor, due to how the manufacturer's control logic interprets generic OBD-II codes.
• Land Rover: Technicians report that camshaft position sensor failures are relatively rare. The primary diagnostic step is thoroughly inspecting the wiring connectors for fluid contamination (coolant, oil) and then swapping the suspect sensor with its counterpart on Bank 1 to see if the fault migrates.

Real Owner Stories

2018 Ford F-150 5.0L with intermittent stalling

Owner experienced an intermittent check engine light, slightly rough idle, and occasional stalling.

What they tried:

1. The owner planned to replace the camshaft position sensor first.
2. Forum members and TSBs pointed towards a different root cause.

Outcome: The cause for this specific vehicle is a faulty VCT (Variable Camshaft Timing) oil control solenoid, not the sensor. Ford issued Technical Service Bulletin (TSB) 18-2360 for this exact issue, requiring replacement of the VCT solenoid (Part #HL3Z-6M280-A).

Lesson: Always check for vehicle-specific TSBs. For 2018-2020 Ford 5.0L engines, P0390 points to the VCT solenoid, and replacing the sensor will not fix the problem.

2019 Jeep Wrangler (JL) after a botched oil change

Hours after an oil change, the Check Engine Light came on with code P0390. The engine oil pressure was extremely low (8-10 PSI) and the dipstick was dry.

What they tried:

1. The owner initially tried to access the sensor to test or replace it.
2. Upon inspection, they found oil sprayed all over the engine bay.

Outcome: The shop tore the O-ring on the oil filter cap, causing a massive oil leak. The P0390 code was triggered by a lack of oil pressure to the VVT system, not a faulty sensor. After refilling the oil and fixing the leak, the issue was resolved.

Lesson: A trouble code doesn't always mean a bad sensor. If the code appears after recent service, inspect the work performed. Low engine oil is a known cause of VVT-related codes like P0390.

2017 Jeep Wrangler 3.6L with persistent P0390/P0394 codes

For over a year, the owner battled recurring P0390 and P0394 codes that caused performance issues. Multiple shops were unable to find the root cause.

What they tried:

1. Replaced camshaft sensors multiple times (both OEM and aftermarket).
2. Swapped sensors from bank to bank (fault did not move).
3. Replaced the entire engine wiring harness for over $2,000.
4. The problem persisted through all of these attempted fixes.

Outcome: The ultimate cause was a missing oil gallery plug under the driver's side valve cover, a rare mechanical issue on the 3.6L Pentastar engine. This created an internal oil pressure leak that starved the Bank 2 phasers, triggering the codes. Tightening the plugs to 12 ft-lbs resolved the issue completely.

Lesson: If a sensor replacement and wiring check don't fix the code, an underlying mechanical issue is likely. On Pentastar engines, this includes failed rocker arms or missing internal oil gallery plugs.

How to Prevent This Code From Triggering

• Change engine oil every 5,000 to 7,500 miles using the manufacturer-specified viscosity. (Per manufacturer schedule) — Prevents the formation of engine sludge that clogs the fine mesh screens on VVT solenoids and blocks oil passages, ensuring proper VVT operation and preventing oil-starvation codes.
• Repair valve cover and oil cooler leaks immediately. (As needed) — Prevents leaking oil from saturating the camshaft sensor's plastic housing and electrical connector, which degrades the materials and causes a short circuit.
• Install only OEM or Tier-1 aftermarket sensors (Bosch, Denso, NTK) during replacement. (During replacement) — Cheap aftermarket sensors are a leading cause of repeat failures due to incorrect electronic tolerances. OEM sensors ensure reliability and compatibility with the vehicle's PCM.
• Inspect the valvetrain immediately if you hear engine ticking or rattling. (As needed) — On engines like the Jeep 3.6L Pentastar, a ticking noise indicates a failing rocker arm. Addressing this early prevents the rocker from seizing and destroying the camshaft, a repair far more expensive than the initial noise diagnosis.
• Clean accessible sensor connectors with electronic contact cleaner. (Every 30,000 miles) — Using compressed air or a dedicated electronics cleaner blows out dust and prevents moisture-induced corrosion that leads to high resistance and intermittent signals.

Frequently Asked Questions

What does 'Bank 2, Sensor B' mean?

Bank 2 is the side of the engine that does not contain cylinder #1. On a V6 or V8, this is typically the driver's side on a RWD vehicle. 'Sensor B' universally refers to the sensor monitoring the exhaust camshaft.

What are the most common mistakes when diagnosing P0390?

The most common mistake is immediately replacing the camshaft sensor without checking the oil level or inspecting for wiring damage. Technicians often miss oil leaks contaminating the connector, leading to the code returning. Using a cheap aftermarket sensor is another frequent error that guarantees repeat failure.

Why did the code come back after I replaced the sensor?

If the code returns, the sensor was not the root cause. The actual problem is damaged wiring, a stretched timing chain, low oil pressure, or a faulty VCT solenoid. It also happens if you installed a low-quality aftermarket replacement sensor.

Does the quality of the replacement sensor matter?

Yes, sensor quality matters significantly. Low-cost, non-OEM sensors have a high failure rate and incorrect electronic tolerances. Always use an OEM part to ensure reliability and prevent the code from returning immediately.

What is a camshaft sensor relearn procedure?

After replacing a camshaft sensor, some vehicles require the PCM to 'relearn' the new sensor's specific electronic characteristics. This requires a professional-grade scan tool to initiate the procedure. Failing to perform a relearn causes rough running or a no-start condition even with a perfect sensor.

Can I just clean the camshaft position sensor?

If the sensor is covered in oil from a leak, clean the oil from the connector and sensor body as part of the repair. However, cleaning does not fix a sensor that has failed internally. The fault is usually with the internal electronics, not surface contamination.

What is the difference between a Hall-effect and a magnetic reluctance sensor?

A Hall-effect sensor is an active sensor with three wires (power, ground, signal) that produces a clean, digital square wave (0V-5V). A magnetic reluctance sensor is a passive, two-wire sensor that generates its own AC voltage. Hall-effect sensors are more common on modern vehicles and require different testing methods.

Can a weak battery cause a P0390 code?

Yes, a weak or failing battery causes a voltage drop during engine cranking. This low voltage disrupts the signals from various sensors, including the camshaft position sensor, triggering a false code. Always test the battery if you experience starting issues alongside this code.

Will the P0390 code clear itself?

No, the code does not clear itself even if the fault is intermittent. You must repair the underlying problem and manually clear the code with an OBD-II scanner. The Check Engine Light remains on until the code is cleared.

What happens if I ignore the P0390 code?

Ignoring P0390 leads to persistent starting problems, poor engine performance, bad fuel economy, and dangerous stalling in traffic. Over time, the resulting misfires dump raw fuel into the exhaust, causing catastrophic damage to the catalytic converter. It also causes an automatic failure on state emissions tests.

Key Takeaways

• P0390 indicates the engine computer lost the signal from the Bank 2 exhaust camshaft sensor, causing hard starts, stalling, and up to a 20% drop in fuel economy.
• Always check the engine oil level and inspect the sensor's wiring harness for oil contamination or chafing before spending $40-$110 on a replacement sensor.
• If replacing the sensor, use an OEM part (like Motorcraft or Mopar); cheap aftermarket sensors have high failure rates and frequently cause the P0390 code to return immediately.
• Do not drive extensively with an active P0390 code, as the resulting misfires dump unburnt fuel into the exhaust and destroy a $1,500+ catalytic converter within months.
• On 2018-2020 Ford 5.0L engines, P0390 is often caused by a faulty VCT oil control solenoid (TSB 18-2360), while on Jeep 3.6L engines, it frequently points to a leaking oil cooler or failing rocker arms.