What Are the Two Sensors on F-150 Valve Covers? (2015 3.5L Fix)

Ford F-150 What Are These Two Sensors On The Valve Covers Of 2015 3.5L: Diagnosis & Fix (2026)

If you are a 2015 Ford F-150 owner with the 3.5L EcoBoost engine, you have likely popped the hood and asked yourself: “Ford F-150 what are these two sensors on the valve covers of 2015 3.5l?” You are not alone. These mysterious components are often the source of engine shudder, rough idle, and check engine lights that dealerships charge hundreds to diagnose. In this 2026 guide, we will strip away the jargon and give you the exact diagnosis and repair steps to fix these sensors yourself, saving you a trip to the service bay.

The two sensors sitting atop your valve covers are the Variable Cam Timing (VCT) Solenoids (also known as cam phaser solenoids or oil control valves). They are critical for managing oil flow to the cam phasers, which adjust valve timing for power and efficiency. When they fail, your 3.5L EcoBoost starts acting like a completely different truck.

Diagnosis (Symptoms)

Before you start throwing parts at the problem, you need to confirm that these sensors are the culprit. The following symptoms are classic indicators of failing VCT solenoids on the 2015 Ford F-150 3.5L:

• Rough Idle & Engine Shudder: The truck feels like it is shaking or vibrating at a stoplight. This is often the first sign.
• Check Engine Light (CEL): Codes P0012 (Camshaft Position Timing Over-Retarded) or P0016 (Crankshaft/Camshaft Position Correlation) are common.
• Loss of Low-End Power: The truck feels sluggish off the line, struggling to accelerate from a stop.
• Poor Fuel Economy: A sudden drop in MPG, often by 2-4 miles per gallon.
• Engine Hesitation or Stalling: The engine may stumble when you press the gas, or even stall completely at low speeds.
• Hard Starting: The engine cranks longer than usual before firing up.

Important Note: These symptoms can also mimic cam phaser rattle or a failed timing chain tensioner. However, if you are asking “Ford F-150 what are these two sensors on the valve covers of 2015 3.5l?”, you are likely dealing with a solenoid issue, not a full phaser failure (yet).

Potential Causes

• Clogged Oil Passages: The VCT solenoids rely on clean engine oil. Sludge or debris can block the internal screens, preventing the solenoid from adjusting timing.
• Worn Internal Solenoid Mechanism: Over time, the electromagnetic coil or plunger inside the sensor wears out, causing intermittent or complete failure.
• Damaged Wiring or Connector: The electrical connector on top of the valve cover can corrode, break, or become loose, sending incorrect signals to the PCM.
• Low Oil Level or Pressure: These sensors are hydraulic. If your oil level is low or the oil pump is failing, the solenoids cannot function correctly.
• Contaminated Oil (Fuel Dilution): The 3.5L EcoBoost is prone to fuel dilution in the oil, which thins the oil and reduces the solenoid’s ability to hold pressure.
• Faulty PCM Programming: Rare, but a software glitch in the Powertrain Control Module can misinterpret sensor data, causing false failures.

Step-by-Step Fix (Technical but Clear)

This repair is considered intermediate. You will need basic hand tools and a torque wrench. Always disconnect the negative battery terminal before starting electrical work.

Tools & Parts Needed

• New VCT Solenoids (Bank 1 & Bank 2 – buy OEM or high-quality aftermarket like Dorman or Motorcraft)
• 8mm socket and ratchet
• Torx T25 bit (for valve cover bolts, if you need to move the harness)
• Dielectric grease
• Clean lint-free rag
• Engine oil (5W-30 for the 3.5L)
• Torque wrench (in-lb range)

Procedure

Step 1: Locate the Sensors
Open the hood. Look at the top of the engine. You will see two plastic valve covers. On the front of each valve cover (near the radiator) are two small, rectangular black sensors with a single wiring harness plugged into each. These are the VCT solenoids.

Step 2: Disconnect the Electrical Connectors
Press the tab on each connector and pull straight up. They can be stubborn. Use a small flathead screwdriver to gently pry if needed. Be careful not to break the plastic locking tab.

Step 3: Remove the Solenoids
Using an 8mm socket, remove the single retaining bolt holding each solenoid in place. The bolt is usually located on the side of the sensor. Once the bolt is out, grasp the solenoid firmly and pull straight up. It may require a slight twisting motion to break the seal. Note: Some oil will drip out. Have a rag ready.

Step 4: Inspect the Old Solenoids
Look at the bottom of the solenoid. You should see a metal screen filter. If it is clogged with black sludge, this is your problem. Also check the O-ring for damage.

Step 5: Install the New Solenoids
Apply a thin coat of clean engine oil to the new O-rings. This prevents them from tearing during installation. Insert the new solenoid straight into the bore. Push firmly until it seats fully. Install the retaining bolt and tighten to 89 in-lbs (10 Nm). Do not overtighten; you can crack the valve cover.

Step 6: Reconnect Electrical Connectors
Apply a small amount of dielectric grease to the inside of the connector pins to prevent future corrosion. Click the connector back on until you hear a positive snap.

Step 7: Clear Codes and Test
Reconnect the battery. Start the engine. The rough idle should vanish immediately. Use an OBD2 scanner to clear any stored codes (P0012, P0016, etc.). Take the truck for a test drive. The hesitation and shudder should be gone.

Pro Tip: If the problem returns within a few weeks, you likely have a deeper oil sludge issue. Consider an engine oil flush or switching to a high-quality full synthetic oil with a cleaning additive.

Cost Estimates (Parts vs Labor)

This is where the dealership vs. DIY math becomes crystal clear.

Dealership / Mechanic Shop

• Diagnostic Fee: $150 – $200 (just to tell you what you already suspect)
• Parts (OEM Ford): $120 – $180 per solenoid (x2 = $240 – $360)
• Labor: 1.5 – 2 hours at $150/hour = $225 – $300
• Total Dealer Cost: $615 – $860

DIY Repair

• Parts (High-Quality Aftermarket): $40 – $60 per solenoid (x2 = $80 – $120)
• Tools (if you don’t have them): $15 for a basic 8mm socket set
• Total DIY Cost: $95 – $135

Savings: You are looking at a minimum of $480 saved by doing this yourself. And you will have learned exactly what those two sensors are and how to fix them for life.

The Dealership Warning

Whether you are dealing with a turbo coolant leak, engine shudder, or failing cam phasers, dealership repair quotes can be devastating. Stop paying $200 diagnostic fees for known defects. Scroll up to use our F-150 Smart Mechanic’s Calculator to see your real options, or grab the Dealership Survival Guide to force Ford to cover the bill.

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