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P0325 on 2016-2017 Ford Explorer 3.5L EcoBoost: Knock Sensor Circuit Malfunction Causes and Fixes

This code indicates a fault in the Bank 1 knock sensor circuit. On the 3.5L EcoBoost, the most common cause is a chafed wiring harness near the back of the engine, as noted in a Ford TSB. If the sensor itself has failed, it's a labor-intensive job requiring removal of the intake manifold, so professional repair is recommended.

19 minutes to read 2016-2017 Ford Explorer
Most Likely Cause
Chafed Wiring Harness
Difficulty
5/5
Est. Time
3.9 hrs
DIY Doable?
🔧 Shop
Shop Labor
$300 – $1200
Parts Price
$10 – $300
⚠️ Drivable, but... — You can drive, but the PCM may put the engine in a reduced power or "limp mode" to prevent damage. With a compromised knock detection system, the PCM defaults to a conservative timing map. Ignoring a potential knocking condition can lead to serious internal engine damage over time.
Key Takeaways
  • For a 2016-2017 Explorer with the 3.5L EcoBoost, P0325 is very often caused by a chafed wire near the back of the engine, as outlined in Ford TSB 18-2367.
  • Always inspect the wiring harness at connector C109 before assuming the sensor itself has failed.
  • If the sensor must be replaced, it is a difficult, labor-intensive job that requires removing the intake manifold.
  • Due to the high labor cost, it is strongly recommended to replace both knock sensors and their connecting harness at the same time if you have to remove the intake.
  • Driving with this code can cause reduced performance and may lead to engine damage if the underlying knock condition is severe and persistent.
The diagnostic trouble code (DTC) P0325 stands for "Knock Sensor 1 Circuit Malfunction (Bank 1)". The knock sensor acts like a small microphone bolted to the engine, listening for vibrations from engine knock (also called detonation or pinging). This code means the Powertrain Control Module (PCM) has detected an electrical problem in the circuit for the knock sensor on Bank 1. Bank 1 is the cylinder bank closer to the firewall on this transverse-mounted engine. The PCM uses the sensor's signal to precisely adjust ignition timing to prevent engine damage that can be caused by knocking. A P0325 code indicates the PCM is not receiving a valid signal, which could be due to an open wire, a short, or an out-of-range voltage; it does not automatically mean the engine is knocking.

What's Unique About the 2016-2017 Ford Explorer

For the 2016-2017 Explorer with the 3.5L EcoBoost, this code is frequently caused by a specific wiring issue. Ford issued Technical Service Bulletin (TSB) 18-2367 for vehicles built on or before September 30, 2016, which points to a wire chafing condition near the knock sensor connector C109 at the back of the engine. If the sensor itself needs replacement, the job is significantly more complex than on many other engines because both knock sensors are located in the valley of the engine, underneath the entire intake manifold, requiring partial draining of the cooling system and removal of the intake to access them.

Professional service recommended: Accessing the knock sensors requires removing the intake manifold, which is a labor-intensive procedure not recommended for beginners. The TSB repair for a chafed wire also requires working in a tight space at the rear of the engine and may involve draining coolant to move components for better access.

Symptoms You May Notice

  • Check Engine Light illuminated
  • Reduced engine power and poor acceleration
  • Engine may feel sluggish
  • Audible metallic pinging or knocking sound from the engine, especially during acceleration
  • Decreased fuel economy
  • Hesitation during auto start-stop events
⚠️ Don't Waste Money on the Wrong Fix
  • Replacing the knock sensor without checking for the TSB-related wiring issue first. The chafed wire is a very common cause and inspecting it first can save significant time and money.

Most Likely Causes

  1. Chafed Wiring Harness 🔴 High Probability Ford TSB 18-2367 specifically identifies a wire chafing issue near connector C109 on vehicles built on or before September 30, 2016. The harness can rub against the cylinder head or other components at the rear of the engine bay.
    How to confirm: Visually inspect the wiring harness at the back of the engine near the firewall for signs of rubbing or exposed wires. This is connector C109. Access may require removing the air cleaner outlet pipe.
    Typical fix: Repair the damaged section of the wire using a splice kit (Ford specifies part 3U2Z-14A088-AB) and protect the harness with 3/8 inch convoluted tubing and electrical tape to prevent future chafing.
    Est. part cost: $10-$30 for a wire splice kit and loom.
  2. Faulty Knock Sensor (Bank 1) 🟡 Medium Probability The sensors are located in the hot engine valley, which can lead to failure over time. They are sensitive piezoelectric microphones that can degrade.
    How to confirm: After confirming the wiring is intact, the sensor itself must be tested. This requires removing the intake manifold for access. The sensor's resistance can be checked, though replacement is common given the labor to access it.
    Typical fix: Replace the knock sensor. It is highly recommended to replace both knock sensors (Bank 1 and Bank 2) and the small connecting harness at the same time due to the high labor cost to access them.
    Est. part cost: $60-$90 for one OEM sensor, plus intake gaskets.
  3. Loose or Corroded Connector ⚪ Low Probability
    How to confirm: Check the connection at the main harness connector (C109) and at the sensor itself (under the intake) for looseness, corrosion, or pushed-out pins.
    Typical fix: Clean the connector terminals with electrical contact cleaner and apply dielectric grease. Ensure it is securely reconnected.
    Est. part cost: $5-$10 for electrical contact cleaner and grease.

Rare But Worth Checking

  • Powertrain Control Module (PCM) Failure: This is very uncommon. The PCM should only be considered after all other possibilities, including wiring and the sensor itself, have been exhaustively ruled out.
  • Internal Engine Problems: Severe mechanical issues that cause excessive engine noise or vibration can sometimes be misinterpreted by the PCM as a sensor circuit fault, though this is rare.

Diagnosis Steps

  1. Check the vehicle's build date to see if it falls on or before September 30, 2016, making TSB 18-2367 applicable.
  2. Scan the PCM for any other stored trouble codes. Address other codes first if they are present.
  3. Carefully inspect the knock sensor wiring harness near connector C109 at the rear of the engine for any signs of chafing, melting, or damage, as detailed in TSB 18-2367. This may require removing the air cleaner assembly for access.
  4. If wiring damage is found, repair the wire(s) and protect the harness. The TSB procedure notes this is a 1.7-hour job and may require partially draining coolant to move a coolant outlet for access.
  5. Clear the codes and test drive to see if P0325 returns.
  6. If the wiring is intact, the next step is to test the knock sensor itself. This requires draining the coolant and removing the upper intake manifold to access the sensors in the engine valley.
  7. Once the intake is removed, inspect the sub-harness connecting the two knock sensors for damage or brittleness from heat.
  8. Test the resistance of the knock sensor. If it is out of specification, it needs to be replaced. However, given the labor involved, it is standard practice to replace both sensors and the harness regardless.
  9. When replacing a sensor, ensure the mounting surface on the engine block is clean and torque the new sensor to specification (e.g., 10 Nm or 89 lb-in). Improper torque can affect sensor performance.

Parts You'll Likely Need

  • Knock Sensor (OEM #Motorcraft KS-31 (Ford BL3Z-12A699-A)) — This is the sensor that fails. It's located under the intake manifold. It's recommended to replace both at once.
    Trusted brands: Motorcraft, Delphi, Standard Motor Products
    OEM price range: $60-$90
    Aftermarket price range: $30-$60
  • Upper and Lower Intake Manifold Gaskets (OEM #Motorcraft AA5Z-9439-BA (Lower), HL3Z-9439-C (Upper, set of 3 small oval gaskets)) — These must be replaced anytime the intake manifold is removed to access the knock sensors.
    Trusted brands: Motorcraft, Fel-Pro
    OEM price range: $60-$100 for a complete set
    Aftermarket price range: $30-$60
  • Wire Splice Repair Kit (OEM #3U2Z-14A088-AB) — This is the Ford-specified part for repairing the chafed harness described in TSB 18-2367.
    Trusted brands: Motorcraft
    OEM price range: $20-$30
    Aftermarket price range: $10-$15

Related Codes That Often Appear With This One

  • P0330 — This is the code for the Bank 2 knock sensor circuit. TSB 18-2367 notes that these codes can appear together due to the same wiring harness issue. If one sensor fails, it's common for the other to fail around the same time.
  • P0327 — This code indicates low input from the knock sensor circuit (Bank 1). It can also be triggered by the same wiring chafe issue described in TSB 18-2367.
  • P0332 — This is the code for Knock Sensor 2 Circuit Low Input (Bank 2). TSB 18-2367 lists this as another possible code caused by the same chafing wire.

Technical Service Bulletins (TSBs) & Recalls

  • TSB 18-2367: Addresses an illuminated MIL with knock sensor DTCs (including P0325) due to a wire chafing condition on 2016-2017 Explorer/Police Interceptor Utility with the 3.5L EcoBoost engine.

Platform-Specific Known Issues

  • TSB 18-2367: Chafed Wiring Harness: For vehicles built on or before 30-Sep-2016, a chafed wire condition near the knock sensor connector C109 is a known issue that can cause codes P0325, P0327, P0330, and/or P0332. The repair is a 1.7-hour warranty job.

Mechanic-Grade Diagnostic Values

  • Knock Sensor Input Voltage (PCM check) — expected: Between 0.2 volts and 4.8 volts with engine speed above 2000 RPM.. Failure: A voltage reading less than 0.2V or greater than 4.8V will trigger the code.
  • Knock Sensor AC Voltage Output (Dynamic Test) — expected: A fluctuating AC voltage reading on a multimeter when the engine block near the sensor is lightly tapped.. Failure: No voltage reading or a reading of less than 10 millivolts during the tap test suggests a faulty sensor.
  • Knock Sensor Bolt Torque — expected: 10 Nm (89 lb-in). Failure: Incorrect torque can cause the sensor to malfunction, either by not detecting knock or by being overly sensitive.

Wiring & Ground Locations

  • C109 — At the rear of the engine, near the firewall. The TSB identifies this as the location of the potential wire chafe against the cylinder head.. This is the main connector for the knock sensor harness. Damage here is the most common cause of P0325 and related codes on vehicles built on or before Sept 30, 2016.
  • Engine Ground Stud (GD200) — On the back side of the left (firewall side) cylinder head.. A poor ground connection can introduce electrical noise or cause incorrect voltage readings for various sensors, including the knock sensor circuit.
  • Knock Sensor 1 (Bank 1) PCM Pin — Pin 3 at connector C1551E on the Powertrain Control Module (PCM). The wire color is typically Brown/Blue (BRN/BLU).. This is the specific pin at the PCM where the signal from the Bank 1 knock sensor arrives. It is used for continuity and voltage testing from the PCM side of the circuit.

Real Owner Repair Stories

  • YouTube channel 'Ford Boss Me' (2016 Ford Explorer 3.5L EcoBoost) — Check Engine Light with codes P0327 and P0332 (Knock Sensor Circuit Low for Bank 1 and Bank 2).
    ✅ What actually fixed it The technician identified a chafed wiring harness rubbing on the cylinder head near connector C109, exactly as described in TSB 18-2367. A temporary fix involved wrapping the chafed area with electrical tape to insulate the wires, which cleared the codes. The permanent recommended fix is to splice the damaged wires using the specified Ford repair kit and protect the harness with convoluted tubing.
  • NHTSA ODI #10712827 — An owner of a related Ford model reported that the check engine light remained on with P0325 present alongside throttle body codes P2104, P2100, and P2112.

OEM Part Supersession History

  • AL3Z-12A699-BA → AL3Z-12A699-A / Motorcraft KS-31 — Standard part number revision/update.
    Heads up: The part listed in Pass 2, BL3Z-12A699-A, appears to be for a different application. The correct supersession for this vehicle appears to be AL3Z-12A699-BA to AL3Z-12A699-A.

Model Year Variations Within This Range

  • 2016: The 2016 model year uses the first-generation 3.5L EcoBoost engine. These engines had updates in 2013, including larger turbos and a Bosch direct injection system.
  • 2017: The 2017 model year marked the introduction of the second-generation 3.5L EcoBoost, which was a significant redesign. It featured a dual-injection system (both port and direct injection), a dual-chain cam drive, and was paired with a new 10-speed automatic transmission. While the knock sensor location and function remain similar, other engine components and management systems are different.
  • Vehicles built on or before 30-Sep-2016: These vehicles are specifically called out in TSB 18-2367 as being prone to the wire chafing issue at connector C109, which causes P0325 and related codes.

Diagnostic Flowchart

Start by checking the vehicle build date and scanning for concurrent codes. This diagnostic focuses on the common wiring harness chafing issue identified in TSB 18-2367 before moving to internal sensor replacement.
Check the door jamb sticker. Was the vehicle built on or before September 30, 2016?
Inspect the wiring harness near connector C109 at the rear of the engine (near the firewall). Is there evidence of chafing or exposed copper?
→ Perform TSB 18-2367 repair: Use splice kit 3U2Z-14A088-AB to repair the wire. Protect the harness with 3/8 inch convoluted tubing and electrical tape to prevent future contact with the cylinder head.
Disconnect C109 and inspect the pins. Is there corrosion, moisture, or pushed-out terminals?
→ Clean terminals with electrical contact cleaner, apply dielectric grease, and ensure the connector clicks firmly into place. Clear codes and test drive.
The fault is likely internal. Are you prepared to remove the upper intake manifold to access the engine valley?
With the intake manifold removed, test the Bank 1 knock sensor resistance. Is it out of spec?
→ Replace both Bank 1 and Bank 2 knock sensors and the valley sub-harness. Clean the mounting surfaces and torque sensors to 10 Nm (89 lb-in). Replace intake manifold gaskets before reassembly.
→ If you hear audible metallic pinging or 'rattle' on cold start, you may have timing chain stretch (TSB 18-2305). This mechanical noise can 'ghost' a P0325 code. Verify engine timing before replacing sensors.
Remove the air cleaner outlet pipe and inspect the knock sensor sub-harness for heat damage or rodent chewing. Is the harness intact?
→ Repair or replace the knock sensor sub-harness. Ensure the harness is routed away from the turbocharger heat shields to prevent melting.
Disconnect C109 and inspect the pins. Is there corrosion, moisture, or pushed-out terminals?
→ Clean terminals with electrical contact cleaner, apply dielectric grease, and ensure the connector clicks firmly into place. Clear codes and test drive.
The fault is likely internal. Are you prepared to remove the upper intake manifold to access the engine valley?
With the intake manifold removed, test the Bank 1 knock sensor resistance. Is it out of spec?
→ Replace both Bank 1 and Bank 2 knock sensors and the valley sub-harness. Clean the mounting surfaces and torque sensors to 10 Nm (89 lb-in). Replace intake manifold gaskets before reassembly.
→ If you hear audible metallic pinging or 'rattle' on cold start, you may have timing chain stretch (TSB 18-2305). This mechanical noise can 'ghost' a P0325 code. Verify engine timing before replacing sensors.
→ Resolve misfires first. On the 3.5L EcoBoost, carbon buildup on intake valves or worn spark plugs can cause vibrations that trigger knock sensor codes. Perform an induction cleaning or replace plugs before diagnosing the sensor circuit.

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

  • Timing Chain Stretch & Cam Phaser Rattle on Cold Start 🔴 High — Common on first-generation 3.5L EcoBoost engines. A rattle for 2-5 seconds on a cold start is the primary symptom. (Ref: TSB 18-2305 (for F-150, but describes the same issue), TSB 23-2143 (updates for 2017+ models))
  • Internal Water Pump Failure 🔴 High — The water pump is driven by the timing chain. When it fails, it can leak coolant into the crankcase, leading to catastrophic engine failure if not caught early. Often occurs post-100k miles.
  • Carbon Buildup on Intake Valves 🟠 Medium — As a direct-injection-only engine (Gen 1), oil vapor can bake onto the intake valves over time, causing rough idle and hesitation. More common on vehicles used for short trips.
  • Cracked Exhaust Manifolds 🟠 Medium — Can lead to ticking noises and exhaust leaks. The high heat from the turbochargers can cause the manifolds to crack over time.
  • Surge or Hesitation Under Light Load 🟡 Low — Some vehicles may exhibit a surge or hesitation around 50-60 MPH in 6th gear. (Ref: TSB SSM 47500)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: Using a used part is generally not recommended for this repair. The knock sensors themselves are wear items located in a high-heat area, and the labor to access them is extremely high. A used wiring harness pigtail could be a viable option if repairing a damaged connector, provided it is in excellent condition with no brittleness.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

  • For a harness pigtail, inspect for any signs of cracking, brittleness, or heat damage.
  • Ensure connector locking tabs are intact and not broken.
  • Verify there is no corrosion on the pins.

OEM-only on this vehicle (don't cheap out):

  • Knock Sensor: Due to the high labor cost of replacement, using an OEM (Motorcraft) or a top-tier OEM-supplier brand is critical. Cheaper aftermarket sensors have a higher failure rate and may not have the correct piezoelectric frequency response, leading to a repeat repair.
  • Intake Manifold Gaskets: Always use new, high-quality gaskets (OEM/Motorcraft or Fel-Pro) to prevent vacuum leaks after reassembly.

Aftermarket brands forum-validated for this vehicle:

  • NTK (sensor division of NGK)
  • Delphi
  • Standard Motor Products (SMP)

Brands owners have reported issues with on this vehicle:

  • Unbranded or 'white-box' sensors from online marketplaces are frequently cited in forums as being dead-on-arrival or failing shortly after installation.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

2017 Ford F-150 3.5L EcoBoost

Symptoms: Owner was quoted for a knock sensor repair requiring intake manifold removal and cooling system drainage.

What fixed it: Knock sensor replacement (requires removing intake manifold and draining coolant).

Cost: $1200-$1200

Source hint: Ford F150 Forum - Knock sensor replacement

2018 Ford F-150 3.5L EcoBoost

Symptoms: Code P0330; sensors located under the fuel injection rails making it a complex job.

What fixed it: Repair performed under warranty due to complexity and location of sensors.

Source hint: Ford F150 Forum - Knock sensor location for GEN2 3.5L EB, and P0330 code

2016-2017 Ford Explorer 3.5L EcoBoost

Symptoms: Illuminated MIL with knock sensor DTCs due to wire chafing near connector C109.

What fixed it: Repairing the damaged wire using splice kit 3U2Z-14A088-AB and adding 3/8 inch convoluted tubing.

Source hint: TSB 18-2367: Addresses an illuminated MIL with knock sensor DTCs (including P0325)

  • P0327 — Identified in TSB 18-2367 as a companion code that can be triggered by the same chafed wiring harness condition at connector C109.
  • P0330 — The Bank 2 equivalent of P0325; often appears alongside it due to shared wiring harness issues or failures in the engine valley sub-harness.
  • P0332 — Another knock sensor circuit code listed in TSB 18-2367 resulting from the same harness rubbing issue on 2016-2017 3.5L EcoBoost models.

Frequently Asked Questions

Does TSB 18-2367 apply to my 2017 Ford Explorer 3.5L EcoBoost?
TSB 18-2367 applies to 2016-2017 Explorers with the 3.5L EcoBoost engine built on or before September 30, 2016. It addresses wire chafing near connector C109 that causes knock sensor codes like P0325.
Where is the common wiring failure point for P0325 on this vehicle?
The failure typically occurs at the rear of the engine bay near the firewall at connector C109. The harness can rub against the cylinder head or other components, leading to exposed wires.
What specific part is recommended for the wiring repair mentioned in the TSB?
Ford specifies using a wire splice kit, part number 3U2Z-14A088-AB, and protecting the repaired section with 3/8 inch convoluted tubing and electrical tape.
Why is the labor cost so high to replace the knock sensors on the 3.5L EcoBoost?
The knock sensors are located in the engine valley. Replacing them requires draining the coolant and removing the upper intake manifold, a process that can take several hours and may involve moving coolant outlets for access.
Should I replace both knock sensors if only Bank 1 (P0325) is failing?
Yes. Because of the high labor cost and the need to remove the intake manifold, it is standard practice to replace both knock sensors and the connecting sub-harness at the same time.
What is the correct torque specification for a new knock sensor on this engine?
New sensors should be torqued to 10 Nm (89 lb-in) on a clean mounting surface to ensure proper performance.
How to Replace Knock Sensors 2011-2019 Ford Explorer
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How to Replace Knock Sensors 2011-2019 Ford Explorer
ENGINE LIGHT CODE P0325 KNOCK SENSOR FORD C-MAX FORD FUSION LINCOLN MKZ
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ENGINE LIGHT CODE P0325 KNOCK SENSOR FORD C-MAX FORD FUSION LINCOLN MKZ
P0325 Code: Knock Sensor Malfunction (Bank 1) – Causes & Diagnosis
▶
P0325 Code: Knock Sensor Malfunction (Bank 1) – Causes & Diagnosis
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.

Year Coverage
This article covers the OBD-II Code P0325 (Deep Dive) for:
  • Ford Explorer: 20162017
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