P0325 on 2013-2020 Lincoln MKZ 2.0L: Knock Sensor Circuit Malfunction Causes and Fixes

What's Unique About the 2013-2020 Lincoln MKZ

The Lincoln MKZ from 2013-2020 shares its platform and 2.0L engine with the Ford Fusion. This means that issues and repairs are often identical between the two models. 🎬 Watch: Location and replacement guide for MKZ and Fusion hybrids For this engine, the knock sensor is located on the engine block, underneath the intake manifold. While some vehicles require complete removal of the manifold for access, on the MKZ and its platform mates it is often possible, though difficult, to replace the sensor without removing the intake manifold, which can save significant labor time.

Symptoms You May Notice

• Check Engine Light is on
• Reduced engine power and sluggish acceleration
• Decreased fuel economy
• Audible engine pinging or knocking, especially under load (though this is a symptom of actual knock, not just the sensor fault)
• Hesitation during acceleration

Most Likely Causes

1. Faulty Knock Sensor 🔴 High Probability → Shop Ignition Knock (Detonation) Sensor Sensors are electronic components that can fail over time due to extreme heat cycles and constant vibration. Cracks can form in the sensor housing, allowing moisture to enter and damage the internal piezoelectric element.
   How to confirm: After verifying the wiring is intact, the sensor itself is the most likely culprit. It can be tested with a multimeter for proper resistance, though specifications can be hard to find. Replacement is often the most practical diagnostic step if the wiring is good. 🎬 Watch: How to test a knock sensor using a multimeter
   Typical fix: Replace the knock sensor.
   Est. part cost: $40-$100
2. Damaged Wiring or Connector 🟡 Medium Probability The wiring harness is located in a high-heat area of the engine bay, making it susceptible to brittleness, corrosion, or damage. Rodents are also known to chew on the wiring in the valley under the intake manifold, causing an open or short circuit. A TSB for a different Ford EcoBoost engine (3.5L) also points to wire chafing as a cause for this code.
   How to confirm: Visually inspect the wiring harness leading to the knock sensor for any signs of breaks, chafing, melting, or corrosion at the connector. Use a multimeter to check for continuity between the PCM and the sensor connector, and verify there is no short to ground or power.
   Typical fix: Repair the damaged section of the wiring harness or replace the connector pigtail.
   Est. part cost: $15-$50

Rare But Worth Checking

• Powertrain Control Module (PCM) Fault: → Shop Engine Control Module (ECM) This is very rare. The PCM should only be considered after all other possibilities, including the sensor and wiring, have been exhaustively tested and ruled out. A Reddit user with multiple sensor codes was advised to investigate the PCM, but this is an outlier case.
• Loose Sensor Mounting: The knock sensor is a microphone that must be torqued correctly to the engine block to detect vibrations properly. If the bolt is loose, it can't 'hear' the engine correctly, which may trigger a circuit code. Ensure the mounting surface is clean and the sensor is torqued to specification, which is typically around 18 lb-ft (25 N.m) for similar engines.

Diagnosis Steps

1. Retrieve the stored trouble code(s) with an OBD-II scanner to confirm P0325 is present.
2. Visually inspect the knock sensor wiring harness and connector. The sensor is located on the front of the engine block, under the intake manifold. Look for any obvious signs of damage, melting, rodent chew marks, or corrosion.
3. If the wiring looks good, disconnect the sensor and check the connector terminals for a clean, tight fit.
4. Using a digital multimeter, check for the correct reference voltage and ground at the connector (refer to a service manual for specific values for your vehicle).
5. Test the continuity of the wiring between the PCM connector and the knock sensor connector to rule out an open or short in the harness.
6. If the wiring and connector are confirmed to be good, the knock sensor itself is the most likely cause of the fault.
7. Replace the knock sensor. It is critical to clean the mounting surface on the engine block thoroughly before installation to ensure proper contact. Torque the new sensor's retaining bolt to the manufacturer's specification (approx. 18 lb-ft or 25 N.m). Do not overtighten.
8. Clear the trouble code and perform a test drive, putting the engine under various loads to ensure the fault does not return.

Parts You'll Likely Need

• Knock Sensor (OEM #Motorcraft KS-31 (Ford P/N: 7T4Z-12A699-A)) — This is the most common component to fail in the knock sensor circuit, triggering the P0325 code.
  Trusted brands: Motorcraft, Bosch, NTK, Duralast
  OEM price range: $60-$90
  Aftermarket price range: $30-$70

Technical Service Bulletins (TSBs) & Recalls

• While no TSB exists specifically for P0325 on the 2.0L MKZ, Ford TSB 18-2367 was issued for the 3.5L EcoBoost engine for the same code (P0325/P0327). The cause was identified as a wire chafing condition near a connector. This reinforces the importance of thoroughly inspecting the wiring harness for damage as a primary diagnostic step.

Platform-Specific Known Issues

• Rodent Damage: The location of the wiring harness under the intake manifold makes it an attractive place for rodents to build nests, and they often chew through the knock sensor wires. This is a common finding when diagnosing P0325 on Ford/Lincoln vehicles.

Mechanic-Grade Diagnostic Values

• Knock Sensor (KS) circuit voltage to Signal Return (SIG RTN) circuit — expected: 1.0 - 4.0 Volts. Failure: Voltage is less than 1.0V or greater than 4.0V, indicating an open or short in the harness or a faulty PCM.
• Knock Sensor input voltage at PCM (General OBD-II logic) — expected: Between 0.2V and 4.8V with engine speed > 2000 RPM. Failure: Voltage is above 4.8V (short to power) or below 0.2V (short to ground/open circuit).
• Knock Sensor AC Voltage Generation — expected: A small AC voltage is generated on a multimeter set to millivolts when the engine block is tapped near the sensor.. Failure: No voltage is generated, indicating a dead sensor.

Wiring & Ground Locations

• G101 — Left front of the engine compartment.. A poor engine ground can introduce electrical noise or cause voltage drops, potentially affecting sensor readings and triggering circuit fault codes.
• G106 — Right front of the engine compartment.. Serves as a primary ground point for various engine components. Corrosion or looseness here can lead to intermittent and hard-to-diagnose electrical faults.
• G109 — Rear of the engine block.. Being located directly on the engine, this ground is critical for sensors mounted to the block. A faulty ground here could directly impact the knock sensor circuit's integrity.
• G110 — Right front of the engine on 2.0L models.. Ensures a solid ground path for the engine assembly to the chassis, which is essential for all engine electronics, including the knock sensor circuit.

OEM Part Supersession History

• 7T4Z-12A699-AB → 7T4Z-12A699-A — Part revision or manufacturer change.
• 7T4Z-12A699-AA → 7T4Z-12A699-A — Part revision or manufacturer change.

Model Year Variations Within This Range

• 2017-2020: The Lincoln MKZ received a major facelift for the 2017 model year, including a new grille and the introduction of an optional 3.0L V6. However, for vehicles equipped with the 2.0L EcoBoost or 2.0L Hybrid engines, the knock sensor part, location, and diagnostic procedure for P0325 remained unchanged from the 2013-2016 models.

Diagnostic Flowchart

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used wiring harness connector pigtail is a reasonable choice if the original is damaged by heat or rodents. It is a simple component that can be visually inspected for integrity.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a wiring pigtail, ensure the plastic is not brittle and the locking tab is intact.
• Check connector pins for any signs of green or white corrosion.
• For a sensor, inspect the plastic housing for any cracks and ensure the metal mounting surface is flat and undamaged.

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

• Powertrain Control Module (PCM)

Aftermarket brands forum-validated for this vehicle:

• NTK
• Bosch
• Motorcraft (OEM)

Real Owner Stories

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

Related OBD-II Codes

• P0327 — Knock Sensor 1 Circuit Low Input. This code is often triggered by the same faults as P0325, such as a shorted wire or a failed sensor. A Ford TSB for a related engine lists both P0325 and P0327 for the same wire chafing issue.
• P0330 — Knock Sensor 2 Circuit Malfunction (Bank 2). While the 2.0L I4 engine only has one bank and will not set this code, it is the direct equivalent for P0325 on V-engines in the same Ford/Lincoln family, caused by the same types of failures.
• P0332 — Knock Sensor 2 Circuit Low Input (Bank 2). Similar to P0330, this is the Bank 2 equivalent of P0327 and is relevant to owners familiar with other EcoBoost engines, as seen in forum discussions.
• MULTIPLE SENSOR CODES (E.G., P0107, P0340, P0121) — If P0325 appears with a large number of other unrelated sensor circuit codes, it may not be an isolated sensor failure. As seen in one owner report, this can point to a more significant issue like widespread rodent damage to the main harness or a failing Powertrain Control Module (PCM).

Frequently Asked Questions