P0328: How to Diagnose & Fix — Knock Sensor 1 Circuit High Input (Bank 1)
3 vehicles · 2 makes · $80-$7,500 repair
How to diagnose and fix P0328: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Kia Sorento · 2011–2019
The Theta II 2.4L and 2.0T GDI engines in 2011-2019 Sorentos can experience catastrophic engine seizure due to machining debris left in the crankshaft oil passages during manufacturing. Metal shavings restrict oil flow to rod and main bearings, causing premature bearing wear and eventual engine lock-up. Over 340,000 Sorentos were included in NHTSA Recall 17V-224. Kia extended the powertrain warranty to 10 years/120,000 miles for affected vehicles and deployed the Knock Sensor Detection System (KSDS) software update to detect early bearing deterioration.
Common Symptoms
- Engine knocking or ticking noise that worsens over time
- Oil pressure warning light illuminated
- Metal shavings found in oil during changes
- Sudden engine stall while driving
- Excessive oil consumption (more than 1 qt per 1,000 miles)
- Check engine light with bearing-related codes
How to Fix
Check VIN eligibility for extended warranty (10 years/120,000 miles). Have dealer perform KSDS software update to detect early bearing failure. If engine is knocking, dealer will perform oil consumption test and bearing inspection. Complete engine replacement required if bearings are scored. Dealer replaces with updated long block assembly under warranty if eligible.
Owner tips & cautions
- WarningIf you hear any knocking, stop driving immediately. Continued operation with failing bearings causes catastrophic damage that may not be covered if engine locks up completely
- TipCheck your VIN at owners.kia.com/recalls - even if past the original warranty, the extended 10yr/120k warranty applies to Theta II bearing failures
- TipUse 0W-20 full synthetic oil and change every 5,000 miles to maximize bearing life. Pennzoil Platinum or Mobil 1 are frequently recommended on KiaForums
Sources for this issue (3)
Kia K5 · 2021–2025
The 2.5L Theta II engine in certain K5 models has experienced knock sensor faults and engine knock concerns. The knock sensor may trigger false positives or fail to detect actual detonation, causing the ECU to either retard timing unnecessarily (reducing power) or fail to protect against harmful knock. Kia issued a software update to improve knock detection logic, but some owners report persistent issues after the update.
Common Symptoms
- Check engine light with knock sensor codes
- Reduced engine power or sluggish acceleration
- Audible pinging or knocking under load
- Poor fuel economy from excessive timing retard
- Engine hesitation during acceleration
How to Fix
Visit a Kia dealer for the latest ECU software update (TSB SA508) that improves knock detection calibration — this is typically performed at no cost. If the knock sensor itself has failed, replacement costs $200-$400 including labor. Use only 87+ octane fuel as specified. If actual engine knock is present (metallic pinging under load), have the engine inspected immediately as the Theta II engine family has a known history of connecting rod bearing issues in earlier applications. Kia has extended warranty coverage on some Theta II engines.
Owner tips & cautions
- TipCheck if your VIN is covered under the Kia engine warranty extension. Many Theta II engines have extended coverage to 150,000 miles for knock-related failures.
- TipRequest the latest ECU calibration update at every service visit. Kia has released multiple updates to improve knock detection and engine protection logic.
Subaru Forester · 1998–2005
The single knock sensor bolted to the top of the EJ block on SF- and early SG-generation Foresters has a brittle plastic/resin housing that cracks after years of heat cycling directly on the block. Once cracked, the piezo element's circuit reads out of range and the ECU sets P0325. The car keeps running, but the ECU falls back to a conservative safe ignition map: owners report noticeably reduced power, sluggish throttle response and a measurable drop in fuel economy. The failure is common enough that many independent shops replace the sensor on any high-mileage EJ Forester showing that code without further diagnosis. A secondary cause is the sensor wiring harness chafing or the connector corroding, so the harness should be inspected before condemning the sensor.
Common Symptoms
- Check engine light with P0325
- Reduced power and sluggish acceleration
- Worse fuel economy
- Engine feels flat under load
- Code returns shortly after a replacement sensor is overtightened
How to Fix
Replace the knock sensor — it sits on top of the block under the intake manifold and is reachable with a 12mm socket and extensions, typically about 30-60 minutes of work. Torque matters: overtightening cracks the new sensor's housing and brings the code straight back, so use the specified low torque value and do not impact it on. Inspect the harness pigtail and connector for green corrosion or chafe damage at the same time, and clear the code and confirm the ECU returns to normal timing. Parts are inexpensive. No recall or warranty extension applies.
Sources for this issue (3)
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P0328 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0328 mean?
P0328 stands for "Knock Sensor 1 Circuit High Input (Bank 1)." This code means the knock sensor on engine bank 1 produced a voltage signal higher than its normal expected range. The knock sensor detects the vibrations of engine knock (detonation) so the computer can pull back ignition timing and protect the engine from damage. A high-input reading typically indicates an electrical issue such as a short to voltage or a wiring/connector fault, rather than genuine, sustained knock. While the sensor is faulted, the engine may default to conservative timing, slightly hurting performance and fuel economy.
What are the most common causes of P0328?
The most common causes of P0328 are: Faulty knock sensor (Bank 1, Sensor 1), Sensor wiring shorted to voltage or power, Damaged or corroded sensor connector, Loose or improperly torqued sensor mounting, Chafed/pinched wiring harness, Grounding or shielding fault in the circuit, Faulty engine control module (PCM) — rare. The specific cause varies by vehicle.
How much does it cost to fix P0328?
Repair costs for P0328 range from $80 to $7,500, depending on the vehicle and root cause.
Which vehicles are affected by P0328?
Au7o has documented P0328 across 3 vehicle models from 2 manufacturers: Kia, Subaru.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.