Owners of 2021 Kia Souls report catastrophic engine failures tied to defective piston oil rings in the 2.0L Nu MPI engine, often with no warning—no check engine light, no low-oil indicator, no alert whatsoever—until the vehicle stalls without restart or loses power on the highway. The failures cluster around excessive oil consumption (consuming a quart every 1,000–3,000 miles or requiring refills every few days), rough running, engine knocking and grinding at startup, erratic RPM fluctuations at idle, and sudden shutdowns while stopped at traffic lights or moving in traffic. Some vehicles exhibit oil-soaked spark plugs, abnormal exhaust smell, low compression in individual cylinders (102–130 PSI vs. normal 160+), and visible cylinder wall scoring.
Owners describe the recall remedy as inconsistent and ineffective. Many dealers installed only the Piston-Ring Noise Sensing System (PNSS) software without engine replacement, yet failures recurred after recall "completion." Some dealers falsely blame clogged air filters, customer maintenance records, or even theft damage, refusing to perform recall diagnostic tests (PNSS, oil consumption, compression, borescope). Others mark recalls complete based on a "tablet test pass" despite active stalling, knock codes (P0014/P0017, P1327, P0420, P0004), or owner-reported symptoms. Compression tests showing failure (102 PSI) are dismissed as unrelated to the recall. Parts shortages and month-long repair delays are common. Dealerships demand owner maintenance records as a precondition, or charge diagnostic fees ($99–$315) that should be covered. Owners report Kia corporate refusing to honor the recall, directing them to unavailable dealers, or claiming no remedy exists. In multiple cases, engines that failed during or immediately after recall service were determined to be caused by the recall repair itself—yet denied coverage.
Failure modes owners describe
Defective piston oil rings – excessive oil consumption without warning
Piston oil rings manufactured with defects in the 2.0L Nu MPI engine cause internal engine damage, cylinder bore scuffing, and oil loss into the combustion chamber. Owners report consuming 1–4+ quarts between scheduled oil changes or every few days, with no low-oil pressure warning light illuminated until catastrophic failure occurs.
When: Typically becomes apparent between 20,000–85,000 miles; can progress silently for months before engine seizure.
Symptoms owners cite: Excessive oil consumption requiring frequent top-offs; No low-oil warning light or check engine light before failure; Low or empty oil dipstick despite recent fill-ups; Engine running rough and making knocking or grinding noise; Rough idle with erratic RPM fluctuations; Oil deposits on spark plugs indicating oil in combustion chamber
Codes mentioned: P0014 (Camshaft Position Timing Over-Advanced Bank A), P0017 (Camshaft Position Timing Misalignment Bank A/B), P1327 (Piston Ring Noise Sensing System fault), P0420 (Catalyst System Efficiency Below Threshold), P0004 (Fuel Volume Regulator Control), Low compression (102–130 PSI vs. normal 160+ PSI) confirmed by dealer compression test
Repairs/costs cited: Recall SC336 (Campaign 21V-301 / 25V099) mandates engine replacement with Long Block Assembly (Part # 21101-QQK) or short block with all contaminated components replaced, plus installation of PNSS software. Owners cite costs ranging from $7,476 (rebuild estimate) to $10,000+ for out-of-warranty replacement. Many dealers falsely perform short-block shortcuts or software-only remedies without physical inspection. Compression testing showing 102 PSI has been dismissed by dealers as unrelated to recall despite matching recall symptoms.
Recalls/TSBs owners mention: Recall SC336 (21V-301) issued; Campaign 25V099 issued April 2025. Owners report recall remedy procedures changed mid-campaign without notice. Initial recall required engine replacement if vibration test failed; updated protocol requires software installation and borescope inspection. Some owners were denied coverage because their VIN was excluded from recall population, despite exhibiting identical defect symptoms. Kia has refused to honor recalls on grounds of maintenance record gaps, charging for diagnostics, or claiming no remedy available. PNSS software installation alone has not resolved failures in multiple reports; vehicles failed again shortly after, with some dealer notes stating 'recall repair caused the failure.' Owners report Kia citing 'hydrolocked engine' or water intrusion as grounds to void recall coverage.
Loss of motive power / stalling without warning in traffic
Engine stalls suddenly while idling, stopped at traffic lights, or while driving at highway speeds, with no warning lights and immediate restart difficulty or inability to restart. Often preceded by erratic idle RPM and check engine light.
When: Can occur early in vehicle ownership (23,750–53,000 miles) or later (85,000–128,000 miles); reported mid-December 2022 through June 2025.
Symptoms owners cite: Sudden engine stall at idle (traffic light, parked) without warning light; Complete shutdown during driving at 10–50 mph in traffic; Vehicle loses all electrical power momentarily (power steering loss, all warning lights flash); Check engine light illuminates before or after stalling event; Failure to restart immediately; requires multiple restart attempts or towing; Erratic RPM fluctuations at idle preceding stall; No low-oil warning despite oil-related root cause
Codes mentioned: P0014 (VVT timing failure), P0017 (Camshaft timing misalignment), P1327 (PNSS abnormal vibration detected), Check engine codes related to timing and compression loss
Repairs/costs cited: Dealers have blamed clogged air filters, low oil pressure, loosened oil filter, or water/moisture intrusion, recommending air filter replacement ($99–$200) or refusing to diagnose further. Owners report dealers refusing to perform recall-mandated PNSS test or oil consumption test, instead resetting codes and releasing vehicles. Some dealers cleared check engine lights without resolving root cause. No parts replacement typically documented in these repair notes; most are software updates or misdiagnosed repairs.
Recalls/TSBs owners mention: Recall SC336 addresses this symptom. However, many owners report dealers refusing to diagnose stalling as recall-related, marking recall complete based on PNSS software pass despite continued stalling. Some dealers state vehicles 'passed the tablet test' and therefore require no further action even though stalling persists. Owners report Kia corporate declining to escalate or arrange independent Field Service Engineer inspection; corporate cites that only dealership can request FSE review. Recall procedure changes mid-campaign resulted in some vehicles originally failing vibration test now passing under new protocol, leaving stalling unresolved. Multiple owners report being told stalling is not an engine issue and no loaner is guaranteed.
Complete engine seizure and loss of compression
Engine completely seizes, locks up, or loses all compression, often without any prior warning. Vehicle becomes immobilized and unsafe to drive. Compression tests reveal one or more cylinders at critically low PSI (e.g., Cylinder 3 at 102 PSI vs. normal 160+ PSI), consistent with piston ring damage and bore scoring.
When: Reported from 21,100 miles to 141,000 miles; some occur during highway driving at 50 mph, others at idle or low speeds.
Symptoms owners cite: Engine completely seizes and will not turn over; No restart possible; vehicle requires towing; Low or no measurable compression in one or more cylinders; Excessive cylinder wall scoring detected during inspection; Burning smell from engine bay during or after seizure event; Abnormal loud grinding, knocking, or rumbling from engine; Check engine light often illuminated immediately before seizure
Codes mentioned: Compression test results (e.g., Cylinder 3 102 PSI, well below minimum 160 PSI), P0014, P0017 (timing failure related to low compression), P1327 (PNSS abnormal vibration prior to seizure)
Repairs/costs cited: Dealers typically quote engine replacement ($7,476–$10,000+) or full rebuild. Some owners cite $7,476.32 rebuild estimate; out-of-warranty owners report denial of assistance and forced out-of-pocket repair. A few independent mechanics have attempted rebuilds, but failures recurred. Owners report dealers initially offering loaner vehicles, then reneging. Cost burden has fallen entirely on owners when recall not honored.
Recalls/TSBs owners mention: Recall SC336 (25V099) specifies free engine replacement for this symptom; however, owners report systematic denial. Common reasons for denial: VIN excluded from recall population despite matching defect symptoms; maintenance record gaps (missing 2022–2023 receipts despite recent oil changes); dealer falsely claiming 'recall repair caused the seizure, not covered'; compression test results dismissed as unrelated to recall. One owner cited 'out of warranty coverage' as reason for Kia refusing free repair on a recalled defect. Multiple owners report Kia corporate declining assistance after Kia dealer diagnosed failure related to recall.
Check engine light repeatedly illuminating with no consistent warning for low oil
Check engine light comes on intermittently or persistently, often with no accompanying low-oil pressure or low-oil level warning despite oil being critically low. Dealers reset code without repairing root cause; light returns within days.
When: Reported from 23,750 miles onward; some light remains on continuously, others flicker and are cleared by dealer.
Symptoms owners cite: Check engine light illuminates with no other warning lights active; No low-oil pressure warning illuminates despite dipstick being empty or nearly empty; No low-oil level warning despite oil consumption occurring; Light often cleared by dealer, then returns within days or weeks; Multiple trips to dealer to clear light without diagnosis; Flashing check engine light in some cases indicating severe condition
Codes mentioned: P0014 (Camshaft timing over-advanced), P0017 (Camshaft timing misalignment), P0420 (Catalyst system efficiency), P0004 (Fuel volume regulator control), P1327 (PNSS abnormal vibration)
Repairs/costs cited: Dealers typically clear code and release vehicle without diagnosis. Some charge diagnostic fees ($30–$100+) despite recall mandate. Owners report being told 'check engine light failed and has been repaired,' implying sensor malfunction rather than engine defect. No repairs documented in most cases; vehicle returned with light reilluminating shortly after.
Recalls/TSBs owners mention: Recall SC336 addresses check engine light combined with low compression and oil consumption. However, dealers routinely mark recall complete after PNSS software install and code reset without verifying if symptoms persist or if light remains. Owners report recall marked complete with check engine light still on. No follow-up inspection documented. Some dealers blame external causes (air filter, mice-eaten wires, water intrusion) and refuse to investigate oil-related codes.
Ineffective or incomplete recall remedy – PNSS software only without engine replacement
Dealerships install only the Piston-Ring Noise Sensing System (PNSS) software update without performing physical engine inspection, replacement, or addressing documented compression loss or stalling. Vehicle is marked recalled and complete despite persistent mechanical failure.
When: Documented in recalls completed April 2025 onward; failures recur within days to weeks of recall service.
Symptoms owners cite: Vehicle fails vibration test but passes when retested under updated protocol; Recall marked complete based on software install alone; Vehicle exhibits stalling, knocking, and rough running both before and after recall; Check engine light returns after recall service; Owner reports continued excessive oil consumption post-recall; P1327 code reappears after recall service
Codes mentioned: P1327 (Piston Ring Noise Sensing System fault reappears post-recall), P0014, P0017, P0420, P0004 (persist after software update)
Repairs/costs cited: PNSS software installed only; no engine parts replaced. Long Block Assembly (21101-QQK) not installed despite diagnosis indicating compression loss or timing failure. Owners allege dealers performed unauthorized 'short block' shortcuts, reusing contaminated camshafts, VVT solenoids, and valves. Some owners cite evidence that engine swap completed in 6.5 hours, which violates SC336 mandate requiring fluid flushes, software reflashing, and safety recalibrations—suggesting component reuse rather than full replacement.
Recalls/TSBs owners mention: Recall procedure changed mid-campaign without notification to owners. Initial recall remedy required engine replacement if vibration test failed. Updated procedure shifted to PNSS software installation with engine replacement only if abnormal sound is detected. Owners report vehicles originally failing vibration test now passing under new protocol. Some dealers state 'manager said we cannot do anything else' if tablet test passes, refusing borescope inspection or Techline escalation despite mechanical symptoms contradicting tablet result. Kia Corporate informed some owners that software update is sole remedy and no engine replacement is guaranteed even with confirmed low compression or stalling.
Dealership non-compliance and refusal to perform recall diagnostic testing
Dealerships refuse to perform recall-mandated diagnostic tests (PNSS, oil consumption, compression, borescope), misdiagnose symptoms as non-recall issues, charge customer fees for diagnostics covered by recall, clear codes without diagnosis, or release vehicles without completing recall inspection.
When: Ongoing throughout recall period (2021–2025); documented in complaints through June 2025.
Symptoms owners cite: Dealer performs visual inspection only (removing coils, checking battery) without teardown; Dealer refuses PNSS vibration test or oil consumption test upon owner request; Dealer performs 20-minute recall test despite protocol requiring full inspection; Dealer demands owner maintenance records as precondition for recall repair; Dealer charges $99+ diagnostic fee for exhaust back-pressure test (covered under recall); Dealer clears check engine code and marks recall complete without repair; Dealer releases vehicle with check engine light still illuminated; Dealer states no remedy available or repair not covered under recall
Codes mentioned: P1327, P0014, P0017, P0420, P0004 (codes cleared without root-cause diagnosis)
Repairs/costs cited: No repairs performed in most cases; only code clearing, air filter replacement (blamed as cause of stalling), or PNSS software update. Owners report dealers refusing to provide Techline Case Numbers, Engine Part Numbers, or time-stamped service records verifying correct Long Block installation. Some dealers withheld diagnostic data from Kia Techline, delaying safety remedy. Customers charged for diagnostics, oil changes, or air filter replacements on issues related to defective piston rings—costs ranging from $99 to $315.
Recalls/TSBs owners mention: Recall SC336 (25V099) mandates free inspection and engine replacement if symptomatic. However, dealers systematically refuse to diagnose or deny coverage on grounds of: (1) VIN not in recall population; (2) maintenance records unavailable or incomplete; (3) hydrolocked engine or water damage (owners claim no evidence); (4) external causes (clogged air filter, mice damage); (5) manufacturer instructed to deploy PNSS software only and not replace engine. Multiple owners report Kia corporate declining to escalate or dispatch Field Service Engineer for independent inspection. Kia states only dealership can request FSE, and dealership refuses. Some owners report dealer refusing to work on vehicle with broken ignition (from theft) until unrelated ignition repair completed, preventing recall access.
Synthesized from 143 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.