P0302 Code: Nissan Altima (2019-2023) - Causes, Symptoms & Fixes

Comprehensive diagnostic guide for OBD-II code P0302 on 2019-2023 Nissan Altima

Note on data: Based on the provided NHTSA data for 2019-2023 Nissan Altima, there are no owner complaints and no recalls found in the database for this combination. No recalls found in NHTSA database. This guide uses general automotive diagnostic knowledge in addition to the code meaning, and clearly states data limitations.

CODE MEANING AND SEVERITY

• What P0302 means: Cylinder 2 misfire detected. The engine control module (ECM/PCM) has detected that cylinder 2 is not combusting properly, which can be caused by ignition, fuel, mechanical health, or air/valve issues.
• Severity (general guidance):
  • Intermittent misfire with light symptoms: may be benign but should be diagnosed to prevent catalyst damage and unnecessary emissions.
  • Persistent or frequent misfire: can cause rough running, increased emissions, reduced fuel economy, potential catalytic converter damage, and possible engine damage if ignored long enough.
• Why Altima users see it: The 2019-2023 Altima uses a distributed ignition and fuel system; a misfire in any cylinder can trigger P0302 specifically if cylinder 2 is consistently failing.

COMMON CAUSES ON NISSAN ALTIMA

• Ignition system
  • Faulty spark plug in cylinder 2 (worn, fouled, oil fouled, incorrect gap)
  • Faulty ignition coil on cylinder 2 (coil-on-plug) or weak coil due to internal short
  • Damaged ignition coil boot or wiring to coil in cylinder 2
• Fuel system
  • Dirty or failing fuel injector for cylinder 2 (coating, clog, opening/closing issue)
  • Low fuel pressure affecting injector performance (less common as sole cause, but possible)
  • Electrical driver issue to injector (if coil-injector assembly shares circuitry)
• Air and vacuum
  • Vacuum leak near cylinder 2 intake port or plenum, or a cracked/loose vacuum hose
  • Intake manifold gasket issues around cylinder 2
• Mechanical/engine health
  • Low compression in cylinder 2 due to worn rings, valve seat, valve derailment, or head gasket issue
  • Timing issues (rare for a misfire-only symptom but possible in some engines)
• Sensors and drivability
  • Dirty MAF/MAF sensor readings or other air metering anomalies can contribute to misfire perception
  • Mass air flow, O2 sensor, or ECU sensor interpretation issues are less common as sole causes but can accompany misfire conditions
• Other possibilities
  • Contaminated or incorrect fuel (fuel quality affects combustion)
  • Misrouted or loose fuel/ignition harness connections to cylinder 2

SYMPTOMS

• Common symptoms (may be subtle or pronounced):
  • Rough idle or vibration when the engine is at idle or low rpm
  • Hesitation or stumbling during acceleration
  • Decreased engine performance and drivability
  • Reduced fuel economy
  • Check Engine Light (CEL) illuminated with P0302
  • Possible engine shudder under load or at idle
  • In some cases, there may be no obvious symptoms outside of a CEL
• Note: If P0302 occurs with another misfire code (e.g., P0300, P0301, P0303, P0304), symptoms may be more noticeable due to multiple cylinders misfiring.

DIAGNOSTIC STEPS

Start-to-finish approach (structured for a typical shop or a handy DIYer with a capable scan tool)

Step 0 — Confirm and prepare

• Confirm P0302 in a proper scan tool (not just a generic code reader). Check freeze-frame data: RPM, MAP/MAF readings, fuel Trim, engine load, and speed at the moment of misfire.
• Note any related codes (P0300, P0301, P0303, P0304, or P0171/P0174 for fuel trim issues).
• Check for service bulletins or recalls only if data allows; per the provided data, “No recalls found in NHTSA database.”

Step 1 — Initial physical inspection

• Inspect cylinder 2 spark plug: look for fouling, oil contamination, electrode wear, improper gap.
• Inspect spark plug boot and coil connection for damage, oil intrusion, or corrosion.
• Inspect wiring harnesses to coil and injector for signs of abrasion, heat damage, or loose connections.
• Visually inspect for vacuum leaks around the intake manifold near cylinder 2 and adjacent hoses.

Step 2 — Spark plug and ignition component test

• Spark plug: if worn or fouled, replace with the correct plug type and gap. Establish a baseline after replacement.
• Coil-on-plug (cylinder 2): check resistance if you have the specs, though many DIYs substitute with a known-good coil as a test.
• If a misfire stops after swapping coils (see Step 3), the issue is likely coil-related.

Step 3 — Swap test (to identify coil vs. injector vs. mechanical issue)

• Coil swap test: Move the Cylinder 2 coil to Cylinder 1 (or 4) and move Cylinder 1 coil to Cylinder 2 (or do a cross-swap). Road test or idle test to see if the misfire follows the coil.
  • If the misfire appears in Cylinder 1 after the swap, the coil is likely the culprit (faulty coil on that cylinder).
  • If the misfire remains on Cylinder 2 despite coil swapping, the coil is likely OK; focus on injector, wiring, or mechanical factors.
• Injector test: If you have access to a noid light and a way to switch injectors (swap inj 2 with inj 1), perform a swap to see if the misfire follows the injector.
  • If the misfire moves with the injector, the injector is suspect.
  • If the misfire stays on Cylinder 2, the injector may be OK; proceed to compression and air leaks tests.

Step 4 — Electrical and sensor checks

• Check injector power and signal with a diagnostic tool; verify proper injector pulse width and duty cycle for cylinder 2.
• Check for any ECM/PCM software updates or abnormal sensor readings that could contribute to misfire behavior (MAP/MAF, O2 sensors, etc.), though these are less direct causes for P0302 alone.

Step 5 — Air and vacuum checks

• Perform a spray test around the intake manifold ports and hoses to identify vacuum leaks. Slight changes in idle when spraying around cylinder 2 area can indicate a gasket or leak issue.
• Inspect PCV system and related lines for leaks or sticking valves.

Step 6 — Mechanical integrity check

• Perform a compression test on cylinder 2 (and ideally on all cylinders for comparison).
• If cylinder 2 shows low compression or a significant discrepancy with others, investigate valve seating, piston rings, head gasket, or leakage paths.
• If compression is normal, prioritize ignition and fuel delivery path, then revisit injector and wiring issues.

Step 7 — Post-diagnosis validation

• After swapping/repair, clear codes and run the engine to confirm P0302 does not return.
• If P0302 returns, re-evaluate the remaining components: coil, injector, and a potential valve or compression fault.
• If still unresolved, consider professional inspection, as specialized scope tools or component testing may be required.

RELATED CODES

• P0300: Random/Multiple Cylinder Misfire Detected
• P0301: Cylinder 1 Misfire Detected
• P0303: Cylinder 3 Misfire Detected
• P0304: Cylinder 4 Misfire Detected
• Note: In a four-cylinder Altima, P0305 or P0306 would be out of scope; focus on the above if they appear in conjunction with P0302.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices are approximate and depend on location, labor rates, and exact parts used. Values exclude tax and core charges.

• Spark plug replacement (cylinder 2)

  • Parts: ~$4–$25 per plug (OEM or aftermarket)
  • Labor: ~0.4–0.8 hours
  • Typical total: ~$60–$140

• Ignition coil replacement (cylinder 2)

  • Parts: ~$60–$180 for a single ignition coil
  • Labor: ~0.6–1.0 hours
  • Typical total: ~$140–$300

• Fuel injector replacement or cleaning (cylinder 2)

  • Injector cleaning (service): ~$50–$150
  • New injector (per cylinder): ~$50–$150
  • Labor: ~0.5–1.0 hours
  • Typical total: ~$100–$350

• Vacuum leak repair or intake gasket/PCV repair (cylinder vicinity)

  • Parts: ~$20–$150 depending on hose/gasket
  • Labor: ~0.5–1.5 hours
  • Typical total: ~$100–$350

• Compression/head gasket/valve issues

  • Parts: highly variable, from gasket kit to full valve job
  • Labor: many hours
  • Typical total: $1,000–$4,000+ (often necessary only if compression test fails)

• Miscellaneous and incidental costs

  • Software/SCOP updates, connectors, replacement fasteners: $10–$100
  • Diagnostics/inspection fee: $60–$120 (varies by shop)

Important notes on costs:

• The estimates above assume a typical 2.5L four-cylinder Altima. Local labor rates and availability of OEM vs. aftermarket parts will affect pricing.
• If multiple components are found faulty (e.g., coil + injector), costs will increase accordingly.
• DIY labor can greatly reduce costs if you’re comfortable with the tasks (spark plug replacement, coil swap, basic testing). However, certain tests (compression, injector testing with noid light, diagnosis with scope) may require professional tools.

DIY VS PROFESSIONAL

• DIY options (cost-conscious, requires proper tools):
  • Replace cylinder 2 spark plug(s) and inspect the coil boot.
  • Swap coil between cylinders to assess whether the coil is the culprit.
  • Inspect wiring harnesses and visually check injector wiring and vacuum hoses.
  • Use a noid light to verify injector signal if you have access to one; perform a basic compression test if you have a compression gauge.
  • Pros: low cost, educational, can fix simple issues quickly.
  • Cons: limited diagnostics for fuel delivery, compression testing, and accurate injector testing; risk of misdiagnosis if you lack tools.
• Professional options (recommended for thorough resolution):
  • Comprehensive diagnostic using a scan tool to view live injector duty cycles, misfire counts, fuel trims, and ignition timing.
  • Controlled compression test with proper equipment and safety practices.
  • Test and verify harness integrity, injector flow, and possible mechanical issues.
  • Pros: higher likelihood of correctly identifying root cause; documentation and warranty on repairs.
  • Cons: higher upfront cost.

PREVENTION

• Regular maintenance
  • Replace spark plugs at manufacturer-recommended intervals with the correct heat range and gap for the 2.5L engine.
  • Use high-quality ignition coils or OEM replacements if coil failure is common for your vehicle’s history.
  • Keep air intake and MAF sensor clean and calibrated; replace air filter on schedule.
• Fuel system care
  • Use good quality fuel and consider a fuel system cleaner occasionally to help prevent injector deposits.
  • Address stale fuel and ethanol-related issues promptly.
• Vacuum system and gaskets
  • Inspect hoses and the intake manifold gasket periodically; replace cracked hoses or smoking vacuum lines to prevent leaks.
• Driving habits
  • Regular(ish) longer drives help burn off deposits and keep injectors, valves, and ignition components in good condition.
• Early issue resolution
  • If you notice rough idle, hesitation, or reduced performance, diagnose early to prevent misfire-related catalyst damage.

DATA LIMITATIONS

• The provided dataset indicates no owner complaints and no recalls for 2019-2023 Nissan Altima related to P0302. Therefore, this guide relies on general diagnostic knowledge and standard misfire troubleshooting rather than documented manufacturer-initiated advisories specific to this model/year. If new data appears (complaints, recalls, or TSBs), adjust the approach accordingly.