P0440 Code: Nissan Altima (2019-2023) - Causes, Symptoms & Fixes

No recalls found in NHTSA database.

Owner complaints: No NHTSA complaints found for this make/model/year/issue combination.

This guide provides a comprehensive diagnostic approach to P0440 (Evaporative Emission Control System Malfunction) specifically for 2019–2023 Nissan Altima. Given the provided data, there are no listed recalls or complaints to rely on for this exact combination, so diagnostic guidance relies on general EVAP knowledge plus model-typical Nissan Altima layouts.

1. CODE MEANING AND SEVERITY

• Code: P0440 — Evaporative Emission Control System Malfunction
• What it means: The engine control module (ECM) detected an issue with the EVAP system that could allow fuel vapors to escape or not be properly controlled. This is an emissions-related fault.
• Severity: Emissions-related; typically triggers a malfunctioning MIL (Check Engine Light) and may cause your vehicle to fail a sniff-test or idle/emissions-related inspections. It is not typically a direct safety risk (like braking or steering), but ignoring it can lead to more expensive repairs if an evaporative leak worsens.
• Likelihood of failure modes: Leaks or faults within the EVAP system can be small (tiny leaks) or large (canister-related). P0440 is a generic catch-all for EVAP issues that don’t map to a more specific subcode.

2. COMMON CAUSES ON NISSAN ALTIMA

• Loose, damaged, or improperly seated fuel cap (including missing vent or cracked seal)
• Cracked, split, or loose EVAP hoses and vacuum lines
• Faulty purge valve (also called purge solenoid) or its electrical circuit
• Faulty vent valve (if equipped) or its circuit
• Leaking or failed charcoal canister
• Faulty leak detection pump (LDP) or its wiring (if the vehicle uses an LDP for EVAP leak testing)
• Damaged or corroded EVAP system seals, gaskets, O-rings
• Wiring harness or sensor issues affecting EVAP purge sensor, pressure sensor, or EVAP related actuator circuits
• Prior service errors (unplugged connectors, incorrect routing of hoses) after maintenance

3. SYMPTOMS

• Check Engine Light (MIL) on or flashing
• Failed emissions test or inspection
• Subtle fuel odor or gasoline smell around the vehicle (especially if a leak exists)
• Possible rough idle only if the leak affects engine vacuum significantly (less common with small leaks)
• Engine may run normally otherwise; drivability typically unaffected unless a large leak or multi-issue condition exists
• Occasional EVAP test failures during on-board diagnostics (especially during drive-cycle)
• In some cases, no obvious symptoms other than the MIL

4. DIAGNOSTIC STEPS
   Note: Work safely around fuel systems. If you’re not comfortable, seek a qualified tech.

• Step 1: Confirm the code and record data

  • Use a scan tool to verify P0440 and check for any accompanying codes (P0440 often appears with P0442, P0441, P0455, P0456, etc.). Freeze-frame data can help identify engine load, fuel trim, and other context.

• Step 2: Inspect the basics

  • Gas cap: Ensure it is the correct, OEM-cap or a high-quality cap. Tighten until it clicks; replace if cracked, warped, or missing the seal. Re-run the drive cycle to see if the code returns.
  • Visual EVAP plumbing: Look for obvious damage, disconnected hoses, pinched lines, or signs of wear around the EVAP plumbing, especially near the canister, purge valve, and close to the wheel wells.

• Step 3: Inspect and test the purge valve and vent valve circuits

  • Electrical check: With ignition OFF, inspect the fuse and relay for the purge valve and vent valve; check the wiring harness for corrosion, open circuits, or loose connectors.
  • Functional check: Using a scan tool, command the purge valve to operate (open and close) with the engine running or in a key-on/engine-off state as allowed by the tool. Listen for a click and verify vacuum is being drawn on the intake manifold when commanded. A stuck valve can cause P0440.
  • Vacuum/pressure check: With engine running (and using proper safety precautions), inspect for vacuum at the purge line when commanded. If no vacuum is present, the purge valve or associated line could be failing.

• Step 4: EVAP canister and leak testing

  • Visual canister/lines: Inspect the charcoal canister and hoses for cracks or swelling.
  • Smoke test or pressure decay test: The most reliable way to locate EVAP leaks is a smoke machine: seal the system and introduce smoke to the EVAP plumbing; look for smoke escaping at hoses, canister, or fittings.
  • Leaks and canister: If you find a leak around hoses, clamps, or canister connections, repair or replace as needed. If no external leak is found, the issue may be an internal canister fault or LDP issue.

• Step 5: Leak Detection Pump (LDP) and related sensors

  • If equipped, test LDP operation according to the service manual. Check for proper wiring, ground, and signal to the ECM.
  • Inspect the EVAP pressure sensor (if present) for correct readings and wiring integrity.

• Step 6: Cross-check for related codes

  • If P0440 is accompanied by P0442 (small leak) or P0455 (gross leak), tailor the diagnostic approach toward the indicated leak size.
  • If no leaks are found, consider testing the canister integrity and purge/vent valve operation more thoroughly, as intermittent faults can be difficult to pinpoint.

• Step 7: Verify repair and clear codes

  • After repairs, reset the codes and perform a drive cycle to ensure the EVAP monitor completes and no new codes appear. Some Altima models require specific drive patterns to re-run EVAP tests.

5. RELATED CODES

• P0441 - Evaporative Emission Control System Incorrect Purge Flow
• P0442 - Evaporative Emission Control System Small Leak
• P0443 - Evaporative Emission Control System Balance Incorrect
• P0445 - Evaporative Emission Control System purge error (alternate variant)
• P0446 - Evaporative Emission Control System Vent Control Circuit
• P0455 - Evaporative Emission Control System Large Leak
• P0456 - Evaporative Emission Control System Very Small Leak
• P0457 - Evaporative Emission Control System Very Small Leak Detected
• P0450 – P0459 range (other EVAP-related codes)
  Note: These codes are commonly related to EVAP or similar systems and may appear in conjunction with P0440 depending on the specific fault.

6. REPAIR OPTIONS AND COSTS (2025 PRICES)
   Prices vary by region, labor rate, and parts source. The ranges below are approximate and reflect typical consumer repair costs. Taxes and shop fees not included.

• Gas cap replacement

  • Parts: $8–$40
  • Labor: 0.1–0.3 hr
  • Typical total: $25–$80
  • Notes: Often resolves P0440 if the cap was the issue.

• EVAP purge valve replacement (Nissan Altima)

  • Parts: $40–$180
  • Labor: 0.3–1.0 hr
  • Typical total: $150–$400
  • Notes: Common fix for P0440; improvement usually straightforward.

• EVAP vent valve replacement (if equipped)

  • Parts: $50–$180
  • Labor: 0.3–1.0 hr
  • Typical total: $120–$420

• Charcoal canister replacement

  • Parts: $250–$650
  • Labor: 1.5–3.0 hr
  • Typical total: $600–$1,200
  • Notes: More expensive; consider before replacing if no leaks found elsewhere.

• Leak Detection Pump (LDP) replacement (if present)

  • Parts: $150–$400
  • Labor: 0.5–2.0 hr
  • Typical total: $300–$900
  • Notes: Sometimes difficult to diagnose; check electrical harness first.

• EVAP system leak repair (hoses, clamps, fittings)

  • Parts: $10–$100
  • Labor: 0.2–1.0 hr
  • Typical total: $60–$350
  • Notes: Inexpensive leaks often result from cracked hoses or loose clamps.

• EVAP system diagnostic and leak test (shop service charge)

  • Parts: N/A
  • Labor: 0.5–2.0 hr
  • Typical total: $100–$250
  • Notes: If you bring the vehicle to a shop, you may incur a diagnostic fee unless waived with a repair.

7. DIY VS PROFESSIONAL

• DIY-friendly scenarios:
  • Gas cap replacement
  • Visual hose/clamp fix on simple, accessible lines
  • Replacing a faulty purge valve if you have the right tool set and can safely access it
• Professional-recommended scenarios:
  • Suspected leaks in charcoal canister, LDP, or hard-to-find hose failures
  • EVAP system smoke testing or pressure testing
  • Electrical testing of purge/vent valve circuits and related wiring
  • If the vehicle has a confirmed leak but you cannot locate it with a smoke test
• Notes:
  • EVAP work involves fuel vapors and precise diagnostics; improper handling can cause further issues or safety concerns.
  • Some tasks require specialized equipment (smoke machine, precise vacuum/pressure gauges, OEM wiring diagrams).

8. PREVENTION

• Keep the fuel cap snug and use a high-quality, properly rated cap; replace if worn or damaged.
• Avoid damaging underbody EVAP hoses by road debris or collisions; inspect hose routes during routine maintenance.
• Schedule periodic EVAP system inspections during regular service visits, especially if the MIL is on or there are odors.
• If your Altima has an EVAP sensor or LDP, ensure electrical connectors are clean and secure; loose connections can trigger false failures.
• Address small EVAP-related codes promptly to avoid progression to larger issues; address any persistent leaks quickly.
• If you perform repairs, ensure all clamps and hose connections are retried and re-sealed correctly after replacement.

Data limitations and transparency

• The provided data shows no NHTSA owner complaints or official recalls for 2019–2023 Nissan Altima related to P0440. Therefore, this guide does not rely on vehicle-specific recall-based failure patterns and instead uses general OBD-II EVAP system knowledge applied to the Altima platform.
• Prices are approximate as of 2025 and vary by region, dealer vs aftermarket parts, and labor rates. Your actual cost may differ.
• If you need more model-specific steps (e.g., exact valve locations or harness routing for your VIN), consult the Nissan service manual or a Nissan dealer technician.