P2406 — Evaporative Emission System Leak Detection Pump Sense Circuit High

OBD2 code P2406 flags a problem with the evaporative emission (EVAP) system (evaporative emission system leak detection pump sense circuit high). The car is usually drivable while you plan the repair. Common culprits: faulty purge valve (canister purge solenoid), loose, damaged or wrong fuel cap, small leak in the fuel tank or filler neck.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK Safe to drive. EVAP faults affect emissions, not drivability — you can keep using the car while planning the repair. Fuel vapour smell is a reason to fix it sooner: vapours are flammable and harmful.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm P2406 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the evaporative emission (EVAP) system for damage, corrosion, chafing or poor contact.
  4. Subsystem check With the evaporative emission system leak detection pump sense disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
  5. Subsystem check Check the fuel cap first — it is the most common cause; inspect the seal and tighten until it clicks.
  6. Subsystem check Run an EVAP leak test (smoke test) to locate small leaks in hoses, canister and valves.
  7. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2406 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P2406 (parts and labor, USD, independent shop rates): Replace the fuel cap: $20–$60; Replace the purge or vent valve: $120–$350; Replace the charcoal canister: $250–$700. Overall, fixing P2406 usually costs between $20 and $700. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Is it safe to drive with P2406?

Safe to drive. EVAP faults affect emissions, not drivability — you can keep using the car while planning the repair. Fuel vapour smell is a reason to fix it sooner: vapours are flammable and harmful.

What is the most common cause of P2406?

The most common causes are: faulty purge valve (canister purge solenoid), loose, damaged or wrong fuel cap, small leak in the fuel tank or filler neck.

How do I diagnose P2406 myself?

Start with a scan: confirm P2406, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the evaporative emission system leak detection pump sense, and verify the suspect component against live data before buying parts.

Will P2406 clear itself?

Sometimes P2406 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

How much does it cost to fix P2406?

Replace the fuel cap — $20–$60; Replace the purge or vent valve — $120–$350; Replace the charcoal canister — $250–$700. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does P2406 mean?

Seeing P2406 on your scanner? The control unit has caught the evaporative emission (EVAP) system operating outside its calibrated window. The formal description is “Evaporative Emission System Leak Detection Pump Sense Circuit High”, and the code is grouped under powertrain (engine/transmission) faults.

“Circuit high” means the control module sees a voltage on the evaporative emission system leak detection pump sense circuit that is above the expected range — typically close to battery voltage. Physically this points to a short to a power feed, a broken ground return, or a failed component pulling the signal line high.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores P2406 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

Common symptoms of P2406

  • fuel smell near the car, especially after refueling
  • no noticeable driving symptoms in most cases
  • slightly worse fuel economy
  • difficulty refueling (nozzle clicks off)
  • Check Engine Light on

What causes P2406?

  • open ground return of the evaporative emission system leak detection pump sense
  • signal wire shorted to battery positive
  • failed evaporative emission system leak detection pump sense pulling the signal high
  • saturated or damaged charcoal canister
  • faulty vent valve or leak detection pump
  • loose, damaged or wrong fuel cap
  • cracked EVAP hoses or lines
  • small leak in the fuel tank or filler neck

How to diagnose P2406

  1. Connect an OBD2 scanner, confirm P2406 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Visually inspect the wiring harness and connectors related to the evaporative emission (EVAP) system for damage, corrosion, chafing or poor contact.
  4. With the evaporative emission system leak detection pump sense disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
  5. Check the fuel cap first — it is the most common cause; inspect the seal and tighten until it clicks.
  6. Run an EVAP leak test (smoke test) to locate small leaks in hoses, canister and valves.
  7. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2406 does not return.

How to fix P2406

Start with the cheapest and most common causes before replacing expensive parts:

  • Replace the fuel cap — $20–$60
  • Replace the purge or vent valve — $120–$350
  • Replace the charcoal canister — $250–$700

How much does it cost to fix P2406?

Repair cost depends on which component actually failed. Typical scenarios for P2406 (parts and labor, USD, independent shop rates):

  • Replace the fuel cap: $20–$60
  • Replace the purge or vent valve: $120–$350
  • Replace the charcoal canister: $250–$700

Overall, fixing P2406 usually costs between $20 and $700. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with P2406?

Safe to drive. EVAP faults affect emissions, not drivability — you can keep using the car while planning the repair. Fuel vapour smell is a reason to fix it sooner: vapours are flammable and harmful.

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