OBD-II Code P2406: EVAP Leak Detection Pump Sense Circuit High

What Does P2406 Mean?

The Powertrain Control Module (PCM) detected a fault in the evaporative emission (EVAP) system. Specifically, the voltage from the leak detection pump (LDP) sensor exceeds the expected range. This pump pressurizes the fuel system to check for vapor leaks. A 'Circuit High' signal indicates excessive voltage, preventing the PCM from verifying system integrity and triggering the Check Engine Light.

Technical definition: The SAE/OBD-II definition is "Evaporative Emission System Leak Detection Pump Sense Circuit High". The PCM registered a voltage reading from the EVAP leak detection pump's sense circuit above the manufacturer's specified range. This fault indicates a short-to-power in the wiring, a faulty pump sensor, or a PCM driver circuit failure.

Can I Drive With P2406?

⚠️Yes, But With Caution. Driving with code P2406 does not cause engine or transmission damage. However, your vehicle automatically fails emissions tests. The active Check Engine Light also masks new, potentially severe issues. Uncontained fuel vapors pose a minor fire risk near hot exhaust components. Fix the issue promptly to restore warning system functionality and emissions compliance.

Common Causes

• Damaged Wiring or Corroded Connector (Very Common) — The leak detection pump sits near the fuel tank, exposed to road salt, moisture, and debris. This exposure causes the wiring harness to chafe against the frame or the connector pins to corrode, creating a short-to-power circuit that sends high voltage to the PCM.
• Failed Leak Detection Pump (LDP) (Common) — The pump fails internally due to age, water intrusion, or liquid fuel saturation from chronically overfilling the gas tank. The integrated Hall-effect sensor shorts out, sending a constant high voltage signal even if the pump motor functions.
• Poor Ground Connection (Less Common) — The LDP requires a solid ground connection. A corroded or loose ground wire creates high resistance in the circuit, which the PCM interprets as a high voltage signal on the sense line.
• Rodent or Pest Damage (Less Common) — Soy-based wiring insulation attracts rodents. Chewed wires in the EVAP harness create a short in the sense circuit, triggering a P2406 code on vehicles parked outdoors for extended periods.
• Blown Fuse or Faulty Relay (Rare) — A fuse and relay protect the circuit powering the leak detection pump. A power surge or short blows the fuse or damages the relay, disrupting the circuit.
• Faulty Powertrain Control Module (PCM) or Software (Very Rare) — A fault in the PCM's internal driver circuit or a software glitch misinterprets the pump sensor signal. This requires exhaustive testing of wiring and the pump before replacing or reflashing the module.

Symptoms

• Check Engine Light is On — The Malfunction Indicator Lamp (MIL) stays illuminated as long as the fault is present.
• Failed Emissions Test — The EVAP monitor fails to run to completion, causing an automatic failure of state-mandated smog inspections.
• Fuel Smell — A faint smell of gasoline fumes surrounds the vehicle because the EVAP system cannot run diagnostic checks to contain them.
• EVAP System Warning Light — A separate warning light, resembling a gas cap icon or displaying "Check Fuel System," illuminates alongside the Check Engine Light.
• Difficulty Refueling — On specific models like Jaguars, LDP faults cause the fuel filler neck to build pressure, repeatedly clicking the gas pump nozzle off.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Repair Damaged Wiring or Connector — Parts: $10-$30, Labor: $150-$300, ~1.5 hr book time (Intermediate)
• Replace Leak Detection Pump (LDP) — Parts: $50-$300, Labor: $150-$250, ~1.2 hr book time (DIY)
  Volkswagen Jetta/Golf (2005-2010): OEM 1K0906201D (Alt: {'Dorman': '310-604 ($223)', 'Standard Motor Products': 'LDP18 ($418)', 'Wells': '4B1625 ($210)'})
  Volkswagen Jetta/Golf (2011-2014): OEM 7L0906243F (Alt: {'Bosch': 'W0133-5485222 ($67)', 'Dorman': '310-601 ($75)', 'Standard Motor Products': 'LDP49 ($101)'})
  Audi A4 (B7, 2005-2008): OEM 8E0906201K (Alt: {'Genuine': 'W0133-1926708 ($389)', 'Standard Motor Products': 'LDP63 ($386)'})
• Clean and Secure Connectors — Parts: $0-$10, Labor: $75-$150, ~0.5 hr book time (DIY)
• Replace Charcoal Canister Assembly — Parts: $250-$700, Labor: $150-$300, ~1.5 hr book time (Professional)
  Jaguar XJ (2010-2015): OEM C2D28280 (Canister w/ Pump)
  Toyota Corolla/Matrix (2005-2006): OEM 77740-02110
• Jaguar TSB JTB00436NAS2 Compliance — Parts: $400-$600, Labor: $1500-$2000, ~6 hr book time (Professional)
  Jaguar XJ (2010-2015): OEM C2D49253 (Protective Shield)

Used vs. New Parts: Buying Guide

When a used part is worth it: A used part suits older, high-mileage vehicles where a new OEM part is cost-prohibitive, provided the donor part shows no corrosion.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the donor vehicle did not fail emissions.
• Inspect the electrical connector for corrosion, brittleness, or water damage.
• Match the part number exactly to ensure correct internal calibration.

Decision logic:

• If The vehicle is less than 10 years old OR the new aftermarket part costs less than $100 → Buy new. Savings from a used part do not justify the risk of premature failure.
• If The pump integrates into the charcoal canister assembly → Buy new. Used canisters suffer contamination from overfilled fuel tanks.
• If The vehicle has a known TSB for external failure factors (e.g., Jaguar water intrusion) → Buy new and perform the complete TSB repair to prevent repeat failures.

Warranty tradeoff: Salvage yards offer 30-90 day warranties. New aftermarket parts provide 1-year to lifetime warranties. Dealer OEM parts carry 12-month/12,000-mile warranties.

Worst-case if a used part fails: $200-$500 if a used pump fails, requiring repeated diagnosis and labor.

What Happens If You Wait — Timeline

1. 0-1 month: Check Engine Light illuminates. The EVAP system self-test disables. Vehicle fails OBD-II emissions inspections. (MPG impact: 0%% · Added cost: $0)
2. 1-6 months: The active Check Engine Light masks new trouble codes. A cylinder misfire or transmission fault occurs without alerting the driver. (MPG impact: 0-1%% · Added cost: $0, but missing a new fault risks expensive catalytic converter damage.)
3. 6-18 months: Corrosion spreads to adjacent wires in the harness or nearby module connectors, creating complex electrical problems. (MPG impact: 0-1%% · Added cost: $200-$500 in additional wiring repairs.)
4. 18+ months: Secondary costs from masked serious fault codes cause catastrophic engine or transmission failure. (MPG impact: 0-1%% · Added cost: $2,000+ if a serious engine fault goes unnoticed.)

Cost of Not Fixing It

• 0-3 months: Automatic failure of emissions inspections. The active Check Engine Light masks new, potentially severe issues. (Added cost: Negligible, aside from re-inspection fees.)
• 3-12 months: A minor decrease in fuel economy (1-3%) occurs as the fuel tank fails to vent properly. (Added cost: $20-$60 per year in wasted fuel.)
• 12+ months: The primary long-term cost is the high risk of missing a new, damaging fault code. (Added cost: No direct costs, but missing a severe engine fault costs thousands.)

Diagnosis Steps

1. Read the Code and Freeze Frame Data
   Use an OBD-II scanner to confirm P2406 is active. Document related EVAP codes (e.g., P2401, P2402, P043E) and review freeze frame data to identify operating conditions when the fault occurred.
   Tools: OBD-II Scanner (Beginner)
2. Inspect Fuses and Relays
   Consult the owner's manual to locate the fuse box. Check fuses related to the EVAP system, emissions controls, or fuel system. A blown fuse indicates a short circuit requiring further investigation.
   Tools: Owner's Manual, Fuse Puller (Beginner)
3. Visually Inspect Wiring and Connectors
   Locate the leak detection pump near the charcoal canister. Inspect the wiring harness for chafing, melting, rodent damage, or green/white corrosion. Unplug the connector and check for bent or water-damaged pins.
   Tools: Flashlight, Safety Glasses, Mirror (Intermediate)
4. Test the Sense Circuit Voltage (Pro Tip)
   With the LDP connector unplugged and ignition on (engine off), use a multimeter to test the sense wire on the harness side. Baseline voltage should be near 0V or 0.5V. A constant reading above 4.0V confirms a short-to-power in the wiring harness. If normal, the issue lies within the pump.
   Tools: Digital Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
5. Check for Good Ground
   Use a multimeter set to Ohms to check continuity between the ground pin on the LDP connector (harness side) and a known good chassis ground. Readings under 1 Ohm are normal. An 'OL' reading indicates a bad ground requiring repair.
   Tools: Digital Multimeter (Intermediate)
6. Perform 'Wiggle Test' on Harness
   Reconnect the LDP connector and back-probe the sense wire. With the ignition on, gently wiggle the wiring harness from the pump toward the front of the vehicle. Voltage spikes identify the exact location of an intermittent short.
   Tools: Digital Multimeter with Back-Probes, Scan Tool (Advanced)
7. Activate the Pump with a Scan Tool
   Command the leak detection pump to turn on using bidirectional controls. Listen for the pump and watch sensor voltage data. If the pump runs but voltage remains fixed above 4.5V, the internal sensor failed.
   Tools: Bidirectional Scan Tool (Advanced)
8. Bench Test the LDP Motor Resistance
   Disconnect the LDP connector and measure resistance (Ohms) between the power and ground terminals on the pump. A healthy motor reads between 4 and 50 Ohms. An 'OL' (Open Loop) reading indicates a broken internal winding, requiring pump replacement.
   Tools: Digital Multimeter, Vehicle-Specific Repair Manual (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 45-85°F (At startup, for cold-start dependent tests.)
• Fuel Level: 15-85% (Ensures tank is not empty or full, which skews pressure readings.)
• Vehicle Speed: 40-65 mph (Steady cruise for 10 minutes allows the test to run.)
• Ambient Air Temp: 40-95°F (EVAP tests disable in extreme hot or cold weather.)

Related Codes

• P2401 — Indicates 'EVAP Leak Detection Pump Control Circuit Low'. It is the direct opposite of P2406, pointing to a short-to-ground or open circuit rather than a short-to-power.
• P2402 — Refers to the main control circuit powering the pump motor, not the sensor feedback circuit. Occurs alongside P2406 if major corrosion affects multiple wires in the connector.
• P0455 — Indicates a 'Gross EVAP Leak'. Triggered alongside P2406 because the electrical fault prevents the PCM from pressurizing the system, defaulting to a large leak assumption.
• P043E — Refers to 'EVAP System Leak Detection Reference Orifice Low Flow'. A failed pump sensor (P2406) cannot measure airflow through the reference orifice, triggering P043E as a secondary fault.

Climate & Environmental Factors

• Road Salt (Cold Climates): Vehicles in regions using road salt experience accelerated corrosion of the LDP's electrical connector, wiring insulation, and internal components, triggering shorts.
• High Humidity / Moisture: Damp climates or driving through high water introduces moisture into the LDP connector or pump housing, causing electrical shorts.

How to Talk to a Mechanic About This Code

Say this: "I have a Check Engine Light with code P2406, which is for the EVAP Leak Detection Pump Sense Circuit High. I need a diagnostic to determine if the cause is the wiring, the connector, or the pump itself before replacing parts."

Signals that you understand P2406 is an electrical code. Directs the shop to perform circuit diagnostics instead of quoting a new pump.

Avoid saying:

• 'My check engine light is on, can you look at it?' (Invites a broad, expensive diagnosis).
• 'I have an EVAP leak, can you fix it?' (Incorrect, P2406 is an electrical fault).
• 'Just replace the leak detection pump.' (Leads to misdiagnosis if wiring is at fault).

Questions to ask before authorizing the repair:

• Did you test the sense circuit wire for a short-to-power with the pump disconnected? What was the voltage reading?
• Did you check for corrosion in the connector and test the ground connection?
• Can you confirm the failure is the pump itself and not the wiring harness?
• Will the quoted price fix the P2406 code, and what is your warranty on this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended for TSBs or warranty work. Independent shops are more cost-effective for out-of-warranty vehicles.
  Best for: Vehicles under emissions or powertrain warranty., Vehicles with complex TSBs like the Jaguar XJ water intrusion issue., Newer vehicles requiring specialized diagnostic software.
  Downsides: Highest labor rates., Defaults to replacing expensive assemblies instead of targeted wiring repairs. (Typical cost: +50% vs. baseline)
• Independent Shop: Best overall fit. A shop with strong electrical skills diagnoses the circuit accurately, saving money over a dealer.
  Best for: Out-of-warranty vehicles., Diagnosing and repairing wiring issues like corrosion or chafing., Building a long-term relationship with a mechanic.
  Downsides: Electrical diagnostic expertise varies. Look for ASE certifications. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. P2406 requires specific electrical testing beyond a chain shop's scope, risking unnecessary part replacement.
  Best for: Simple maintenance like oil changes or tires.
  Downsides: Lacks in-depth electrical diagnostic training., Incentivized to sell parts rather than perform time-consuming diagnostics. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 50% of the car's private-party value, consider selling or trading in the vehicle.

• Car worth $5000, fix is $450: Fix it. The repair cost is under 10% of the car's value.
• Car worth $4000, fix is $2600: Walk away. The repair cost is 65% of the car's value.
• Car worth $2500, fix is $1500: Borderline. The repair exceeds 50% of the car's value. Consider replacement unless the car is in excellent condition.

What Scan Tool You Need for This Code

Minimum: A scanner that reads codes, clears codes, and displays live data for the EVAP system.

Basic code readers cannot display live voltage from the pump's sense circuit. Live data is essential to see if voltage is stuck high.

Budget: BlueDriver Pro (~$100) — Displays live data on a smartphone, allowing real-time monitoring of the LDP sense circuit voltage to confirm high readings.

Mid-range: Foxwell NT510 Elite (~$160) — Adds bidirectional control to command the leak detection pump on and off, definitively separating pump failures from wiring failures.

Professional: Autel MaxiCOM MK808 (~$500) — Offers full bidirectional control, OE-level diagnostics, and runs specific EVAP system tests.

Rent vs buy: Auto parts stores rent basic code readers, but they lack live data. Buying a tool like BlueDriver or Foxwell provides necessary diagnostic power.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the P2406 code.
2. Ensure the fuel tank is between 1/4 and 3/4 full.
3. Perform the vehicle-specific EVAP drive cycle.

Drive cycle (~20 minutes): A general EVAP drive cycle involves a cold start (sitting 8+ hours), idling for 2-3 minutes, driving at a steady speed (45-65 mph) for 10-15 minutes, and allowing the vehicle to cool down.

Readiness monitors affected: EVAP System Monitor, Catalyst Monitor, O2 Sensor Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery clears the code but resets all readiness monitors, guaranteeing an emissions test failure.
• The code returns immediately if the electrical fault remains.
• Failing to meet drive cycle prerequisites (e.g., fuel level, ambient temperature) prevents the EVAP monitor from running.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An illuminated Check Engine Light is an automatic failure. A complete drive cycle must set all readiness monitors before retesting.
• New York: The NYVIP3 inspection fails vehicles with an active P2406 code. Vehicles pass with one incomplete monitor, but active codes trigger hard failures.
• Texas: Counties requiring emissions testing fail vehicles with illuminated Check Engine Lights. Drive 50-100 miles after clearing codes to reset readiness monitors.

Most Commonly Affected Vehicles

• Jaguar XJ (2010-2015) — A design flaw allows water to enter the leak detection pump. Jaguar issued TSB JTB00436NAS2. The repair costs over $2,000 at a dealer due to 6 hours of labor required to drop the rear sub-frame.
• Volkswagen Jetta, Golf, Passat (2005-2012) — VW and Audi models commonly experience internal electrical faults in the Leak Detection Pump (LDP). Repair costs average $350 to $550.
• Audi A4, A6 (2005-2011) — Shares the same LDP and failure modes as Volkswagen. Wiring corrosion at the connector and internal pump failure are the primary causes.
• Land Rover Range Rover, LR3, Range Rover Sport (2006-2012) — Corrosion in the LDP connector or internal pump failure triggers P2406. The pump sits in a hard-to-reach area above the spare tire.
• Toyota Corolla, Matrix (2005-2006) — TSB EG002-06 indicates EVAP codes (P2401, P2402, P043E, P2406) require replacing the entire vapor canister assembly, which includes the pump.
• Hyundai Elantra, Accent (2005-2012) — Failures in the Diagnostic Module Tank Leakage (DM-TL) pump assembly trigger this code.
• BMW 3-Series, X-Series (2006-2015) — BMW uses a Diagnostic Module Tank Leakage (DMTL) pump. The Bosch OEM replacement (part 0261222018) resolves internal failures.
• Subaru Forester, Outback, Impreza (2005-2014) — Failed leak detection pumps frequently trigger this code. PZEV models may have extended warranty coverage.

Manufacturer-Specific Notes

• Jaguar: On 2010-2015 XJ models, P2406 stems from water intrusion. TSB JTB00436NAS2 requires replacing the pump, fuel filler pipe, and adding a protective shield, costing over $2,000.
• Volkswagen/Audi: These brands use an LDP prone to internal electrical failures. Many TDI models fall under the 'Dieselgate' extended emissions warranty, which covers this repair.
• Land Rover: The LDP sits in a tight space above the rear sub-frame or spare tire, making replacement difficult. Connector corrosion is highly prevalent.
• BMW: BMW refers to the LDP as a DMTL (Diagnostic Module Tank Leakage) pump. Search for 'DMTL Pump' to find correct parts and guides.
• Subaru: Vehicles sold in PZEV (Partial Zero Emission Vehicle) states carry an extended warranty for up to 15 years or 150,000 miles covering emissions components.

Real Owner Stories

2012 Range Rover Sport with P2402 & P2406

Check Engine Light illuminated with codes P2402 (Control Circuit High) and P2406 (Sense Circuit High).

What they tried:

1. Disconnected the electrical connectors for the LDP and purge valve.
2. Cleaned the pins with electrical contact cleaner.
3. Applied dielectric grease to seal out moisture.

Outcome: Cleared the codes. The Check Engine Light remained off after 200 miles. Cleaning fixed the high resistance issue.

Lesson: Clean electrical connectors first for 'Circuit High' codes in components exposed to weather. Corrosion causes high resistance faults.

2011 VW Jetta with recurring P2402

Check Engine Light appeared. A mechanic replaced the EVAP leak detection module.

What they tried:

1. A shop replaced the EVAP module (LDP).
2. The code returned after driving 100 miles.

Outcome: The fault was a short in the wiring harness, not the pump. The owner paid for an unnecessary part replacement.

Lesson: Do not automatically replace the pump for a circuit code. A returning code signals a wiring short-to-power.

2012 Jaguar XJ with P2406

Check Engine Light illuminated after a road trip with code P2406.

What they tried:

1. Researched the code and found Jaguar TSB JTB00436NAS2.
2. Confirmed the dealer repair cost over $2,600.

Outcome: The repair required replacing the LDP/canister, fuel filler tube, and adding a protective shield by dropping the rear sub-frame.

Lesson: Check for TSBs before starting diagnosis. Known design flaws require specific, often expensive, repairs.

2014 Subaru Impreza PZEV model

Vehicle experienced an emissions issue at 144,000 miles.

What they tried:

1. Discovered PZEV models carry extended emissions warranties in states like CA, NY, and MA.

Outcome: Subaru fully covered the repair under the 15-year/150,000-mile PZEV warranty.

Lesson: Check warranty coverage for PZEV-designated vehicles in participating states before paying for emissions repairs.

How to Prevent This Code From Triggering

• Apply Dielectric Grease to Connectors (Any time a connector is disconnected, or every 2-3 years in salt-belt regions.) — Dielectric grease seals out moisture and salt, preventing metal pin corrosion that causes 'Circuit High' faults.
• Perform Regular Undercarriage Washes (Monthly, especially during winter in cold climates.) — Washing removes road salt and corrosive grime from wiring harnesses and EVAP components, slowing corrosion.
• Inspect and Secure Wiring Harnesses (During any under-vehicle service.) — Ensures wiring harnesses do not rub against the frame. Chafing wears through insulation and causes shorts.
• Avoid Overfilling the Fuel Tank (Every fill-up.) — Topping off forces raw fuel into the charcoal canister, saturating and damaging sensitive electrical components like the LDP.
• Use Rodent Deterrent Measures (If vehicle is parked outdoors for extended periods.) — Deterrents prevent rodents from chewing soy-based wire insulation and causing shorts.

Frequently Asked Questions

Can I drive my car with a P2406 code?

Yes, driving is safe and will not affect engine performance. However, you will fail emissions tests. The Check Engine Light also masks other potential warnings.

Can a loose gas cap cause a P2406 code?

No. A loose gas cap causes leak-related codes like P0455 or P0457. P2406 is an electrical 'Circuit High' code related to the pump's sensor.

What is the difference between a circuit code like P2406 and a leak code like P0455?

A circuit code indicates an electrical problem like a short or open wire. A leak code indicates a physical leak in the fuel vapor system. You must fix electrical faults before the system can test for leaks.

What is the most common misdiagnosis for P2406?

The most common mistake is replacing the leak detection pump without testing the wiring. The fault is often a short-to-power in the wiring harness. A new pump will not fix a wiring problem.

I replaced the leak detection pump and the P2406 code came back. What now?

If a new pump fails to fix the issue, the problem is a wiring short or a faulty PCM. Test the sense circuit for a short-to-power, ensure the ground connection is clean, and verify connector pins make contact. If all wiring tests pass, the PCM requires testing.

How much does it cost to fix P2406?

Costs depend entirely on the root cause. Cleaning a connector costs under $100, while wiring repairs average $150-$300. Replacing the leak detection pump ranges from $200 to $600, though complex TSB repairs on luxury vehicles exceed $2,000.

Is this a difficult repair to do myself?

Replacing the pump is a straightforward DIY job if easily accessible. Accurately diagnosing the electrical circuit requires a multimeter and wiring diagrams, making it difficult for beginners. Misdiagnosis leads to buying unnecessary parts.

Will clearing the code make it go away?

Clearing the code temporarily turns off the light, but it returns once the PCM runs the EVAP system test. The underlying electrical problem requires repair.

Can overfilling my gas tank cause a P2406 code?

Chronically topping off the tank forces raw fuel into the charcoal canister. This saturates components and damages sensitive electrical parts like the LDP over time.

What are the long-term consequences of ignoring P2406?

Ignoring the code guarantees failed emissions tests and leaves the Check Engine Light on. This masks new, serious problems that could cause catastrophic engine damage.

Key Takeaways

• P2406 is an electrical fault, not a physical leak, indicating the leak detection pump's sense circuit voltage exceeds the normal 0.5V-2.5V range.
• Damaged wiring and corroded connectors near the fuel tank cause over 60% of P2406 codes, heavily outnumbering actual pump failures.
• Driving with P2406 is safe for the engine, but guarantees an automatic emissions test failure and masks new, potentially catastrophic warning lights.
• Test the sense circuit for a short-to-power (readings above 4.0V) and verify ground resistance is under 1 Ohm before spending $200+ on a replacement pump.
• Owners of 2010-2015 Jaguar XJ models face a known water intrusion defect (TSB JTB00436NAS2) requiring a $2,000+ repair involving rear subframe removal.