P2406 — Evaporative Emission System Leak Detection Pump Sense Circuit #

Note: The wording of this trouble code may differ depending on the vehicle manufacturer.

• Evaporative Emission System Leak Detection Pump Sense Circuit High (BMW, Chrysler, Ford, GM, Toyota)
• EVAP System Leak Detection Pump Sensor Circuit High (Volkswagen, Audi)
• EVAP LDP Sensor Circuit High Input (Jeep, Dodge)

Summary of the P2406 Code #

The P2406 diagnostic trouble code (DTC) relates to the Evaporative Emission System (EVAP), specifically indicating a problem with the Leak Detection Pump (LDP) Sense Circuit. The EVAP system is designed to capture and recycle fuel vapors from the tank, preventing them from escaping into the atmosphere. The LDP is an electrically operated pump that pressurizes the EVAP system to check for leaks, and the sense circuit monitors its operation. When the Engine Control Module (ECM) or Powertrain Control Module (PCM) detects voltage in the LDP sense circuit higher than expected, it triggers the P2406 code. Depending on the vehicle, this issue can cause emissions test failures and may impact drivability.

Common Symptoms for Code P2406 #

While the P2406 code often presents with few immediate symptoms, some drivers may notice subtle changes in vehicle behavior. Being vigilant about these signs can help avoid further complications:

• Check Engine Light illuminated on the dashboard
• Failed emissions tests
• Slight decrease in fuel efficiency
• Possible fuel odor, especially near the fuel tank area
• Occasional rough idle or hesitation (less common)
• No noticeable symptoms in many cases

Most Likely Causes for Code P2406 #

The P2406 code is typically triggered by electrical or sensor-related issues within the EVAP leak detection pump circuit. The following are the most common causes, ordered by likelihood:

1. Faulty Leak Detection Pump (LDP) Sensor
2. Wiring issues (corroded, damaged, or shorted wires in the LDP sense circuit)
3. Defective Leak Detection Pump itself
4. Poor electrical connections at the LDP or ECM/PCM
5. ECM/PCM malfunction (rare)

Step-by-Step Diagnosis for Code P2406 #

Diagnosing the P2406 code requires a systematic approach, as several components could be at fault. Here are the recommended steps to pinpoint the problem:

• 1. Verify the code with a professional OBD-II scanner and check for additional codes.
• 2. Visual inspection: Examine the wiring and connectors at the leak detection pump and related circuits for signs of corrosion, damage, or loose connections.
• 3. Test the LDP sensor using a digital multimeter to verify resistance and voltage according to OEM specifications.
• 4. Check leak detection pump operation: Use a scan tool or manufacturer procedure to command the pump ON and monitor sensor readings.
• 5. Inspect ECM/PCM connections for bent pins, corrosion, or moisture intrusion.
• 6. Clear the code, then perform a drive cycle to see if the code returns after repairs or component replacements.

Possible Repairs for Code P2406 #

Repairs should directly address the root cause identified during diagnosis. Depending on findings, typical solutions include:

• Repair or replace damaged wiring or connectors in the LDP sense circuit
• Replace the faulty leak detection pump sensor
• Replace the entire leak detection pump assembly (if sensor is integrated)
• Clean and secure all electrical connections related to the EVAP system
• In rare cases, reprogram or replace the ECM/PCM if confirmed defective

Can You Drive with Code P2406? #

Yes, you can usually drive with code P2406 for a limited time, as it rarely causes immediate drivability issues or safety concerns. However, ignoring the code can lead to failed emissions tests and may allow fuel vapors to escape, increasing pollution. For best results—and to prevent long-term damage or additional codes—address the cause as soon as possible.

Vehicles Most Commonly Affected by P2406 #

While the P2406 code can appear on any OBD-II equipped vehicle, it is more frequently reported in certain makes and models, especially those using a dedicated leak detection pump instead of a vent valve or pressure sensor. Vehicles commonly affected include:

• Chrysler, Dodge, Jeep (2005–2018 models)
• BMW (with LDP-equipped EVAP systems)
• Volkswagen, Audi
• Toyota, Lexus
• Ford, Lincoln, Mercury (select models)
• General Motors (Chevrolet, GMC, Cadillac, Buick)

Common Mistakes & Best Practices for P2406 #

A hasty or incomplete diagnosis can lead to wasted time and money. Here are frequent pitfalls and recommended practices when dealing with P2406:

• Replacing the leak detection pump without checking wiring or connections first
• Overlooking simple issues like corroded or loose connectors
• Not consulting OEM wiring diagrams for proper circuit testing
• Failing to clear codes and verify the repair with a proper drive cycle
• Best practice: Always begin with a thorough visual and electrical inspection before replacing parts

Quick FAQ on Code P2406 #

It’s normal to have questions when faced with a trouble code. Here are fast answers to the most common concerns:

• Q: Will P2406 cause my vehicle to fail inspection?
  A: Yes, in many states, the check engine light and an active EVAP code will result in a failed emissions inspection.
• Q: Can a loose gas cap trigger P2406?

A: No, P2406 specifically relates to the leak detection pump sense circuit, not the general EVAP leak codes caused by a loose gas cap.

• Q: Does this code mean my car is unsafe to drive?

A: Generally, no. While emissions may increase, vehicle safety and performance are rarely affected. Still, it’s best to repair it soon.