Understanding the Subaru P1495 Diagnostic Trouble Code
The illumination of the check engine light in your Subaru, accompanied by the retrieval of diagnostic trouble code P1495, signals a specific issue within the vehicle’s Evaporative Emission Control (EVAP) system. Unlike generic codes, P1495 is often manufacturer-specific, and in the context of Subaru vehicles, it is formally defined as “Leak Detection Pump Circuit Malfunction.” This code indicates that the vehicle’s Engine Control Module (ECM) has detected an electrical or functional problem with the Leak Detection Pump (LDP), a critical component responsible for monitoring the fuel vapor system for leaks. Ignoring this code can lead to failed emissions tests, reduced fuel efficiency, and potentially allow harmful hydrocarbons to escape into the atmosphere.
What is the EVAP System and the Leak Detection Pump’s Role?
The EVAP system is designed to capture and store fuel vapors from the fuel tank, preventing them from being released into the air. These vapors are later purged and burned in the engine during normal operation. The Leak Detection Pump (LDP) is the system’s self-diagnostic tool. It doesn’t pump fuel; instead, it creates a vacuum or pressure within the sealed EVAP system. The ECM then monitors the system’s ability to hold this vacuum/pressure. If the pressure decays too quickly, it indicates a leak, triggering a different code (like a P0442 “small leak”). Code P1495, however, means the ECM cannot properly command or monitor the LDP itself.
Technical Definition of Code P1495
Technically, P1495 is set when the ECM detects an unexpected voltage reading or circuit response from the Leak Detection Pump. This could be:
- An open circuit (broken wire).
- A short circuit to power or ground.
- A faulty LDP motor or internal solenoid.
- A problem with the LDP’s internal pressure switch.
The ECM performs this check during key-on and during specific drive cycles, making it a “hard” electrical fault rather than an intermittent leak detection.
Symptoms and Causes of a P1495 Code in Your Subaru
While sometimes the P1495 code may be present without noticeable drivability issues, certain symptoms often accompany it. Recognizing these signs can help correlate the code with a tangible vehicle behavior.
Common Symptoms of a P1495 Fault
- Illuminated Check Engine Light (MIL): The primary and most common indicator.
- Failed Emissions Inspection: The vehicle will not pass a state or local emissions test with an active EVAP system code.
- Possible Fuel Odor: While not always present, a compromised EVAP system can sometimes lead to a smell of gasoline near the vehicle.
- No Other Drivability Issues: The engine typically runs normally, as this is an emission control fault, not a fuel delivery or ignition fault.
Primary Causes of the P1495 Code
The root cause of P1495 is always related to the Leak Detection Pump circuit. Diagnosis should follow a logical progression from simple to complex.
- Faulty Leak Detection Pump (LDP): The most common culprit. The internal electric motor, solenoid, or pressure switch can fail.
- Damaged Wiring or Connectors: Corroded, broken, or frayed wires in the harness connecting the LDP to the ECM. Pay close attention to the connector at the LDP itself.
- Poor Electrical Ground: The LDP requires a clean, solid ground. A corroded or loose ground point can cause circuit malfunctions.
- Blown Fuse: A dedicated fuse in the engine bay fuse box often powers the LDP circuit.
- Rare: Faulty Engine Control Module (ECM): This is exceedingly rare and should only be considered after all other components and wiring have been thoroughly tested.
Step-by-Step Diagnosis and Repair for Subaru P1495
Proper diagnosis requires a basic multimeter and, ideally, a scan tool capable of activating the LDP for a functional test. Always begin by verifying the code, checking for technical service bulletins (TSBs) for your specific Subaru model and year, and performing a thorough visual inspection.
Step 1: Preliminary Checks and Visual Inspection
Locate the Leak Detection Pump. In most Subaru models (Impreza, Outback, Forester, Legacy), it is a black, cylindrical component mounted near the fuel tank or in the rear quarter panel area. Visually inspect:
- The LDP electrical connector for corrosion, bent pins, or looseness.
- The wiring harness for obvious damage, chafing, or rodent chewing.
- The vacuum hoses connected to the LDP and EVAP canister for cracks, disconnections, or brittleness.
- The relevant fuse in the under-hood fuse box (consult your owner’s manual).
Step 2: Electrical Circuit Testing with a Multimeter
With the connector disconnected from the LDP, use a multimeter to check:
- Power Supply: With the ignition ON, check for battery voltage (typically 12V) at the designated power pin in the harness connector.
- Ground Circuit: Check for continuity between the ground pin in the harness connector and a known good chassis ground. Resistance should be very low (less than 5 ohms).
- ECM Signal Line: This requires a wiring diagram. Check for continuity on the signal wire back to the ECM connector and check for shorts to power or ground.
If power and ground are correct, the fault likely lies with the LDP itself.
Step 3: Testing the Leak Detection Pump Itself
You can perform a basic bench test. Apply battery voltage and ground directly to the LDP’s motor terminals (using fused jumper wires). A functioning pump will make a distinct clicking or humming sound as it operates. If it does not activate, the pump is faulty. Some advanced scan tools can command the LDP “on” and “off” for a functional test while installed.
Step 4: Repair and Clearing the Code
Based on your findings:
- Replace the LDP: If the pump fails the bench test. Use a high-quality OEM or reputable aftermarket part.
- Repair Wiring: Solder and seal any broken wires. Replace damaged connectors.
- Clean Ground Points: Disconnect, clean with a wire brush, and securely reconnect the ground connection.
After repairs, clear the P1495 code with your scan tool. The ECM will need to complete a full drive cycle to verify the fix. Monitor for the code’s return over the next several days of driving.
Preventative Maintenance and Final Thoughts
While the LDP is not a routine maintenance item, keeping the EVAP system healthy can prevent related issues. Avoid over-tightening the gas cap, which can damage the seal. During undercarriage washes or in snowy regions where salt is used, be mindful of the LDP’s location, as corrosion is a key enemy of electrical components. Addressing a P1495 code promptly not only ensures your Subaru passes emissions tests but also contributes to a cleaner environment by ensuring the EVAP system operates as engineered. For complex electrical diagnosis, consulting a professional Subaru technician with proper diagnostic equipment is always a recommended course of action.