Understanding the P1495 Mitsubishi Diagnostic Trouble Code
When your Mitsubishi’s check engine light illuminates and a scan tool reveals the generic OBD-II code P1495, you are dealing with a specific fault within the Exhaust Gas Recirculation (EGR) system. In Mitsubishi vehicles, P1495 is defined as “EGR Valve Position Sensor Circuit Malfunction.” This code indicates that the Engine Control Module (ECM) has detected an abnormal voltage signal, an open circuit, or a short circuit in the feedback loop from the EGR valve position sensor. Unlike codes pointing to flow problems, P1495 is primarily an electrical or sensor-based fault, requiring a systematic diagnostic approach focused on wiring, connectors, and the sensor itself.
The Critical Role of the EGR Valve and Its Position Sensor
The EGR system is a cornerstone of modern emission control. It recirculates a metered amount of inert exhaust gas back into the engine’s intake manifold. This process lowers peak combustion temperatures, dramatically reducing the formation of harmful nitrogen oxides (NOx). The EGR valve position sensor is integral to this precision. It is typically a potentiometer attached to the valve shaft, providing real-time feedback to the ECM on the valve’s exact pintle position—whether fully closed, partially open, or fully open. This closed-loop feedback allows the ECM to accurately control EGR flow, ensuring optimal engine performance and emissions compliance.
How the Mitsubishi ECM Triggers Code P1495
The Mitsubishi ECM continuously monitors the voltage signal from the EGR valve position sensor. This signal should vary smoothly and predictably in relation to commanded valve position. Code P1495 is set when the ECM detects one of several fault conditions:
- Voltage Out of Range: The sensor signal is stuck too high (near reference voltage, 5V) or too low (near ground, 0V), indicating an open or short.
- Implausible Signal: The reported valve position does not logically match the engine’s operating conditions (e.g., sensor indicates “open” at idle when it should be closed).
- Signal Correlation Fault: A mismatch between the commanded position (duty cycle sent to the EGR valve actuator) and the actual position reported by the sensor.
When such a discrepancy persists over one or more drive cycles, the ECM logs P1495, illuminates the check engine light, and may disable the EGR system entirely, often resulting in noticeable driveability issues.
Common Symptoms and Causes of P1495 in Mitsubishi Models
Recognizing the symptoms of a P1495 fault is the first step in diagnosis. Drivers may experience one or more of the following issues, commonly reported in models like the Lancer, Outlander, Eclipse, and Galant.
Primary Symptoms of a P1495 Fault
- Illuminated Check Engine Light (MIL): The most immediate and obvious sign.
- Rough Idle or Stalling: Incorrect EGR flow due to faulty position data can cause unstable idle or even stalling, especially when cold.
- Engine Knocking or Pinging (Detonation): With the EGR system disabled, combustion temperatures rise, leading to audible knocking under acceleration.
- Reduced Fuel Economy: The ECM may enter a rich-fueling “limp” mode to protect the engine from knock, decreasing miles per gallon.
- Failed Emissions Test: With the EGR system inoperative, NOx emissions will be elevated, causing a test failure.
Root Causes of the P1495 Code
The causes of P1495 can be categorized into electrical, mechanical, and control unit failures.
- Electrical Faults:
- Damaged, frayed, or corroded wiring in the EGR valve position sensor circuit.
- Poor electrical connections at the sensor or ECM connectors.
- A failed EGR valve position sensor (internal potentiometer wear or failure).
- Mechanical Issues:
- A mechanically stuck or binding EGR valve due to heavy carbon deposits. The valve cannot move, so the sensor signal becomes static.
- Physical damage to the valve or sensor linkage.
- Other Potential Causes:
- A faulty EGR valve assembly (integrated actuator and sensor).
- In rare cases, a problem with the ECM itself, though this is less common.
Step-by-Step Diagnostic and Repair Procedure
Diagnosing P1495 requires a methodical approach, starting with the simplest checks. You will need a quality OBD2 scanner with live data capability, a digital multimeter (DMM), and basic hand tools.
Step 1: Preliminary Inspection and Live Data Analysis
Begin with a thorough visual inspection. Check the EGR valve, sensor, and all associated wiring for obvious damage, corrosion, or disconnected plugs. Next, use your scan tool to monitor live data. Look for the EGR valve position parameter (often listed as “EGR Pos,” “EGR Duty,” or “EGR Sensor Voltage”).
- With the engine off, key on, the reading should typically show 0% or a low voltage, indicating a closed valve.
- At a steady 2500 RPM, the value should increase, showing the valve opening. If the value is stuck at 0%, 100%, or 5V/0V and does not change, it confirms a circuit or sensor fault.
Step 2: Electrical Circuit Testing with a Multimeter
Disconnect the electrical connector from the EGR valve/sensor. Consult a vehicle-specific wiring diagram to identify the pins for sensor ground (≈ 0.5V), reference voltage (5V from ECM), and signal return.
- With the key on, engine off, probe the harness connector. You should find a stable 5V reference and a good ground.
- If reference voltage or ground is missing, trace the circuit back for opens or shorts.
- If power and ground are present, measure the resistance of the position sensor across its terminals (valve disconnected). Slowly move the valve pintle by hand. The resistance should change smoothly without any gaps or spikes. An erratic or open reading indicates a bad sensor.
Step 3: Mechanical and Final Component Checks
If the electrical tests pass, the valve itself may be mechanically bound. Remove the EGR valve (intake manifold side) and inspect the pintle and seat for heavy carbon buildup. The valve should move freely without binding. Clean the valve and passages thoroughly with a dedicated EGR/carburetor cleaner. Never force the valve open or closed. Reinstall and retest. If the valve is clean and moves freely but the code returns, and all electrical tests are good, the EGR valve assembly (with integrated sensor) is likely faulty and requires replacement.
Clearing the Code and Final Verification
After completing the repair, clear the DTC with your scan tool. Perform a test drive that includes various engine loads and RPMs to allow the ECM to complete its monitor cycles. Verify that the check engine light remains off and that live data from the EGR position sensor now responds correctly to driving conditions. This confirms a successful repair.
Conclusion: Addressing P1495 for Optimal Performance
Code P1495 on your Mitsubishi is a clear call to action for the vehicle’s emission control system. While it can lead to driveability concerns, its diagnosis is straightforward with the right tools and a logical process. By focusing on the electrical integrity of the position sensor circuit and the mechanical freedom of the EGR valve itself, most instances of P1495 can be resolved effectively. Addressing this code promptly restores engine efficiency, performance, and ensures your Mitsubishi meets its designed emission standards, keeping it running cleanly and reliably for the long term.