Lincoln P1402 Trouble Code: Complete Diagnostic and Repair Guide
The check engine light illuminating on your Lincoln’s dashboard is always a cause for concern. When a diagnostic scan reveals the trouble code P1402, it specifically indicates a problem with the Exhaust Gas Recirculation (EGR) system. This code means the Powertrain Control Module (PCM) has detected abnormal voltage or an irregular signal from the EGR gas differential pressure sensor, also known as the DPFE (Differential Pressure Feedback EGR) sensor. Understanding the causes, symptoms, and solutions for the Lincoln P1402 code is essential for restoring your vehicle to optimal running condition.
What is the P1402 Code on a Lincoln?
The P1402 code is a generic OBD-II code that means “EGR Metering Orifice – Circuit Low.” Although the description may vary slightly depending on your Lincoln’s model and year (Town Car, Navigator, MKZ, etc.), the core issue remains the same. The EGR system’s function is to reduce nitrogen oxide (NOx) emissions by reintroducing a small amount of exhaust gas into the intake manifold. The DPFE sensor measures the gas pressure before and after a calibrated orifice in the EGR tube. If the PCM receives a signal outside the expected range (typically a signal that is too low), it records the Lincoln P1402 code and illuminates the malfunction indicator lamp.
Symptoms of the P1402 Fault
It is crucial to recognize the signs that often accompany this code. Do not ignore them, as they can affect performance and fuel consumption.
- Rough or erratic idle: The engine may stall at idle or experience RPM fluctuations.
- Loss of power: A feeling of sluggishness during acceleration, especially under load.
- Knocking or pinging: A knocking noise from the engine during acceleration, caused by excessively high combustion temperatures.
- Increased fuel consumption: The engine runs less efficiently.
- Failed emissions test: Excessive emissions, particularly NOx.
Main Causes of the P1402 Code on Lincoln
Several components can be the source of this fault. A methodical diagnostic approach helps avoid replacing parts unnecessarily.
- A faulty DPFE sensor: This is the most common cause of the Lincoln P1402 code. The sensor itself is defective and sends an incorrect signal.
- Electrical circuit problems: Broken, corroded wires, or oxidized connectors between the DPFE sensor and the PCM can mimic a failure.
- Clogged or leaking DPFE hoses: The small rubber hoses connecting the sensor to the EGR tube can become clogged with carbon deposits or crack over time, distorting the pressure measurement.
- Problem with the EGR valve: Although the code points to the sensor circuit, a faulty or clogged EGR valve can be an underlying issue.
- PCM failure: Very rare, but a faulty engine control module could be the cause.
Diagnosis and Solutions for Fixing P1402
Before replacing anything, follow these steps for an accurate diagnosis.
1. Visual Inspection
Start with a thorough visual inspection. Locate the DPFE sensor (often mounted on top of the engine or near the EGR valve) and inspect the two small rubber hoses. Check that they are intact, properly connected, and not clogged. Examine the sensor’s electrical connector for any signs of corrosion or damage.
2. Testing the DPFE Hoses
Carefully disconnect the hoses from the sensor and blow through them to ensure they are not blocked. Use carburetor cleaner if necessary to clear them. Replace them if they are cracked or hardened.
3. Electrical Testing of the DPFE Sensor
Using a multimeter, you can check the reference voltage (usually 5V) and the ground at the connector. With the ignition on, also measure the sensor’s return signal. An abnormally low value (close to 0V) will confirm the diagnosis of the Lincoln P1402 code.
4. Cleaning or Replacing the EGR Valve
If the sensor and its hoses are in good condition, it is safe to check the state of the EGR valve. Remove it and inspect it for excessive carbon buildup that could prevent it from functioning correctly. A thorough cleaning can sometimes resolve the problem.
5. Replacing the DPFE Sensor
If all other causes are ruled out, replacing the DPFE sensor is the most likely solution. This part is relatively affordable and its replacement is straightforward once located. After replacement, clear the code with an OBD2 scanner and perform a road test to confirm the repair.
Conclusion
The Lincoln P1402 trouble code, while concerning, is often a problem that can be resolved cost-effectively with proper diagnosis. By focusing first on the DPFE sensor and its small hoses, you have a high chance of quickly identifying and correcting the fault, thereby restoring the performance and efficiency of your luxury vehicle. For complex work, do not hesitate to consult a certified mechanic.