What does the p1404 code mean on a 2001 Chevy silverado?

P1404 on a 2001 Chevy Silverado indicates a problem with the EGR (Exhaust Gas Recirculation) system's position sensor. Specifically, it means the PCM (Powertrain Control Module) is detecting a malfunction in the EGR position sensor circuit. This sensor tells the PCM how much EGR gas is being recirculated. A faulty sensor means the PCM can't accurately control the amount of exhaust gas being sent back into the engine.

This could be caused by several things:

* Faulty EGR Position Sensor: The sensor itself might be malfunctioning due to wear and tear, corrosion, or damage. This is the most likely culprit.

* Wiring issues: A broken, shorted, or corroded wire in the sensor circuit can cause this code.

* Faulty EGR valve: While the code points to the sensor, a sticky or malfunctioning EGR valve can indirectly cause the sensor to report incorrectly.

* Vacuum leaks: Leaks in the vacuum lines that control the EGR valve can also affect the sensor reading.

To properly diagnose and repair this, a mechanic should:

1. Check the EGR position sensor itself: This might involve testing the sensor's voltage and resistance readings using a multimeter.

2. Inspect the wiring harness: Look for any broken, frayed, or corroded wires leading to the sensor.

3. Test the EGR valve: Ensure the valve is opening and closing properly.

4. Check for vacuum leaks: Inspect all vacuum lines associated with the EGR system.

Simply replacing the EGR position sensor might fix the problem, but a thorough inspection is recommended to pinpoint the root cause and prevent future issues. Ignoring the problem could lead to poor engine performance, increased emissions, and potential damage to the engine.