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DTC codes / GM codes / P1404

P1404 · GMExhaust Gas Recirculation System Valve 2

P1404 on GM vehicles indicates that the powertrain control module has detected a fault with the exhaust gas recirculation (EGR) system, specifically the second EGR valve circuit or its control. The computer monitors the EGR valve position and electrical circuit, and when the actual position does not match the commanded position within a calibrated range, it sets this code. This typically results in the valve failing to open or close as commanded, which can affect emissions and driveability.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Rough idle or stalling, especially when the engine is cold or at low speeds.
  • Engine ping or knocking under light acceleration due to excessive combustion temperatures.
  • Reduced fuel economy as the engine management strategy compensates for the EGR fault.
  • Failed emissions test due to increased oxides of nitrogen (NOx) output.
  • In some cases, a surging or hesitation during light throttle application.

Common causes, most likely first

  1. Carbon buildup or debris obstructing the EGR valve pintle or passages, preventing proper movement.
  2. Faulty EGR valve position sensor or solenoid integrated into the valve assembly.
  3. Damaged or corroded electrical connector or wiring to the EGR valve.
  4. Failed EGR valve motor or actuator (on electronic EGR valves).
  5. Vacuum supply leak or faulty vacuum solenoid on vacuum-operated EGR systems.
  6. Exhaust backpressure issues or clogged EGR passages in the intake manifold.
  7. Rarely, a faulty powertrain control module (PCM) driver circuit.

How to diagnose and fix it

  1. Inspect the EGR valve electrical connector and wiring for corrosion, damage, or loose pins; repair as needed.
  2. Remove the EGR valve and check for carbon deposits; clean the valve and passages with appropriate solvent if clogged.
  3. Test the EGR valve operation using a scan tool to command the valve open and closed while monitoring position feedback.
  4. Check vacuum supply and solenoid operation on vacuum-controlled EGR systems using a vacuum gauge.
  5. Measure resistance of the EGR valve motor and sensor circuits and compare to manufacturer specifications.
  6. If the valve fails to respond or feedback is erratic, replace the EGR valve assembly.
  7. Clear the code and perform a drive cycle to verify the repair; recheck for pending codes.

Carbon Buildup Often Mimics a Failed EGR Valve

  • Many P1404 codes are resolved by cleaning the EGR valve and passages rather than replacing the valve, especially on higher-mileage GM engines.
  • A stuck-open EGR valve can cause a rough idle and stall, but a stuck-closed valve may produce no driveability symptoms at all, leading owners to ignore the light.
  • The EGR valve position sensor can fail independently of the valve mechanism, so a scan tool reading of the sensor voltage is essential before condemning the valve.
  • On some GM models, a weak battery or charging system can cause erratic EGR valve operation and set this code without a hard failure.
  • Exhaust leaks upstream of the EGR valve can affect backpressure and cause the valve to not flow as expected, triggering P1404 even when the valve itself is good.

Can I keep driving with P1404?

You can usually continue driving with P1404, but avoid heavy acceleration and long trips until diagnosed, as prolonged driving with a faulty EGR system can lead to increased emissions and potential engine knock. If the engine runs rough or stalls, have it checked promptly to prevent safety issues.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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