P0404Generic code

P0404 Code: Exhaust Gas Recirculation Control Circuit Range/Performance

The P0404 code means the EGR valve is not moving the way the computer commands, so its real position does not match the desired one. Carbon is the most common cause. It often shows up with a rough idle or pinging under load.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$50 to $500
Difficulty
Medium
System
Emissions Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0404 code means

On electronic EGR valves, the computer commands a position and checks it with the sensor built into the valve. If the difference between the two stays, it stores the P0404 code.

Usually the valve is moving with difficulty because of carbon, or its motor is worn. A position sensor that no longer reads correctly can also be the reason.

It often appears together with P0401 or P0402, and sometimes with an unstable idle.

The gap between the commanded and the real position usually grows little by little as carbon builds up. At first the code appears only on a cold engine or after short trips, and later it becomes constant. That is why vehicles that mostly do city driving should have the EGR cleaned as preventive maintenance every so many miles. After cleaning or replacing the valve, some manufacturers require an EGR position learn procedure with a scan tool.

P0404 code symptoms

  • Unstable idle.
  • Pinging under load.
  • Check engine light on.

Likely causes of the P0404 code

  1. Carbon in the valve. It slows the movement and creates a difference between commanded and real position.
  2. Worn valve motor. It does not reach the commanded position quickly enough.
  3. Position sensor built into the valve giving a wrong reading.
  4. Corroded connector. It adds resistance.

How to diagnose the P0404 code step by step

  1. Compare desired and real position on the scan tool.
  2. Command the valve and watch whether it moves smoothly.
  3. Remove the valve and clean it.
  4. Measure the position sensor.
  5. Run the EGR learn procedure after cleaning or replacing it, if the manufacturer requires it.

How to fix the P0404 code

  • Clean the valve.
  • Replace the EGR valve if the motor or the sensor is failing.
  • Clear the code and verify the repair.

Technical reference data

  • Position sensor: 0.3 to 0.9 volts closed and 4.0 to 4.5 volts open.
  • These are approximate values, so check the manufacturer data for your engine.

Brand-specific notes

P0404 on GM

Very common on GM vehicles with the electric EGR valves of the 2000s, and also on diesel engines.

Frequently asked questions about P0404

Can I drive with a P0404 code?
Yes, with caution. Watch for a rough idle and pinging under load.
Does cleaning fix it?
Many times it does, because carbon is the most common cause. If the motor or the sensor is worn, the valve has to be replaced.
What happens if I do not repair it?
You get higher emissions and possible pinging. The valve will also keep struggling as the carbon builds up.
How much does it cost to fix P0404?
Between $50 and $500, depending on whether the valve only needs cleaning or has to be replaced. Diagnosing the P0404 code properly first keeps you from paying for parts you do not need.
What does the P0404 code mean?
It is a generic OBD2 code for a range or performance problem in the EGR control circuit. The valve position does not match what the computer commanded.
What is the most common cause of P0404?
Carbon in the EGR valve, which slows its movement. A worn valve motor or a bad position sensor comes next.

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