P0404🌫 Emissions / EGRDrive with caution, fix soon

P0404: EGR Circuit Range/Performance (Meaning, Causes, Fixes)

Reviewed 2026-10-23 · Based on 2 cited source(s)

What P0404 means

The EGR system feeds a small, metered amount of exhaust back into the cylinders. Because exhaust is inert, it lowers combustion temperature and cuts oxides of nitrogen (NOx). RepairPal says it is usually no more than 10 percent of the intake air and keeps peak combustion temperature below about 2500 F. OBD-Codes.com says a vehicle with P0404 likely has an electrically controlled EGR valve with a built-in feedback sensor that tells the powertrain control module (PCM) how far the valve is open. The code sets if the PCM wants the valve open but the feedback shows it closed, or wants it closed but the feedback shows it open. RepairPal defines it as the EGR valve position sensor reading above or below its specified range, and also says the PCM sets it when it doesn't detect the EGR flow it requested. The code can set during normal driving or during the EGR monitor tests, which RepairPal says usually run during steady freeway and steady city driving. It is a generic OBD-II code, though repair steps vary by make and model. The sources differ in a few ways. The names differ slightly (OBD-Codes.com: Exhaust Gas Recirculation "A" Circuit Range/Performance; RepairPal: Exhaust Gas Recirculation "A" Control Circuit Range/Performance). OBD-Codes.com focuses on an electric valve and its 5 volt reference, ground and control circuits, while RepairPal also lists vacuum-side causes (lack of vacuum to the valve, a bad vacuum supply solenoid) and feedback from the MAP, DPFE and EGR temperature sensors. For symptoms, OBD-Codes.com describes a valve stuck open causing rough or no idle, while RepairPal describes pinging under load or at higher speeds from too little EGR flow. RepairPal rates it Moderate; OBD-Codes.com gives no rating.

Severity: can I keep driving?

Drive with caution, fix soon

Get it diagnosed within a reasonable time. RepairPal rates P0404 Moderate, meaning it may not threaten safety or drivability right away. OBD-Codes.com gives no severity rating and says there may be no symptoms beyond the check engine light, but if carbon holds the EGR valve open the engine may idle rough or not idle at all. If the engine stalls or pings badly under load, get it checked sooner.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Carbon buildup on the EGR valve or in the EGR passages (both sources; OBD-Codes.com says this or a bad valve is the usual cause)
  2. Faulty EGR valve (both sources)
  3. Faulty EGR valve position sensor, or its connector or wiring (RepairPal)
  4. Open or short in the EGR 5 volt reference, ground or PCM-controlled voltage circuit (OBD-Codes.com)
  5. Lack of proper vacuum or electrical signal to the EGR valve, or a bad EGR vacuum supply solenoid (RepairPal only)
  6. Bad feedback from the MAP, DPFE or EGR temperature sensor (RepairPal only)
  7. Faulty PCM (OBD-Codes.com, less likely)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Record the freeze frame data so you know the conditions when the code set, and try to repeat them with a data-streaming scan tool connected (RepairPal).
  2. With a scan tool, command the EGR valve open and compare actual EGR position with desired position (OBD-Codes.com). If they match closely, the fault is likely intermittent, such as a piece of carbon that has since come loose or a valve winding that fails as it heats up.
  3. If actual and desired don't match, unplug the EGR sensor and check for a 5 volt reference at the connector, then check for a good ground with the EGR commanded on (OBD-Codes.com). Repair any open or short you find.
  4. If reference and ground are good, check the control circuit voltage. OBD-Codes.com says it should rise as the valve opens further; if it does, the EGR valve is the likely fault, and if it doesn't, repair the control circuit.
  5. RepairPal suggests checking the valve position sensor's accuracy by raising and lowering the valve, checking that the valve gets its specified vacuum on vacuum systems, and a flow test: at 3000 RPM, opening the valve fully should drop manifold vacuum by at least 3 inches of mercury. If it doesn't, the passages may be restricted or plugged.
  6. Don't assume it's the valve. RepairPal says P0404 is often not a problem with the EGR valve itself.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The engine stalls, idles very roughly or pings badly
  • You don't have a scan tool that can command the EGR valve and show desired and actual position
  • The code returns after cleaning or replacing the EGR valve
  • There are misfire codes along with P0404
  • You need to pass an emissions inspection soon

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0404?

Usually yes for a short time, if the engine runs normally. RepairPal rates it Moderate and OBD-Codes.com says there may be no symptoms beyond the check engine light. Get it diagnosed reasonably soon, and sooner if the engine idles rough, stalls or pings.

Is P0404 a bad EGR valve?

Sometimes. OBD-Codes.com says the code usually points to carbon buildup or a bad EGR valve, but RepairPal says it is often not the valve itself and can be the EGR valve position sensor, wiring, vacuum control or other feedback sensors. Test before buying parts.

What's the difference between P0404 and P0401 or P0402?

P0401 means too little EGR flow and P0402 means too much. P0404 means the EGR valve's position or circuit reading doesn't match what the computer commanded or is out of its expected range.

How much does it cost to fix P0404?

Neither source gives a repair cost for P0404. It can be carbon cleaning, a sensor, wiring or the valve, so diagnose it first.

Sources

  1. OBD-Codes.com: P0404 Exhaust Gas Recirculation Circuit Range/Performance
  2. RepairPal: P0404 Exhaust Gas Recirculation "A" Control Circuit Range/Performance (rated Moderate)

Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.