# P0404: Exhaust Gas Recirculation "A" Control Circuit Range/Performance **Verdict:** Drive to a shop this week Emissions - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $150-$750 - **Urgency:** This week - **Most likely:** Carbon-stuck EGR valve - **DIY?:** Cleaning sometimes; test first ## Quick answer P0404 means the EGR valve is not moving to the position the engine computer commands. The computer compares where it told the valve to go with where the valve's position sensor says it actually is. Carbon buildup that makes the valve stick is the most common cause, followed by a failed valve or its built-in sensor. ## What does P0404 mean? The exhaust gas recirculation (EGR) valve lets a small, metered amount of exhaust back into the intake to lower combustion temperatures and cut nitrogen oxide (NOx) emissions. On many engines the valve is opened electrically, by a motor or solenoid, and a position sensor on the valve reports how far it actually opened. That lets the computer fine-tune EGR flow at cruise and keep the valve closed at idle and full throttle. P0404 is a range/performance code. The control circuit has power and is not shorted, but the valve's measured position does not follow the commanded position closely enough. A valve that sticks partly open, moves too slowly, or does not open at all can set it, as can a position sensor reporting the wrong value. The "A" means the first or only EGR system. Many makers need the fault on two drive cycles before the light comes on, and some engines run well despite it. ## What are the symptoms of P0404? - Check engine light on - Rough idle or stalling at stops if the valve sticks open - Hesitation or stumbling on light acceleration - Pinging under load if the valve stays closed - Failed emissions test from high NOx on tailpipe-tested cars ## What causes P0404? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Carbon buildup sticking the EGR valve** (most common). Exhaust carries soot and oil residue that slowly bakes onto the valve pintle and seat. Over time the valve moves sluggishly, sticks partly open, or cannot close fully, so its position lags the command. This is most common on higher-mileage engines, engines that burn oil, and cars driven mostly on short trips. Removing the valve usually shows heavy deposits. 2. **Failed EGR valve or built-in position sensor** (common). On many electronic EGR valves, the motor and the position sensor are built into one unit. A worn motor may not move the valve fully, and a worn sensor track can report the wrong position even when the valve moves correctly. Either way the unit is usually replaced as a whole, since the parts are rarely sold separately. 3. **Intermittent wiring or connector problem** (less common). The EGR valve sits near the exhaust or intake, where heat makes connectors brittle and wires crack. A poor connection on the control, reference or signal wire can make the reported position jump around, which the computer treats as a range/performance fault. Wiggle-testing the harness while watching position on a scan tool can reveal it. 4. **Vacuum supply problem on vacuum-operated valves** (less common). Some engines open the EGR valve with engine vacuum through a control solenoid, while a sensor on the valve reports position. A cracked hose, failed solenoid or blocked vacuum port keeps the valve from opening as commanded. This applies mainly to older vehicles; check hoses for splits and confirm vacuum reaches the valve when EGR is commanded. ## How do you diagnose P0404? 1. Read all codes and freeze-frame data, noting related EGR codes such as P0401, P0405 or P0406. 2. With a scan tool, command the EGR valve open and closed and compare desired and actual position. 3. Check the valve's power, ground, reference and signal wiring for damage or poor connections. 4. Remove and inspect the valve for carbon buildup and binding, and check the passages it feeds. 5. Check for software updates or service bulletins that address P0404 on your engine. ## How do you fix P0404, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Clean EGR valve and passages | $150-$450 | Works when carbon is the cause and the valve and sensor test good. | | Replace EGR valve with integrated sensor | $250-$750 | Diesel and some newer gas engines can cost more. | | Repair EGR wiring or vacuum supply | $100-$300 | Fixes damaged wiring, a cracked hose or a failed vacuum solenoid. | Full price breakdowns: [egr valve replacement cost](/cost/egr-valve-replacement). ## Is it safe to drive with P0404? > **Drive to a shop this week.** Usually safe to drive for a short time if the engine runs normally. If it idles very rough, stalls at stops or pings under load, get it fixed soon, since a stuck-open valve can stall the engine in traffic. ## Will P0404 fail an emissions test? P0404 with the check engine light on fails an OBD-based emissions test in most states, and the EGR monitor will not show ready until the valve passes its test. In areas that also measure tailpipe gases, a stuck-closed valve can raise NOx readings. Clear the code only after the repair, then complete a drive cycle. ## After the repair: clearing P0404 Clear the code, then drive with steady cruising and some gentle decelerations once the engine is fully warm, since many EGR tests run in those conditions. A scan tool should show actual EGR position following desired position closely. The fix worked when the EGR monitor reports complete and no pending code returns. ## How to prevent P0404 - Drive at steady highway speeds now and then so carbon does not build up as quickly. - Fix oil burning and leaking valve guides or PCV problems that coat the EGR valve with residue. - Change oil on schedule with the grade your owner's manual specifies. - Address EGR codes early, before heavy carbon also clogs the intake passages. ## Codes often seen with P0404 - [P0400](/codes/p0400): Exhaust Gas Recirculation "A" Flow - [P0401](/codes/p0401): Exhaust Gas Recirculation "A" Flow Insufficient Detected - [P0403](/codes/p0403): Exhaust Gas Recirculation "A" Control Circuit - [P0405](/codes/p0405): Exhaust Gas Recirculation Sensor "A" Circuit Low - [P0406](/codes/p0406): Exhaust Gas Recirculation Sensor "A" Circuit High ## Frequently asked questions ### Can I drive with a P0404 code? Usually yes for a short time if the engine runs normally. If the valve is stuck open, you may get rough idle or stalling at stops, which is unsafe in traffic. If it is stuck closed, the engine may ping under load. Get it diagnosed soon in either case. ### What does EGR control circuit range/performance mean? It means the EGR valve's actual position, reported by its position sensor, is not matching the position the computer commanded. The circuit itself is intact, but the valve is sticking, moving slowly, or its sensor is reading wrong. Carbon buildup is the most frequent reason. ### How much does it cost to fix P0404? Most P0404 repairs cost $150 to $750 at an independent shop. Cleaning the valve and passages runs about $150 to $450, and a new electronic EGR valve $250 to $750. Wiring or vacuum repairs cost about $100 to $300. Diesel EGR valves often cost more. ### Can cleaning the EGR valve fix P0404? Yes, if carbon is making the valve stick and its motor and sensor still work. Cleaning the pintle, seat and passages often restores normal movement. If the code returns soon after cleaning, or the valve still lags on a scan tool test, the valve or its sensor has likely failed. ### Can I replace the EGR valve myself? Often yes on engines where the valve is bolted on top or on the side and easy to reach. Use a new gasket, torque the bolts to specification, and clear the code. Some engines need a scan tool relearn for the valve position, so check service information before starting. ### What is the difference between P0403 and P0404? P0403 is an electrical fault in the EGR control circuit, such as an open or short. P0404 means the circuit works but the valve is not reaching its commanded position. P0403 usually points to wiring or a dead coil, while P0404 more often points to a sticking valve. ### Can a stuck EGR valve cause stalling? Yes, a valve stuck partly open lets exhaust into the intake at idle, when the engine needs fresh air most. That causes rough idle and can stall the engine at stops or when slowing down. If stalling has started, have the valve checked before relying on the car in traffic. ### Will P0404 hurt my engine? It rarely causes direct damage in the short term. A valve stuck closed raises combustion temperatures, which can cause pinging and, over a long time, extra wear. A valve stuck open mostly causes drivability problems. Repairing it promptly also prevents carbon from spreading further into the intake. ### Do I need a relearn after replacing the EGR valve? Some vehicles need the computer to learn the new valve's closed position, either automatically after a key cycle or with a scan tool. Others need nothing. Check service information or ask the shop, because skipping a required relearn can bring P0404 straight back. ### Will P0404 pass inspection? No, P0404 with the check engine light on fails an OBD-based emissions test in most states. The EGR monitor also stays not ready until the valve passes its self-test. Fix the cause, clear the code, and drive with steady cruising until the monitor completes before testing. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) ## Other emissions codes - [P0400 Exhaust Gas Recirculation "A" Flow](https://diagxcar.com/codes/p0400) - [P0401 Exhaust Gas Recirculation "A" Flow Insufficient Detected](https://diagxcar.com/codes/p0401) - [P0402 Exhaust Gas Recirculation "A" Flow Excessive Detected](https://diagxcar.com/codes/p0402) - [P0403 Exhaust Gas Recirculation "A" Control Circuit](https://diagxcar.com/codes/p0403) - [P0405 Exhaust Gas Recirculation Sensor "A" Circuit Low](https://diagxcar.com/codes/p0405) - [P0406 Exhaust Gas Recirculation Sensor "A" Circuit High](https://diagxcar.com/codes/p0406) - [P0410 Secondary Air Injection System "A"](https://diagxcar.com/codes/p0410) - [P0411 Secondary Air Injection System "A" Incorrect Flow Detected](https://diagxcar.com/codes/p0411) - [P0420 Catalyst System Efficiency Below Threshold (Bank 1)](https://diagxcar.com/codes/p0420) - [P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)](https://diagxcar.com/codes/p0421) ## Symptoms - [Why is my car idling rough?](https://diagxcar.com/symptoms/rough-idle) - [Why does my car stall while driving?](https://diagxcar.com/symptoms/car-stalls-while-driving) - [Why does my car hesitate when I accelerate?](https://diagxcar.com/symptoms/car-hesitates-when-accelerating) ## Repair costs - [EGR valve replacement cost](https://diagxcar.com/cost/egr-valve-replacement): $250-$850 --- Source page: https://diagxcar.com/codes/p0404 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.