P0404 – Exhaust Gas Recirculation Circuit Range/Performance (Kia)

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By Reinier (Contact Me)
Last Updated 2024-02-26
Automobile Repair Shop Owner
CodeFault LocationProbable Cause
P0404 Exhaust Gas Recirculation Circuit Range/Performance
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Wiring, EGR valve, PCM

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Table of Contents

  1. What Does Code P0404 Mean?
  2. Where is the P0404 sensor located?
  3. What are the common causes of code P0404?
  4. How expensive is it to fix code P0404?
  5. What are the symptoms of code P0404?
  6. What are common solutions to code P0404?
  7. How serious is code P0404?
  8. How difficult is it to repair code P0404?
  9. Codes Related to P0404
  10. Get Help with P0404

What Does Code P0404 Mean?

OBD II fault code P0404 is a generic trouble code that is defined as, P0404 – “Exhaust Gas Recirculation Circuit Range/Performance”, and is set when the PCM (Powertrain Control Module) detects a defect, failure, or malfunction in the EGR system’s control or signal circuits. Note that the presence of code P0404 could have varying results, which include but are not limited to the setting related trouble codes, erratic operation of the EGR system, and an inability to clear or resolve related trouble codes that include P0403, P0406, and others that are listed at the end of this guide.

In all EGR-equipped engines, the purpose of the EGR system is to divert some exhaust gas away from the exhaust system and then introduce the diverted exhaust gas into the air intake system via a calibrated and computer-controlled valve, known as the EGR valve.

While it might seem counterproductive to feed largely incombustible exhaust into the cylinders, doing so reduces the high combustion temperatures that are a feature of modern internal combustion engines as a means of preventing the formation of NOx, a harmful and toxic combination of oxygen and nitrogen. As a practical matter, oxygen in the fuel and nitrogen in the intake air combine at combustion temperatures of about 2379 degrees F to form NOx, a generic name for a group of several toxic exhaust gases that are implicated in environmental degradation and many human health issues.

So, since combustion temperatures in many modern engines often exceed the temperature at which NOx forms, one common strategy to reduce combustion temperatures is to introduce small amounts of exhaust gas into the cylinders to reduce the efficiency of the combustion process under some engine operating conditions to reduce the combustion temperature to below the level at which NOX forms.

However, to make this system work effectively, the flow of exhaust gas into the cylinders must be-

  • metered exactly to prevent an over-dilution of the air/fuel mixture, and
  • introduced only when optimal combustion conditions are not critical for efficient engine operation, such as during steady high-speed cruising at highway speeds

In terms of operating principles, the PCM will monitor operating conditions continuously, and when the PCM deems the current operating conditions are likely to produce NOx in the cylinders, it will command the EGR valve open by a calculated amount to introduce only enough exhaust gas into the cylinders to prevent the formation of NOx. However, since the PCM cannot monitor or measure the rate of exhaust gas flowing through the EGR valve exactly, it uses the position of the EGR valve’s pintle to infer the volume of exhaust gas that flows through the valve.

In a fully functional EGR system, no exhaust gas will flow through the EGR valve when it is in the closed position but since the PCM cannot monitor the position of the valve pintle directly, it relies on a sensor whose function it is to monitor the status of the valve continuously. In practice, the position sensor is the only input data source the PCM uses to monitor the EGR valve’s status.

In practice, most EGR control systems work reasonably well but given the harsh conditions that EGR valves are subjected to, it is not surprising that the actual positions of their moveable parts often do not agree with the positions that a PCM expects to see under any given set of operating conditions. For instance, a PCM typically expects to see a fully closed EGR valve during idling or WOT (Wide Open Throttle) conditions, but a build-up of carbon inside the valve could prevent the valve from closing fully.

However, as with many other engine management systems, the control and signal circuits of modern EGR systems are subject to harsh conditions that include huge temperature fluctuations, near-constant vibration, and exposure to fuel and oil residues. Moreover, the PCM depends on receiving accurate input data from the EGR system to make the system work as expected, but since damage to wiring and electrical connectors typically often occurs slowly and over long periods, some types of wiring failures cannot be classified by the PCM.

In cases like these, the PCM will only note that a problem, defect, or malfunction is present in the EGR system, without being able to specify or identify the problem, as it would have done had the fault involved clearly identifiable issues like short circuits, open circuits, or a stuck EGR valve.

In such cases, the PCM will set code P0404 as an indication that either (or both) an electrical or mechanical fault is present in the EGR system. Note that depending on the a) nature of the problem, and b) the nature of additional codes the presence of code P0404 had precipitated, the PCM might also initiate a fail-safe or limp mode that will severely restrict the engine’s speed and power output until the fault that caused code P0404 to be set is found and corrected.

Where is the P0404 sensor located?

This image shows the type of damage to wiring (arrowed) that is very difficult to detect during a visual inspection. Nonetheless, this type of near impossible-to-detect damage to wiring is a common cause of trouble codes like not only P0404 but also other trouble codes that indicate electrical or mechanical control system issues in other engine and fuel management systems on modern vehicles.

In practice, the best way to find near-invisible damage to wiring is to have the affected or suspect wiring harness inspected and tested by professional persons using professional-level diagnostic and testing equipment.

What are the common causes of code P0404?

Although the most common causes of code P0404 are largely similar across all Kia applications, it is important to note the following-

  1. While part/component failures or malfunctions cannot be ruled out as possible causes of code P0404, electrical issues such as damaged wiring or bad electrical connections are far more likely to be the cause of code P0404 than parts failures
  2. Since the correct functioning of EGR systems on Kia (and most other Asian) vehicles depends on effective communication between the EGR valve and the PCM, even slightly abnormal electrical values anywhere in the EGR system can cause the system to operate outside of expected parameters- hence the term “performance” in the definition of code P0404
  3. As a general rule, the EGR systems on Asian vehicles demand the use of OEM or OEM-equivalent EGR valves and position sensors. Few, if any, non-OEM grade EGR valves comply with OEM calibration and performance standards, which means that it may sometimes be impossible to resolve code P0404 and other EGR codes on Asian vehicles until an unsuitable or substandard aftermarket EGR valve is replaced with an OEM or OEM-equivalent part
  4. Because there are slight manufacturing differences between even OEM EGR valves, no two OEM EGR valves will have the same operating characteristics. Therefore, all replacement EGR valves must be integrated into the vehicle’s engine management system using a relearn procedure that requires the use of at least a capable high-end scan tool with programming capability. Failing to perform this procedure could result in code P0404 (and others) persisting despite your best efforts to resolve the problem
  5. Take particular note of the fact that most smartphone-based code readers, as opposed to proper scan tool-based diagnostic software, are often unable to “de-code” fault code data/parameters stored in vehicles’ fault memories correctly. One result of this is the fact that it is sometimes impossible to clear fault codes effectively with such apps, and another is that (depending on the phone app used) the fault may be repeatedly triggered or reset in the vehicles’ fault memory
  6. Put differently, the above point means that the vehicle may sometimes not recognize the code readers’ attempt to clear the code(s), so it might seem that the fault reappears continually when in fact, a recent repair attempt might have been successful. The best course of action to avoid such a situation is to always use proper diagnostic equipment to extract and clear fault codes

Nonetheless, other possible causes of code P0404 could include one or more of the following-

  • Damaged, burnt, shorted, corroded, or disconnected wiring o electrical connectors anywhere in the EGR system’s control and signal circuits
  • Abnormal voltage electrical resistances in the (EGR valve) position sensor’s 5V reference circuit. In a fully functional system, this voltage changes as the EGR valve opens and closes, and so the position sensor will generate signal voltages that range from about 0.1 volts to about 4.5V to 4.9V. Therefore, if an open circuit exists in the reference voltage circuit between the PCM and the EGR valve, the signal voltage will be 0.0V. Similarly, if the signal voltage does not change at all, the EGR valve is likely stuck open or closed, which will typically set an EGR system performance code along with codes relating to exhaust gas flow issues through the EGR valve
  • Poor or bad ground connection in the EGR valve’s control circuit
  • Failed or failing PCM, but note that since this is a rare event, the fault must be sought elsewhere before any control module is reprogrammed or replaced

How expensive is it to fix code P0404?

As a general rule, replacing the EGR valve on a KIA 1.7 CRDI (D4FD) engine is a challenging procedure even for professional mechanics who have access to all the required tools and equipment. Therefore, having the EGR valve replaced in a professional environment can take up to about five hours, which adds considerably to the final repair bill.

Also, bear in mind that since the most common cause(s) of code P0404 on KIA vehicles often (but not always) involve electrical or wiring issues, diagnosing these kinds of EGR issues often takes up to two hours or sometimes longer, depending on the nature of the problem. So at a minimum, the final repair bill could run to about 5 hours, two of which will typically be charged at a diagnostic rate, which is significantly higher than ordinary labor per hour.

You also have to add the price(s) of all required parts to the labor and diagnostic charges, meaning that the repair bill could run to several hundred dollars, which will typically not include taxes, levies, and fees that may apply to your state or location.

Based on the above, we strongly recommend that you obtain price estimates from at least three or four repair establishments that have proven experience in KIA vehicles to get the most value for your money. Failing to shop around for the best prices could leave you with a repair bill that is higher than you are prepared or able to pay, but having said that, you should expect a repair bill of several hundred dollars.

What are the symptoms of code P0404?

The most common symptoms of code P0404 are largely similar across all applications, and could include one or more of the following-

  • Stored trouble and an illuminated CHECK ENGINE warning light
  • In some cases, multiple additional trouble codes may be present along with P0404 (See the section on Related Codes for details of the most common additional codes that may be present)
  • The vehicle may alternately surge and stumble severely at some or all engine speeds and loads
  • The idling quality may be poor, or the engine may not idle at all
  • The engine may stall unexpectedly or repeatedly at low to moderate engine speeds
  • The exhaust system may emit excessive amounts of black smoke under some operating conditions
  • Varying degrees of power loss may be present at some or all engine speeds and loads
  • A hard-starting condition may be present
  • A strong smell of exhaust gas may be present at some or all engine speeds and loads
  • The vehicle may be locked into a fail-safe or limp mode that severely restricts the engine’s speed and power output. Note that if such a condition is present, it will remain in force until the fault is found and corrected
  • The vehicle will not pass a mandatory emissions test where such periodic tests are required

What are common solutions to code P0404?

The most common solutions to code P0406 on Kia vehicles could include the following-

  • Replace the EGR valve, but take note that this option should ideally only be considered if all of the other repair options listed here have been attempted, but if the issue persists-
  • Inspect all EGR-associated wiring for signs of damage or corrosion, and repair to both industry and OEM standards as required. Note, though, that since damage to wiring is not always visible or detectable during a casual visual inspection, you may need to test all wiring and ground connections with suitable equipment such as a digital multimeter, but be sure to follow OEM-specified or recommended test procedures at all times to avoid causing potentially fatal damage to a) the vehicle’s electrical system or b) one or more control modules, including the PCM
  • Inspect and repair all damaged, perforated, or dislodged vacuum lines as required
  • Use a scan tool with bi-directional control functions to test the operation of the EGR valve to verify that it works as both designed and expected
  • Test the operation of the EGR valve’s position sensor to verify that it works as expected (See the section on Troubleshooting / Difficulty for more details
  • Check to see if the exhaust gas feeder tube is restricted. Clear out restrictions and carbon deposits as required or replace the feed tube
  • Remove the EGR valve and clear out excessive carbon deposits; reinstall the EGR valve and verify that it works as expected

NOTE: Although clogged catalytic converters and overloaded DPF devices can sometimes affect the operation of EGR systems, this is generally not the case where catalytic converter and DPF efficiency codes are not present on the vehicle. In this regard, please note the following-

  • Catalytic converter trouble codes will typically only be set when a converter’s efficiency drops below about 95 to 93 percent, so in the absence of catalytic converter efficiency codes, the causes of code P0404 are unlikely to involve catalytic converter issues
  • If a DPF device regenerates autonomously, the device (and its control system) is still in good working order, and as such, the DPF is unlikely to be the cause of code P0404

How serious is code P0404?

Although a defective or non-functioning EGR valve can cause some drivability issues, it is possible to continue to drive the vehicle for a limited period. However, code P0406 must be considered as somewhat serious, and, therefore, the fault must be found and corrected as soon as possible to avoid causing damage to the engine and other emission control components such as catalytic converters and DPF devices.

How difficult is it to repair code P0404?

Troubleshooting code P0404 will generally involve investigating each of the possible causes of the code as set out elsewhere in this guide, but it should be noted that testing the operation of the EGR valve or its position sensor and their associated wiring involves electrical measurements that require skills and equipment that are generally not available to novice or inexperienced non-professional mechanics.

Such measurements must be performed in a set order and in strict accordance with OEM-level service information to prevent possibly fatal damage to one or more control modules. Thus, based on this fact, we strongly recommend that novice non-professional mechanics do NOT attempt any diagnostic procedure on the wiring of the EGR system of any KIA product because even inadvertent mistakes could cause serious damage to the vehicle’s electrical system.

Thus, if you suspect you are dealing with an EGR system performance issue, the best course of action would be to seek professional assistance with diagnosing and resolving any EGR-related fault code(s)

Below is a list of the EGR-related trouble codes that are most commonly associated with code P0404, but note that codes P0403, P0405, and P0406 are the codes that are the most likely to be present along with P0404-

  • P0403- “Exhaust Gas Recirculation (EGR) Control Circuit”
  • P0405- “Exhaust Gas Recirculation (EGR) Sensor “A” Circuit Low”
  • P0407- “Exhaust Gas Recirculation (EGR) Sensor “B” Circuit Low”
  • P0408- “Exhaust Gas Recirculation (EGR) Sensor “B” Circuit High”
  • P0409- “Exhaust Gas Recirculation (EGR) Sensor “A” Circuit”
  • P0486- “Exhaust Gas Recirculation (EGR) Sensor “B” Circuit”
  • P0489- “Exhaust Gas Recirculation (EGR) Control Circuit Low”
  • P0490- “Exhaust Gas Recirculation (EGR) Control Circuit High”

SPECIAL NOTES: Code P0403 – “Exhaust Gas Recirculation (EGR) Control Circuit” is arguably the most common code to appear along with code P0404. Note that the definition of the code P0403 refers to a malfunction or defect in the EGR system’s electrical control circuit that the PCM cannot identify accurately. However, in most cases, the fault in the (EGR) control system usually, but not always, involves poor electrical connections in the EGR system’s reference voltage or signal circuits that cause the EGR system to operate outside of expected parameters.

Put differently, this means that incorrect, or inaccurate input data can cause the EGR system to work in ways that the PCM does not expect to see based on the engine’s operating conditions at any given point in time. In practice, one possible result of code P0304 is that the EGR valve might allow more or less exhaust gas into the engine than the PCM commands, while another is that the unspecified fault in the EGR system’s control system could cause a cascade of other code to be set, among which could be code P0404 and P0406. END OF SPECIAL NOTES.

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