Emissions control: EGR, DPF, catalytic converter and AdBlueGeneric OBD-II codeUrgency: Garage soon
Code P0403: faulty EGR control circuit
P0403 means: exhaust gas recirculation (EGR): circuit malfunction.[1][2] P0403 is not about how much gas is recirculating, but about the circuit that controls the EGR: the control unit has detected an electrical fault in it and the valve is not responding to its commands. Autodoc explains it as a voltage in the EGR solenoid circuit that does not match the engine's situation at that moment.[1][2][3]
What code P0403 means
P0403 is not about how much gas is recirculating, but about the circuit that controls the EGR: the control unit has detected an electrical fault in it and the valve is not responding to its commands. Autodoc explains it as a voltage in the EGR solenoid circuit that does not match the engine's situation at that moment.[1][2][3]
The sources approach it in two ways. Autodoc, Carista and TAT treat it as an electrical fault in the control circuit (solenoid, wiring, open circuit or short circuit). Pierburg describes it as incorrect or inconsistent EGR signals caused by wear or dirt on the valve potentiometer or the temperature sensor. On VW common rail TDIs with a fully electric EGR, Ross-Tech states that the code points to the EGR valve on the intake manifold itself.[1][2][3][4][5]
It is a generic OBD-II code: the 0 after the P indicates that it is defined by the SAE standard, so it means the same on any make.[6]
Original definition (SAE J2012): Exhaust Gas Recirculation Circuit Malfunction[1][2]
Causes of P0403
From most to least likely, according to the sources.
- 1Faulty internal solenoid coil or EGR valve motor (open circuit or short circuit), so the valve does not move when commanded.[2][3][5]
- 2Damaged wiring or connector between the valve and the control unit: breaks, chafed or short-circuited wires, corrosion or moisture.[1][2][3][5]
- 3Blown valve fuse.[5]
- 4Valve seized by soot, open or closed, so it cannot give valid position feedback.[3]
- 5Excessive resistance in the circuit or loss of the reference voltage that supplies the solenoid.[1]
- 6Wear or dirt on the valve position potentiometer or the EGR temperature sensor, giving inconsistent signals.[4]
- 7On EGR valves with a vacuum solenoid, a jammed control solenoid.[1]
Symptoms
- Engine warning light on.[1][3][5]Engine warning light: faults that cause it
- Unstable idle.[1][3][5]Vibrations: faults that cause it
- The engine may stall.[5]Engine stalls: faults that cause it
- Loss of power, slight or more noticeable depending on the position in which the EGR is stuck.[3][5]Less power: faults that cause it
- Hesitation or problems accelerating.[1][3]Jerking: faults that cause it
- Combustion knock or pinking at low load, and more NOx.[3]
- The car fails the emissions test until the EGR monitor completes without errors.[3]
How to diagnose P0403
In order: from the most likely and cheapest to check to the most expensive.
- 1Start with the cheapest checks: check the fuses and that power and earth reach the valve connector.[3][5]
- 2Inspect the wiring and connectors: breaks, chafing, corrosion and moisture in the solenoid wires.[1][3][5]
- 3With the diagnostic tool, command the valve to open and close and watch its actual position in the live data; if it is a solenoid, you should hear a click when it is activated.[1][3]
- 4Measure the valve coil or motor: if it shows an open circuit or short circuit, it is faulty. On a solenoid, disconnect it and check that there is no short circuit to earth in the control wire (the resistance should be infinite).[1][3]
- 5On VW and Audi, check the valve's measuring value blocks before replacing it.[5]
- 6If the position signals look inconsistent, compare them with the reference values: wear or dirt on the potentiometer can distort them.[4]
- 7If the valve has to be replaced, then clean the soot out of the EGR passages so that the new one does not clog up.[3]
Can I keep driving with P0403?
Garage soon
Autodoc advises against driving normally while the fault persists, although it considers that it does not usually cause very serious problems in the short term, and asks for it to be repaired as soon as possible to avoid greater damage. Carista gives it medium severity and notes that the EGR can end up stuck in an incorrect position, with unstable idle, hesitation or loss of power.[1][3]
Documented faults related to P0403
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
EGR valve: the most serious faults by engine and car
- Critical severityFrequency: Very frequentBMW B47EGR cooler leaks with risk of engine fireYes: the EGR valve cooler can suffer internal coolant leaks which, mixed with soot and oil, can reach combustion temperatures; BMW has launched several technical campaigns since 2018 to inspect and replace it because of the risk of engine fire.Repair (garage): €500–€1,500
- Critical severityFrequency: Very frequentBMW N57EGR cooler leaks with risk of engine fireYes: like the N47 and B47, the N57 is covered by BMW's service campaign for EGR cooler leaks, which can mix coolant with soot and oil to combustion temperatures. BMW checks free of charge the 6-cylinder engines built between July 2012 and June 2015 because of the fire risk.
- High severityFrequency: Very frequentOM651EGR and particulate filter clogging, and emissions software updatesThe particulate filter and EGR clog up with short journeys, as on any diesel with these systems. In addition, Germany's KBA required software updates on several models with this engine between 2018 and 2021 because of a function that reduced EGR outside a temperature range.Repair (garage): €800–€2,500
- Medium severityFrequency: Very frequentOM642Emissions defeat device (AdBlue/EGR) and software update campaignGermany's KBA found indications of emissions manipulation in cars with the OM642 engine (alongside the OM651): AdBlue dosing and the EGR changed between the test bench and the road. Mercedes-Benz denied it, but in 2018 it recalled hundreds of thousands of diesels in Europe.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- Critical severityFrequency: Occasional1.6 GDi híbrido (Kappa)Main relay of the power relay assembly (overheating and fire risk)Yes, on the first units: Hyundai and Kia recalled 2016–2018 Ioniq and Niro hybrids and plug-in hybrids because the main relay that connects the high-voltage battery could come loose, overheat and, in the worst case, cause a fire.
- Critical severityFrequency: Occasional1.6 GDi híbrido (Kappa)Clutch hydraulic actuator (HCA): leak or moisture with risk of short circuit and fireYes, this is the most documented hybrid system fault: the hydraulic actuator that engages the combustion engine with the hybrid assembly has had two recalls (2018 for a leak on the Niro and 2025 for moisture in its electronic board on the Niro, Ceed and XCeed PHEV), with a risk of short circuit and fire.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Frequently asked questions
What is the difference between P0403 and P0404?
P0403 points to a fault in the EGR control circuit: the valve does not respond to the control unit's commands, which is why you investigate fuses, wiring, connectors and the valve solenoid or motor first. P0404 is the circuit "range/performance" code, another one from the same family. Pierburg separates them like this: P0403 as a control loop fault, with incorrect or inconsistent EGR signals, and P0404 as a measurement or performance problem, with recirculation outside the expected range.[2][3][4][5]
Does P0403 always mean the EGR valve has to be replaced?
No. The causes include a blown fuse, damaged wiring or connectors, moisture in the solenoid wires, excessive resistance in the circuit, or a valve seized by soot, as well as a faulty valve coil or motor itself. That is why it is worth checking fuses, power, earth and wiring before replacing anything; and if the valve was seized by soot, clean the passages afterwards so the fault does not come back.[1][3][5]
How do you check the EGR circuit?
With a diagnostic tool you command the valve to open and close and watch its actual position in the live data; if it does not respond, you check power and earth at its connector. On a solenoid you should hear a click when it is activated, and measuring the resistance of the coil or motor shows whether there is an open circuit or short circuit. On VW and Audi, you also check the measuring value blocks.[1][3][5]
Can I drive with code P0403?
Autodoc does not recommend it while the fault persists, because the symptoms (unstable idle, problems accelerating) make driving difficult, although it does not believe it causes very serious problems in the short term; it asks for it to be repaired as soon as possible. Carista rates it as medium severity.[1][3]
Does P0403 mean the same on all makes?
In the definition, yes: it is a generic OBD-II code and those starting with P0 are defined by the SAE standard. What varies is the type of EGR (with a vacuum solenoid or fully electric) and how each manufacturer presents the code; VW and Audi, for example, show it as an EGR valve N18 malfunction.[5][6]
Will I pass the MOT with code P0403?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[7]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- Código OBD2 P0403: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
- P0403: Exhaust Gas Recirculation Circuit MalfunctionThe Automotive Technician (TaT) · Technical documentation · consulted 2 October 2026
- P0403: OBD-II code P0403 means the PCM has detected an electrical fault in the EGR control circuitCarista · Technical documentation · consulted 2 October 2026
- OBD-SystemMS Motorservice (Pierburg) · Manufacturer · consulted 2 October 2026
- Fault Code 16787/P0403/001027Ross-Tech Wiki · Technical documentation · consulted 2 October 2026
- On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish