Emissions control: EGR, DPF, catalytic converter and AdBlueGeneric OBD-II codeUrgency: Garage soon
Code P0402: excessive EGR flow
What code P0402 means
The ECU detects that more exhaust gas is being recirculated than it expected: the EGR valve lets through more than the engine management commands, for example because it sticks open or does not fully close.[1][2][4]
It is the opposite case to P0401. Because the excess exhaust gas dilutes the air entering the engine, the symptoms show up mainly at light throttle, which is when the EGR works hardest: rough idle, hesitation, loss of power or even stalling.[2][3]
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. What changes is the valve's construction (pneumatic, electric or electromotive) and the most likely cause on each engine.[4][5]
Original definition (SAE J2012): Exhaust Gas Recirculation Flow Excessive Detected[1][2][3]
Causes of P0402
From most to least likely, according to the sources.
- 1EGR valve stuck in the open position or not fully closing, often because carbon deposits stop it seating.[1][2][4][6]
- 2Leaks in the EGR system: deteriorated EGR gasket or cracked pipe.[1][2][6]
- 3Faulty EGR position sensor or EGR temperature sensors.[1][4]
- 4Faulty or dirty air flow meter (mass air flow sensor).[4]
- 5On pneumatically operated valves, damaged vacuum hoses, a ruptured diaphragm or a damaged stem; on electronic systems, a control solenoid valve or solenoid stuck open.[1][2]
- 6Faulty, loose or corroded valve wiring or connectors.[1][6]
- 7Fault in the EGR control in the ECU.[1]
Symptoms
- Engine warning light on; Autodoc says it may be steady or flashing.[1][2][6]Engine warning light: faults that cause it
- Rough idle.[1][2][6]Vibrations: faults that cause it
- The idle may stumble or the engine may stall, because the excess exhaust gas dilutes the intake air.[2]Engine stalls: faults that cause it
- Hesitation when accelerating at light throttle, which is when the EGR is most active.[2]Jerking: faults that cause it
- Loss of power when accelerating.[1][2][6]Less power: faults that cause it
- Hard starting, especially when cold.[1]Hard to start: faults that cause it
- Increased fuel consumption.[1]Uses more fuel: faults that cause it
- Black smoke from the exhaust.[1]Black smoke: faults that cause it
- Higher emissions and a possible failure of the emissions test until the EGR monitor completes without errors.[2][6]
How to diagnose P0402
In order: from the most likely and cheapest to check to the most expensive.
- 1Check the simplest things first: vacuum hoses, EGR gaskets and pipes (looking for leaks), and the valve's connectors and wiring.[1][2][6]
- 2With the diagnostic tool, command the EGR closed with the engine idling: if the idle does not settle, the valve has stuck open.[2]
- 3Remove the valve and look for carbon on the seat that stops it closing; clean or replace it depending on its condition, and clean the EGR system.[1][2][6]
- 4Check the EGR position sensor, the temperature sensors and the air flow meter, and compare their readings with the reference values.[1][4]
- 5On electronic systems, check whether the control solenoid valve or solenoid has stuck open; on pneumatic ones, the diaphragm and the vacuum lines.[2]
- 6If the valve was stuck, find out why it gets dirty (injection system, crankcase oil vapour separator) so that the problem does not come back.[4]
- 7If everything is in order, check whether there is an ECU software update and carry out a full diagnosis with professional equipment.[1]
Can I keep driving with P0402?
Garage soon
Autodoc Club allows short journeys, but asks for it to be corrected promptly, because a faulty EGR can damage the engine and increase emissions; Carista classes it as medium severity. If the valve sticks open, the engine may hesitate or stall, according to Carista, which makes it difficult to drive normally.[1][2]
Documented faults related to P0402
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Faults in which this code appears
EGR valve: the most serious faults by engine and car
- Critical severityVery frequentFrequency: 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 severityVery frequentFrequency: 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 severityVery frequentFrequency: 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 severityVery frequentFrequency: 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.
Carbon build-up in the intake: the most serious faults by engine and car
- Medium severityVery frequentFrequency: Very frequent2.0 TSI / TFSICarbon build-up on the intake valvesBecause the fuel is injected directly into the cylinder, no petrol washes over the intake valves, so oil residue and soot build up and, over the years, restrict airflow and affect engine response.
- Medium severityCommonFrequency: Common1.6 HDiLeaks at the injector washers and carbon build-up in the cylinder headIt is common for the copper washers of the 1.6 HDi injectors to stop sealing: the engine blows gases, carbon forms around the injector and soot gets into the oil. It is cheap to repair, but if left it contaminates the oil and is one of the causes of turbo failure.Repair (garage): €110–€310
- Medium severityCommonFrequency: Common1.0 T-GDICarbon build-up on the intake valves and coking of the injectorsThe direct injection on the 1.0 T-GDI does not wash the intake valves with fuel, so over the kilometres carbon builds up on them and on the injectors. It causes loss of power, jerking and higher fuel consumption; it is fixed by cleaning the manifold and valves, without damaging the engine.
- Medium severityCommonFrequency: Common1.6 GDI / T-GDICarbon build-up on the intake valvesBeing pure direct injection, with no port injectors to wash the valves, the 1.6 GDI and T-GDI build up intake carbon with mileage: unstable idle, jerking or loss of power. A design trait of all direct injection, not a manufacturing fault.
Engine sensors: the most serious faults by engine and car
- High severityOccasionalFrequency: Occasional2.0 DTI and 2.2 DTIVP44 injection pump and air mass meter failureGerman Wikipedia documents recurring failures of the Bosch VP44 injection pump and the air mass meter in the early years of this engine. An owner testimony for this engine describes the pump being replaced at 192,500 km, at a cost the owner calls «prohibitive».
- Medium severityCommonFrequency: Common2.0 TDIClogged particulate filter or faulty pressure sensorThe 2.0 TDI's particulate filter clogs if the car mostly makes short journeys, because it never gets to regenerate; sometimes the fault is just the differential pressure sensor. Cleaning it costs around €200 and replacing it, €800 to €3,000.Repair (garage): €800–€3,000
- Medium severityCommonFrequency: Common1.4 and 1.6 8vCrankshaft position sensor failure (TDC sensor)The crankshaft position sensor (capteur PMH, or TDC sensor) appears repeatedly in the reliability sources for the Clio II, the Kangoo I and the Dacia Logan I with this engine, with hard cold starting or stalling as the main symptoms. It is a cheap part, but the failure can leave you stranded.
- Medium severityCommonFrequency: Common1.4 and 1.6 16vCrankshaft position sensor failureThe crankshaft position sensor (capteur PMH) appears repeatedly in the reliability sources for almost every generation with this engine, with hard cold starting, stalling or the car cutting out unexpectedly. It is a cheap part, but the failure can leave you stranded.
Frequently asked questions
What is the difference between P0402 and P0401?
They are opposite cases. P0402 indicates that more exhaust gas is being recirculated than expected, normally because the EGR valve sticks open or does not fully close; P0401 indicates that less is being recirculated, mainly because soot is blocking the passage or because a valve is not opening fully.[3][4]
Why can P0402 make the engine jerk or stall?
With the valve open too far, too much exhaust gas enters the intake and dilutes the air reaching the engine. Carista explains that this causes rough idle, hesitation or stalling, and that the lack of power is noticeable mainly at light throttle, which is when the EGR works hardest. TAT lists similar symptoms: rough idle, hesitation and stalling.[2][3]
How do you check whether the EGR valve is stuck open?
With a diagnostic tool you command the EGR closed with the engine idling: if the idle does not settle, the valve is open. Then it is removed to look for carbon on the seat, and the gasket and pipe are checked and, on electronic systems, the control solenoid. Ross-Tech, for VW and Audi, sums up the process as checking or cleaning the EGR system, checking or replacing the valve and checking its wiring.[2][6]
Can I drive with code P0402?
For short journeys and with the intention of repairing it soon. Autodoc Club allows it on that condition because a faulty EGR can damage the engine and increase emissions, and Carista classes it as medium severity. If the engine stalls or jerks, it is not advisable to keep driving normally.[1][2]
Does P0402 mean the same on all makes?
Yes. It is a generic OBD-II code: those starting with P0 are defined by the SAE standard and have the same definition across all manufacturers. Each make may display it with its own wording (VW shows it as "EGR: excessive flow"), but the meaning is the same.[5][6]
Will I pass the MOT with code P0402?
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.
- 1.Código OBD2 P0402: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
- 2.P0402: OBD-II code P0402 flags excessive EGR flowCarista · Technical documentation · consulted 2 October 2026
- 3.P0402: Exhaust Gas Recirculation Flow Excessive DetectedThe Automotive Technician (TaT) · Technical documentation · consulted 2 October 2026
- 4.OBD-SystemMS Motorservice (Pierburg) · Manufacturer · consulted 2 October 2026
- 5.On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- 6.Fault Code 16786/P0402/001026Ross-Tech Wiki · Technical documentation · consulted 2 October 2026
- 7.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