Emissions control: EGR, DPF, catalytic converter and AdBlueGeneric OBD-II codeUrgency: Garage soon
Code P2BAC: excess NOx due to EGR deactivation
P2BAC means: excess NOx: EGR (exhaust gas recirculation) deactivation.[1][2][3] It is a code for diesel engines with NOx sensors and exhaust gas recirculation (EGR). TaT describes it as informative rather than the fault of a component: the control unit stores it after it has deactivated or heavily limited the EGR because of another fault, and as a consequence the NOx emissions exceed the legal limit. That is why it rarely appears on its own: it reflects a decision made by the control unit itself.[1][2][3]
What code P2BAC means
It is a code for diesel engines with NOx sensors and exhaust gas recirculation (EGR). TaT describes it as informative rather than the fault of a component: the control unit stores it after it has deactivated or heavily limited the EGR because of another fault, and as a consequence the NOx emissions exceed the legal limit. That is why it rarely appears on its own: it reflects a decision made by the control unit itself.[1][2][3]
The EGR returns part of the exhaust gases to the intake to lower the combustion temperature, which reduces the formation of NOx (Wikipedia). With the EGR deactivated, the engine loses that help and NOx emissions rise.[4]
TaT indicates that it is seen mainly on Volkswagen Group vans and pick-ups, such as the Crafter, the Amarok and the Transporter. It is a generic code of the OBD-II standard (it starts with P2), with the same definition on any brand.[1][5]
Original definition (SAE J2012): NOx Exceedance - Deactivation of EGR[1][2][3]
Causes of P2BAC
From most to least likely, according to the sources.
- 1Another fault stored in the control unit that has led it to deactivate the EGR. It is the first thing to look for, because P2BAC is the consequence, not the cause.[1]
- 2Faulty or blocked EGR valve (for example, by carbon).[2][6][7]
- 3Faulty NOx sensor, or an open or short-circuited sensor circuit.[2][6]
- 4Dirty or faulty intake (MAP) or exhaust pressure sensor.[2][6]
- 5Damaged or blocked particulate filter, according to CarWiki.[2]
- 6Poor wiring or connections in the EGR circuit or earths.[6]
- 7Control unit needing a software update or a correct calibration of the exhaust gas treatment.[2][6]
Symptoms
- Engine fault warning light on and a code stored in the control unit.[6]Engine warning light: faults that cause it
- Less power and acceleration.[2][6]Less power: faults that cause it
- Black smoke from the exhaust.[2][6]Black smoke: faults that cause it
- Higher fuel consumption.[2][6]Uses more fuel: faults that cause it
- Irregular engine running, with jerking.[2][6]Jerking: faults that cause it
- NOx emissions rising above the limit.[1][2]
How to diagnose P2BAC
In order: from the most likely and cheapest to check to the most expensive.
- 1Read all the codes and the freeze frame data, and note them before clearing anything. Look for the fault that caused the deactivation: EGR, NOx sensor, pressure sensors or particulate filter.[1][6]
- 2Repair those other codes first. P2BAC usually disappears when the cause is corrected; if it is only cleared, the control unit will deactivate the EGR again.[1]
- 3Inspect the wiring and connectors of the NOx sensor and the EGR sensors, and repair or replace anything burnt, loose or corroded.[6]
- 4Check the EGR valve (carbon blockage and electrical operation) and the EGR cooler, and clean or replace them if appropriate.[2][6][7]
- 5Check the NOx and pressure sensors and the condition of the particulate filter.[2][6]
- 6Before condemning the control unit, look for technical bulletins for your model and a possible software update.[2][6]
- 7After repair, clear the code, carry out a road test and check that it does not return and that no others appear.[2][6]
Can I keep driving with P2BAC?
Garage soon
The sources do not set a deadline or say whether the car goes into limp mode. What they do describe is that the EGR is deactivated, that NOx emissions exceed the limit, and that loss of power, black smoke and higher consumption may appear. It is worth locating the fault that caused it soon.[1][2][4]
Parts related to code P2BAC
The parts that most often cause this code. The code points to the circuit, not always the part: diagnose before you buy.
EGR valve
Particulate filter
Affiliate links: if you buy from these shops, MotorFiable may receive a commission at no cost to you. Check compatibility against the registration plate or VIN before ordering. Affiliate links
Documented faults related to P2BAC
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.
Engine sensors: the most serious faults by engine and car
- High severityFrequency: 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 severityFrequency: 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 severityFrequency: 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 severityFrequency: 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.
Particulate filter (DPF/FAP): the most serious faults by engine and car
- 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
- High severityFrequency: Common1.3 MultijetIncomplete particulate filter regenerations and oil dilutionIn heavy urban use, with short journeys that do not let the particulate filter regeneration finish, unburnt diesel passes into the sump and dilutes the oil; the level can rise on the dipstick and the oil loses its ability to lubricate. Repeated many times, it speeds up engine wear.
- High severityFrequency: Common2.0 HDiDPF clogging on additive-type systems (Eolys/cerine)The additive-type diesel particulate filter (DPF) of the 2.0 HDi clogs relatively easily on short journeys, especially on the 107/110 and 136-140 hp versions. The anti-pollution warning light comes on and, if ignored, the car loses power and may end up needing a new DPF.
- High severityFrequency: Common1.6 and 2.0 MultiJet IISaturated diesel particulate filter (DPF) from incomplete regenerationsIn urban use with short journeys, the particulate filter does not manage to complete its regeneration and becomes saturated; garages recommend a weekly motorway run to avoid it. The filter itself is among the weak points flagged in the 1.6 and 2.0 MultiJet II after a certain mileage.
P2BAC by make
Documented faults that can trigger P2BAC in each make's engines and cars.
- P2BAC on Opel14
- P2BAC on Volkswagen12
- P2BAC on Fiat10
- P2BAC on Ford10
- P2BAC on Nissan10
- P2BAC on Seat10
- P2BAC on Škoda10
- P2BAC on Toyota10
- P2BAC on Alfa Romeo9
- P2BAC on Audi9
- P2BAC on Renault9
- P2BAC on Volvo9
- P2BAC on Citroën8
- P2BAC on Mazda8
- P2BAC on Peugeot8
- P2BAC on Hyundai7
- P2BAC on Kia7
- P2BAC on MINI6
- P2BAC on Jeep5
- P2BAC on Mercedes-Benz5
- P2BAC on Suzuki5
- P2BAC on Chevrolet4
- P2BAC on DS4
- P2BAC on Honda4
- P2BAC on Jaguar4
- P2BAC on Lancia4
- P2BAC on Land Rover4
- P2BAC on Mitsubishi4
Frequently asked questions
What does “EGR deactivation” mean in P2BAC?
That the control unit has switched off, or heavily restricted, exhaust gas recirculation because of another fault, and that in doing so the NOx emissions have exceeded the legal limit. TaT describes it as an informative code about that decision, rather than the fault of a specific component.[1][4]
Does the EGR valve need replacing when P2BAC appears?
Not necessarily. As the code is the consequence of another fault, the first step is to read the other stored codes. The EGR valve, the NOx sensor, the pressure sensors and the particulate filter are among the possible causes, and only the part that is shown to be faulty is replaced.[1][2][6]
Why does it not appear on its own?
Because the control unit stores it as a result of having deactivated the EGR due to another fault. According to TaT, it rarely appears on its own; in practice the accompanying code should be dealt with first.[1]
Will I pass the MOT with code P2BAC?
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.[8]
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.
- P2BAC - NOx Exceedence - Deactivation of EGR | TaTThe Automotive Technician (TaT) · Technical documentation · consulted 31 October 2026
- OBD DTC Fehlercode P2BAC | NOx Überschreitung – Deaktivierung der Abgasrückführung (EGR)CarWiki.de · Technical documentation · consulted 31 October 2026 · in German
- p2bac Generic DTC: NOx Exceedence - Deactivation of EGRDTCSearch.com (OBD Solutions) · Technical documentation · consulted 31 October 2026
- Exhaust gas recirculationWikipedia · Other source · consulted 31 October 2026
- On-board diagnosticsWikipedia · Other source · consulted 31 October 2026
- OBD II Error Code P2BAC SolutionPartsAvatar · Technical documentation · published 1 June 2022 · consulted 31 October 2026
- ¿Qué es el sistema antipolución del coche y qué averías puede sufrir?RACE · Motoring press · consulted 31 October 2026 · in Spanish
- 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