EGR ERROR CODES

EGR EXHAUST GAS RECIRCULATION

Pre OBD vehicles had no need for an EGC circuit because these older cars had large noisy engines, were relatively fast, were gas guzzlers and  were emitting noxious exhaust emissions as if nobody cared about the environment. When combustion takes place inside an engine's cylinders, nitrogen and oxygen combine to form various oxides of nitrogen; which are collectively termed NOx. NOx emissions are generated as a function of high combustion temperature, so when it was discovered that these noxious gas emissions (NOx) were partly responsible for damaging the ozone layer and contributing to global warming, the EPA recommended legislation for OBD/EOBD/OBD-II systems to be fitted into all cars built after 1996 in order to monitor exhaust emissions.  

VW Engineers then came up with an EGR circuit which took different forms and configurations and were often particular to the make, model and manufacturer of the vehicle. EGR can be achieved either internally by means of valve overlap, or achieved externally by means of a  simple arrangement of pipes and a sprung loaded mechanical valve or an electronically controlled solenoid valve. Some turbo charged engines incorporate a low and high pressure exhaust Gas Recirculation system whereas some non-turbo engines only use high pressure EGR. Engines with diesel particulate filter systems tend to use a fast switching electronically actuated EGR valve, whereas a pneumatically activated EGR valve is employed by several others. Some engines used vacumm controlled EGR and some use water-cooled systems, yet all designed to supplement the traditional air/fuel ratio and spark timing circuit. 

VW 2.5 TDI AXG, AHY &  ACV engine  Pressure Converters,
EGR Valve Control Solenoid, EGR Pressure Feedback Sensor

Today virtually every vehicle manufacturers employ exhaust gas recirculation (EGR) as an emissions control sub-system in their cars, which has become an integral part of OBD-II.  The OBD-II exhaust gas recirculation system monitor is responsible for determining the serviceability of the sensors, hoses, solenoids, valves and actuators that are part of the EGR system and any problem with them would most likely trigger a binary '1' in a readiness test. Readiness tests evaluate eight on-board monitors to gauge the integrity of the engine.  Having said that, On-board diagnostic monitoring predominantly applies to systems that are most likely to cause an increase in harmful exhaust emission and during roadworthy testing these systems are specifically checked to verify compliance with EPA / government regulations.

Modern day EGR circuits essentially consists of electronic components and intelligent computer circuitry capable of recirculating a precisely controlled amount of non-combustible exhaust gas back into the intake manifold. A sort of a feed-back loop if you like. The objective is to  attain  lower combustion temperatures  and obtain optimal NOx reduction at middle and high engine loads. Restated, the greater the EGR the lower the NOx. NOx is poisonous and it is in the interest of every vehicle owner to keep their carbon footprint to a bare minimum.

The components involved in the EGR circuit are, the Mass air flow rate (MAF) sensor G70, Engine Exhaust Gas Temperature (EGT) Sensor 1 G235, Exhaust Gas Temperature (EGT) Sensor 2, Exhaust Gas Temperature (EGT) Sensor 3 G495, Exhaust Gas Temperature (EGT) Sensor 4 G648, EGR Vacuum Regulator Solenoid Valve N18 / N121, Exhaust gas Heated Oxygen Sensor (HO2S) G39, Wastegate Bypass Regulator Valve N75, Hot-film air mass meter G70, Engine  RPM sensor and the position of the EGR Potentiometer G212. EGR Cooler Switch-Over Valve N345, which are all vehicle dependent. These transducers  assists the Engine Control Module to recognizes the position of the spring loaded valve plate so that it can adjusts the actuator (electric controlled motor) that in turn controls the gas return flow so that it can  mix with a portion of  fresh air entering at the intake manifold. This lowers the internal combustion temperature and reduces the formation of oxides of nitrogen and keep it well within the legal limit.

However, when this doesn't happen, Engine performance is un-noticeably lower, causing the Glow Plug Indicator Light to flash  continuously  in the case of diesel powered vehicles and the Engine management light in the case of gasoline powered vehicles. Meanwhile the ECU will also register a DTC in its non-volatile fault memory. In the event of a EGR malfuntion which wound't normally be noticed by  the driver if it wasn't for the instrument cluster light that flashes or stays on, don't just start replacing components. First and foremost clean out any carbon buildup with Wynnes EGR 3 cleaner, then check the sensor harness and their respective connectors and check solenoids for continuity.

The likeness of the EGR valve can be compared to the throttle valve, both are butterfly plates that are electronically controlled by the ECU causing them to open and close dependent on the calculated duty cycle of the generated drive pulse. The wider the throttle opens the higher the engine will rev, likewise the wider the EGR valve opens the better the engine performs and the less NOx it produces.

EGR ERROR CODES

Error codes staring at P0400 - P0409 ranges from malfunction of N18 (EGR Valve) to low/high signals from G98 (EGR Temperature sensor) to spurious signals from G212 (potentiometer)

Error codes staring at P1400 - P1408 ranges from Electrical Malfunction, to   Short to Ground/ Positive, too low or high

Error codes  P042E &  P042F dictates that the Exhaust Gas Recirculation "A" Control valve is, Stuck Open and stuck Closed respectively.

Error codes   P045E & P045F dictates that the Exhaust Gas Recirculation "B" Control valve is, Stuck Open and stuck Closed respectively. ts fairly pevalent on VW Jetta.

Error codes P2BAB & P2BAC dictates on incorrect EGR Flow, that NOx levels have exceeded and that the EGR has been deactivated.  Its fairly prevalent on the VW Crafter.

Once your problem is solved, it is imperative that you put  your VW, Audi, Skoda or Seat  vehicle, through a drive cycle but remember the drive cycle is manufacturer specific and should be executed accordingly.