Exhaust gas neutralisation with SCR system. What is it for?
An effective way to reduce nitrogen oxides in exhaust gases (EG) is to neutralise them using SCR. The acronym SCR stands for Selective Catalytic Reduction. This system is specifically designed to reduce nitrogen oxides in the exhaust gas.
The way the system works is that nitrogen oxides (NOx) in the exhaust gas react with ammonia (NH3) to convert it into non-toxic nitrogen (N2) and water (H2O). This chemical process refers to reduction reactions and takes place in the vehicle’s reduction neutraliser. The ammonia required for the reduction reaction is obtained from an aqueous solution of urea or AdBlue® reducing agent. This takes place under the influence of the exhaust gas heat. The AdBlue® reducing agent is located in the vehicle in a separate additional tank and is permanently injected into the exhaust gas path upstream of the reducing catalyst.
Below is a schematic of the Adblue (SCR) system using the VW Passat B8 as an example.
So what should you do in case of system problems?
In case of a breakdown of the Adblue (SCR) system, the car may block the start of the engine (if you have, for example, a VCDS diagnostic system, you can unblock the start and drive to the service station yourself). In this case the system should be repaired as soon as possible, but here motorists face difficulties with availability of spare parts or the price of spare parts.
If it is difficult or costly to repair, it is possible to disable the Adblue system (SCR) in the engine control unit of the car. Once disconnected, there is no need to repair anything or refill the Adblue fluid.
Answering the most common questions::
- 1. How is the engine control unit flashed?
– In most cases via the OBD diagnostic connector. - 2. Do I need to remove the EGR valve and particulate filter?
– No, it is not necessary. Only Adblue (SCR) can be deactivated, and the EGR valve and particulate filter will work as normal. - 3. What negative consequences can be after flashing?
– We often receive cars where the Adblue (SCR) system was incorrectly or crookedly disabled. The consequences are very different. For example, the car does not start, but there are no errors. Also there may be difficulties with diagnostics, if extra errors are wiped off illiterately, etc.
You need to take seriously the choice of a company to disable Adblue (SCR). - 4. Will consumption increase?
– No. - 5. Does disabling Adblue (SCR) affect the car’s power dynamics?
– No. - 6. What are the causes of Adblue (SCR) failure?
– Poor quality fluid, damaged or oxidized wiring connectors, the system consists of many components that can fail. - 7. Can Adblue (SCR) be removed from the warranty?
– Yes. - 8. Will it smoke more without Adblue (SCR)?
– No. If the EGR and particulate filter remain in normal operation.
Frequent Adblue (SCR) errors:
- 28922 – Reductant
P20E8 00 [237] – Pressure too low - 9656 – Reductant tank heater on
P202B 00 [237] – Short to ground - 22585 – Reductant level sensor
P203B 00 [237] – Invalid signal - 21378 – Reductant dosing module
P20FE 00 [101] – Malfunction - 11393 – Reductant level sensor
P204B 00 [096] – Invalid signal - 14416 – Heating system output stage reducing agent
P20B7 00 [175] – short to ground - 9655 – Reductant tank heater on
P202A 00 [237] – open circuit - 16936 – Reductant heating element 2 on
P20BD 00 [032] – open circuit - 9654 – Reductant heating system output stage
P148B 00 [040] – malfunction - 9650 – Reductant heating system output stage 2
P148C 00 [175] – malfunction - 28648 – Specified in ISO document 15031-6
P206B 00 [237] – 2005
P206B – Reductant quality sensor invalid signal - 9617 – Reductant heating element 1 on
P20B9 00 [10101111] – open circuit - 9636 – Reductant purge valve
P20A0 00 [10101111] – open circuit - 9686 – Reductant tank temperature sensor
P205A 00 [10101111] – electrical malfunction - 10098 – Reductant pump 1 control signal supply
P208B 00 [01100101] – invalid signal - 18612 – Reductant
P207F 00 [01100101] – insufficient efficiency - 28416 – Reductant level sensor/Tank temperature
U121D 00 [10101111] – no communication - 9687 – Reductant tank temperature sensor
P205C 00 [10101111] – short to ground - 41157 – Reductant level sensor
P203F 00 [00100111] – weak signal
- 17277 – SCR; NOx Catalyst; Bank 1
P20EE 00 [101] – Efficiency Too Low - 9879 – NOx Sensor 1 Heating Element; Bank 1
P2209 00 [101] – Invalid Signal - 9574 – NOx Sensor 1; Bank 1
P2200 00 [096] – Electrical Malfunction - 9580 – NOx Sensor 1; row 1
P2201 00 [096] – invalid signal - 9690 – NOx sensor
P1032 00 [096] – signal level too high - 28992 – NOX sensor 2
U029E 00 [175] – no communication - 9567 – NOx sensor 2; Row 1
P229F 00 [237] – invalid signal - 9688 – Reductant tank temperature sensor
P205B 00 [109] – invalid signal - 9654 – Reductant heating system output stage
P148B 00 [040] – malfunction - 9650 – Reductant heating system output stage 2
P148C 00 [175] – malfunction - 37062 – Reductant quality control module
U02A2 00 [175] – no communication - 9611 – Reductant injector; Row 1
P2047 00 [039] – Open Circuit - 9561 – NOx Sensor 2; Row 1
P229E 00 [175] – Electrical Malfunction - 9880 – NOx Sensor 2 Heating Element; Row 1
P22A7 00 [172] – invalid signal - 29630 – Reductant flow
P218F 00 [237] – not recognized - 28413 – Reductant level sensor
P203D 00 [036] – short circuit to positive - 9639 – Reductant pump 1 control signal supply
P208A 00 [10101111] – open circuit - 9633 – Reductant level sensor
P203A 00 [10101111] – electrical malfunction - 9684 – Pressure sensor restorer
P204A 00 [10101111] – electrical malfunction
VAG vehicles with TDI engines
AUDI A4
AUDI A6
AUDI Q3
AUDI Q5
AUDI Q7
Golf Mk7/Mk8
Passat B7/B8/NMS
Touareg
Tiguan
Transporter/Multivan
SuperB
Kodiaq
Karoq
Leon
Arona
Ateca
Tarracco