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SCR, Selective Catalytic Reduction - the aftertreatment system that converts nitrogen oxides in the exhaust into nitrogen and water, by injecting a urea solution into the hot exhaust stream upstream of a catalyst.
HI-eSCR - FPT's name for its SCR-only aftertreatment architecture. On Tier 4 Final and Stage IV engines it consists of a diesel oxidation catalyst and an SCR catalyst, with no particulate filter and no exhaust gas recirculation.
DOC, Diesel Oxidation Catalyst - a passive catalyst ahead of the SCR catalyst. It oxidises carbon monoxide and unburnt hydrocarbons, and converts part of the NO into NO2, which makes the SCR reaction downstream faster. It has no sensors and no moving parts.
DPF, Diesel Particulate Filter - a filter that traps soot and periodically burns it off. Not fitted to the Tier 4 Final FPT machines covered here. It appears on Stage V machines, which is one of the reasons a Stage V machine is a different platform.
EGR, Exhaust Gas Recirculation - routing part of the exhaust back into the intake to lower combustion temperature. Not fitted to the machines covered here; FPT reached Tier 4 Final without it.
The SCR system has a vocabulary of its own, and manufacturers use different words for the same part. This is what the terms on this page mean.
AdBlue - the trade name, in Europe, for the urea solution injected into the exhaust. Known as DEF, or Diesel Exhaust Fluid, in North America. The two are the same product.
Urea concentration - AdBlue is 32.5 per cent urea in demineralised water. That figure is not approximate: the ECU monitors it and logs a fault outside a narrow band around it.
Crystallisation - urea deposits forming as solid white crystals where AdBlue dries out, typically at the injector tip and inside the dosing line. The most common mechanical failure in the whole system.
Ammonia slip - unreacted ammonia passing through the SCR catalyst and out of the exhaust. It happens when more AdBlue is dosed than the catalyst can use, and it is what the NH3 sensor exists to detect.
Denoxtronic - Bosch's AdBlue dosing system. The machines covered here use Denoxtronic 2.2. Other generations, such as 6.3 on the smaller FPT F5 engine, are different systems with different control units and are not interchangeable.
Supply module, or pump module - the unit that draws AdBlue from the tank, filters it and delivers it under pressure to the doser valve. It also runs a purge cycle at shutdown to clear the line.
Doser valve, or injector - the metering valve that sprays AdBlue into the exhaust ahead of the SCR catalyst. It opens into a hot gas stream, which is why crystallisation concentrates here.
NOx sensor, upstream - measures nitrogen oxides entering the SCR catalyst. The ECU uses this reading to calculate how much AdBlue to dose.
NOx sensor, downstream - measures nitrogen oxides leaving the SCR catalyst. Comparing it against the upstream reading is how the ECU judges whether the system is working.
NH3 sensor - measures ammonia downstream of the catalyst, detecting ammonia slip.
AdBlue quality sensor - measures urea concentration in the tank.
Level and temperature sensors - monitor how much AdBlue is in the tank and how warm it is. AdBlue freezes at about −11 °C, so the tank and lines are heated.
ECU, Engine Control Unit - the computer that manages the engine and its aftertreatment. On the machines covered here it is a Bosch EDC17CV41. The part number is printed on a label on top of the unit, above the connectors, and it is what determines compatibility.
CAN bus - the network the sensors and control units use to talk to each other. Both NOx sensors are intelligent devices on this bus rather than simple analogue sensors.
J1939 - the SAE standard that defines how diagnostic faults are numbered on commercial and off-highway vehicles. It is the source of the SPN and FMI numbering above.
SPN, Suspect Parameter Number - identifies which component or measurement the fault relates to.
FMI, Failure Mode Identifier - identifies what kind of failure it is: open circuit, out of range, drifted, and so on.
Inducement - the staged restriction the ECU applies when an emissions fault is not repaired: a dashboard warning, then reduced torque, then a limited engine speed. The stages and their timing are set by emissions regulation, not by the manufacturer.
Derate - the torque reduction stage of inducement. The engine runs, but not at full output.
Limp mode - the final stage, where engine speed is limited. The machine can be moved but cannot do useful work.
Tier 1 to Tier 3 - the earlier US EPA standards for non-road diesel engines, phased in between 1996 and 2008. These engines met their limits inside the cylinder, through injection and combustion control. There is no aftertreatment, no AdBlue and no NOx sensor, so none of the faults described on this page can occur.
Stage I to Stage IIIA - the European equivalents of Tier 1 to Tier 3, phased in between 1999 and 2008. Same picture: no aftertreatment.
Tier 4 Interim - the US EPA standard phased in from 2011. Most manufacturers met it with a particulate filter and exhaust gas recirculation. FPT went a different way and used SCR without either, on an earlier engine control unit than the one covered here. The AdBlue system exists on these machines, but it is a different generation and the Lavanis SCR-One does not support it.
Stage IIIB - the European equivalent of Tier 4 Interim, phased in from 2011.
Tier 4 Final - the US EPA standard for non-road diesel engines, phased in from 2014. On FPT engines this is the HI-eSCR architecture: a diesel oxidation catalyst and an SCR catalyst, with a Denoxtronic 2.2 dosing unit and a Bosch EDC17CV41 engine control unit. This is the platform the Lavanis SCR-One is built for. There is no Tier 5; the EPA never enacted one.
Stage IV - the European equivalent of Tier 4 Final, phased in from 2014. Machines built to either standard share the same aftertreatment architecture.
Stage V - the European standard that replaced Stage IV, mandatory from 1 January 2019 for engines over 130 kW and from 1 January 2020 for engines between 56 and 130 kW. Stage V added a particulate filter and moved to a different engine control unit, which is why the build year matters as much as the model. There is no US equivalent.