Troubleshooting T4i engines with high NOx values
Sulphur poisoning
If this is the root cause, the fault code is often generated alone, without
other related fault codes in EMS S8 or in EEC3. Sulphur poisoning is
not visible, but reduces the conversion rate of the catalytic converter
and thereby leads to increased NOx values. Before continued trouble-
shooting is started, a refractometer must be used to ensure that the
reductant is of good quality. Also check that there are no large accu-
mulations of crystallised reductant in the catalytic converter. If there
is extensive crystallisation in the exhaust system, make sure that the
engine is equipped with an evaporator and not hydrolysis. See RA 11
03 13 for more information. To ensure that crystallisation is not caused
by a leaking doser, the doser should be leak tested using SDP3.
The risk of sulphur poisoning and thereby NOx related fault codes
increases dramatically for machines operating with low loads or in
extremely low ambient temperatures. To keep the exhaust gas after-
treatment system in good condition and thereby avoid such problems,
it is vital to only use good quality diesel. Use diesel with a maximum
sulphur content of 10 ppm in Europe and 15 ppm in the USA. It has
been shown that some end customers have poor knowledge of fuel
quality requirements for Tier4i and Tier4 Final engines.
Service solution
For DA30: The service solution is based on using restriction washer
and locking pliers to temporarily increase the exhaust gas temperature
and thereby burn away sulphur residue from the catalytic converter.
Contact your distributor to order a restriction washer. Once
this procedure is complete, the original efficiency of the catalytic
converter will be restored and the fault code can then be deleted with
SDP3.
Engine
SHOP MANUAL
Ch 1 page 225
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