Engine
SHOP MANUAL
Ch 1 page 227
The SCR system is unable to build pressure
If this is the reason for the NOx fault code, then fault code DT-
C20E8, required reductant pressure cannot be buildt and main-
tained, will also be found in control unit EEC3. To correct this prob-
lem: carry out a system test in SDP3 and use the troubleshooting
guide below.
The most common reasons for this fault code are reported below.
1. Blocked prefilter in SCR pump
Cause
Grease and dirt have blocked the filter.
Solution
Clean or renew the prefilter that sits inside the pump intake. Un-
screw the union to access the filter. Never use grease to fit hoses
in the SCR system. Only soapy water is permitted to facilitate
fitting of hoses.
If the lter is blocked by vaseline or parafn wax, it may be dif-
cult to se the contamination with the naked eye.
2. Seizing check valves in the SCR pump
Cause
If an SCR pump has not been used for a long preiod of time, the
check valves could seize and become jammed due to crystallised
urea in the valves. This could also be a problem on new spare
part pumps that have spent a long time in stock. Nowdays reduct-
ant with an extremly low concentration is used when testing these
pumps in production. Reductant with low concentration reduces
the risk of this problem occurring. Nonetheless, local stocks may
still have the old pumps.
Solution
Pressurise the intake (suction side) of the SCR pump for 3 sec-
onds with compressed air 6-10 bar. The suction side of the pump
is marked “IN”. Always carry out this procedure before fitting a
spare part pump.
NOTE
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