POWER TRAIN MLC80A-1/MLC90A-1/MLC100A-1/MLC100-1 SERVICE/MAINTENANCE MANUAL
7-16
Published 10-09-2020, Control # 259-06
The DEF supply module is heated electrically and with
engine coolant. It has a 10-micron filter that requires periodic
cleaning and inspection. For filter maintenance intervals,
refer to the engine manufacturer’s manual.
Coolant Control Valve
When needed, the DEF is heated by engine coolant, which is
circulated through a heat exchanger in the tank. If the tank
temperature drops below –4°C (25°F), the ECM opens the
coolant control valve (3) to allow coolant to flow through the
heat exchanger and the DEF supply module.
DOC/DPF Module
The DOC/DPF module (4) oxidizes the remaining
hydrocarbons in the exhaust to carbon dioxide. It
incorporates an NO
x
sensor, a dP sensor, and two
temperature sensors.
The DOC/DPF should be sent to the engine manufacturer for
cleaning or exchanged for a clean one at a minimum service
interval of 4,500 heavy-duty operating hours (roughly every 2
years of one-shift operation).
NOTE: DPF cleaning requires special tools and equipment
and should not be attempted by field service
personnel.
DEF Dosing Module
The DEF dosing module (5) injects a liquid mixture of urea
and deionized water (called DEF) into the exhaust stream
ahead of the inlet to the SCR module (6). The flow of DEF
through the dosing module also keeps it cool and operable.
SCR Module
The SCR module (6) incorporates a catalyst, two
temperature sensors, an NH
3
sensor, and an NO
x
sensor.
The SCR module utilizes DEF (urea and deionized water) to
reduce NO
x
content in the exhaust gas to nitrogen.
The SCR module does not require maintenance.
Excessive NO
x
Warning System
If an excessive NO
x
warning is issued, check anything that
might cause an elevated NO
x
level, such as:
• Disconnected DEF tank level or quality sensor
• Blocked DEF hose or dosing module
• Disconnected dosing module
• Disconnected supply module
• Disconnected SCR wiring harness
• Disconnected NO
x
sensor
APS
The APS continually monitors exhaust gas temperatures. In
the event of excessive exhaust temperatures, the APS
activates the HEST icon on the main display.
DRP
The DRP (7) is a pipe mounted between the DOC/DPF
module (4) and the SCR module (6).
The DRP does not require maintenance.
WARNING
Personal Injury or Equipment Damage Hazard!
Do not remove hoses from or attempt to service the DEF
supply module without first consulting the engine
manufacturer’s instructions. Personal injury and/or
equipment damage may result.
CAUTION
Use Only Approved Replacement Parts!
The DEF system components are designed to withstand
freezing and to be compatible with DEF and the other
unique characteristics of the system. Use of non-
approved replacement parts may result in system
damage.
CAUTION
Loss of Power or Engine Shutdown Hazard!
If NO
x
emissions exceed legislated limits, the operator is
alerted by warning lights and audible warnings. If the
condition is not corrected in a set amount of time, an
engine derate and shutdown sequence begins.
Refer to the Main Display Operation Manual for
identification and location of the engine and exhaust
aftertreatment warning lights.
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