PREVOST X3-45 Multiplex, Maintenance Manual

Page: 52 / 1422

Section 01: ENGINE
PA1562
22
problem solving in the form of a code. The MCM
and CPC continuously perform self diagnostic
checks and monitor the other system
components. Information for problem
identification and problem solving is enhanced
by the detection of faults, retention of fault codes
and separation of active from inactive codes.
The engine-mounted MCM includes control logic
to provide overall engine management. System
diagnostic checks are made at ignition on and
continue throughout all engine operating modes.
Sensors provide information to the MCM and
CPC regarding various engine and vehicle
performance characteristics. The information is
used to regulate engine and vehicle
performance, provide diagnostic information,
and activate the engine protection system.
The DDEC VI on-board diagnostic system
accessories include the following:
•
Check Engine telltale light (AWL);
•
Stop Engine telltale light (RSL);
•
Stop Engine Override switch (SEO);
•
Diagnostic Data Link (DDL) connectors.
The AWL is illuminated and a code is stored if
an electronic system fault occurs. This indicates
the problem should be diagnosed as soon as
possible. The CPC illuminates the AWL and
RSL and stores a malfunction code if a
potentially engine damaging fault is detected.
These codes can be accessed in one of four
ways:
•
Commercially available J1587/J1939
diagnostic tools.
•
Detroit Diesel Diagnostic Link® (DDDL 7.0).
•
Flashing the AWL and RSL with the
SEO/Diagnostic Request Switch.
•
Dashboard’s Message Center Display
(MCD).
2.8.2 Check Engine Telltale Light (AWL)
The CPC illuminates the Check Engine telltale,
mounted on the telltale light panel to indicate
that a problem has been detected and that a
code has been stored in the MCM memory.
This light also has a 5-second bulb check when
the ignition is first turned on.
2.8.3 Stop Engine Warning Light (RSL)
This light, also mounted on the telltale light
panel, illuminates to indicate that a major engine
problem is occurring (with the exception of a 5-
second bulb check when the ignition is first
turned on).
2.8.4 Stop Engine Override Switch (SEO)
This switch, mounted on the dashboard, may be
used to extend the 30-second delay period
before engine shutdown when the Stop engine
telltale light is illuminated. This switch can be
repeatedly depressed in order to move the
vehicle out of traffic.
NOTE
The stop engine override switch will be
operative only if it has been depressed before
the end of the 30 second delay period.
CAUTION
The OVERRIDE switch must be used only in
emergency cases, such as to move the
vehicle out of traffic. Excessive use of this
switch can cause serious damage to the
engine.
This switch is also used for DDEC diagnostic
code requests. Press this switch with the engine
at idle or off but with the ignition in the "ON"
position and active codes will be flashed on the
CHECK ENGINE and STOP ENGINE telltale
lights alternately.
2.8.5 Diagnostic Data Link (DDL) Connectors
A connector is mounted on the L.H. footwell
wall. Another connector is located in the rear
electric compartment. They allow the connection
of the Diagnostic Data Reader (DDR) to read
the codes or to access pertinent data on the
condition of the engine. This enables a more
complete analysis of any defect found in the
DDEC system operation. For more information,
see Detroit Diesel Troubleshooting Guide
#6SE492.
2.9 READING DIAGNOSTIC CODES –
FLASHING LIGHT METHOD:
DDEC VI makes use of two types of codes:
Active and inactive. The difference between the
two types of codes is as follows: