Introduction
Term(s) Abbreviation Definition
(if applicable) Previously
used term(s) (or Eng-
lish Equivalent)
downshift
draft _.
drivability
driveshaft
driveshaft tunnel
dry sleeve
Dual Overhead Cam
Data
Data Link Connector
Data Output Line
defogger, backlight defogger
degree (angle or temperature)
Department of Transportation
(US)
Department of Transport (UK)
Deutsche lnstitut fur
Normuna
diameter
Diagnostic Module
Diagnostic Test Mode
Diagnostic Trouble Code
differential housing
differentia
I pressure
Differential Pressure Feedback
EGR
dimmer switch DOHC
DLC
DOL
deg, O
DOT
DTP DIN dia
DM
DTM
DTC
DPFE longitudinal
shaft transmitting power from
transmission output to rear axle differential
tunnel
in floor above the driveshaft (propeller
shaft)
cylinder sleeve which is not in contact with
coolant
engine configuration with two camshafts
positioned above the valves
(US) Fact or group of facts.
connector providing access
andlor control of
the vehicle information, operating
conditions, and diagnostic information
circuit that sends certain information from
the PCM to the instrument cluster
German Standards regulation body
Supplemental Restraint System
(non-controlling) module for diagnostics
overview
a level of capability in an OBD system. May
include different functional states
to observe
signals, a base level to read
DTCs, a monitor
level which includes information on signal
levels,
bi-directional control with onloff board aids, and the ability to interface with
remote diagnosis
an
alphahumeric identifier for a fault
condition identified by the On
-Board
Diagnostic
(OBD) system
rotating housing
(in a bevel differential)
attached to the crownwheel, carrying the
final drive pinions
pressure difference between two regions e.g.
between intake manifold and atmospheric
pressures
an EGR system that monitors differential
EGR pressure across a remote orifice
to control EGR flow change
down
draught
driveability
propeller shaft
transmission
tunnel
dry liner
(English) Group
of facts (i.e. plural
of
datum)
HRW, rear screen
heater, demister
Self Test Mode
Self Test Code.
Fuel Fail code
differential cage
dip switch,
dipper switch
Issue 1 August 1994 11 X300 VSM
12.1.5. ABS Components
Hydraulic Module
The hydraulic module is located under the bonnet adjacent
to the engine compartment firewall. It is secured within a steel mounting bracket at three securing points. All elec- tronic and power connections are made through one cable
loom connect ion.
The hydraulic pump
(1 Fig. 1) is a reciprocating two-circuit pump in which one brake circuit is assigned to each pump
circuit. The pump supplies adequate pressure and volume
supply to the brake circuits under anti
-lock braking condi- tions. The pump is driven by and electric motor (2 Fig. 1). The
pump housing incorporates two low pressure accumulators
and damping chambers for each brake circuit.
A modulator valve block
(3 Fig. 1) incorporates the ABS CM or ABS / TC CM (4 Fig. 1). Vehicles with traction control are
fitted with a throttle position actuator (5 Fig. I), which is an
electrical device controlled by the ABS 1 TC CM.
Valve blocks on vehicles without traction control comprise
six solenoid valves, three normally open (NO) inlet valves
and three normally closed
(NC) outlet valves. These valve
blocks have three outlet ports. Valve blocks on vehicles with
traction control comprise nine solenoid valves, four
NO inlet valves,four NC outlet valves and one special isolating valve.
Fig. 2 shows a hydraulic module for vehicles with traction
control. The valve block (2 Fig. 2) has four outlet ports (Indi- vidual control of the driven wheels).
A BS CM, A BS / TC CM
The ABS CM or ABS TCI CM locates beneath the modulator
valve block and is secured by
two screws. The CM houses
the solenoids which operate the inlet and outletvalves of the
modulator valve block. When fitted, the valve stems locate
in the
CM mounted solenoids. There is no electrical connec- tion between the CM and the modulator valve block. Fig. 3 shows an ABS TC 1 CM having nine solenoids.
The
CM functions include the following:
0 Providing control signals for the operation of ABS
and traction control solenoid valves
0 Calculating wheel speed from voltage signals trans- mitted by the wheel speed sensors
0 Monitoring of all electrical components
0 On Board Diagnostics (OBD): storage of possible fail- ures in a non-volatile memory.
The signals from the four wheel speed sensors are indepen
- dently processed by the ABS CM or ABSITC CM, calculating
numerical values which correspond directly to the wheel
speed. These values are converted into control signals for
pressure modulation during ABS control.
The ABS and traction control
are continuously monitored,
whilst the ignition is on,for possiblefaults and interruptions.
If a fault is detected, the module deactivates the ABS and
indicates this by lighting the ABS warning lamp. In a fault
condition, conventional braking is unaffected. The module
stores fault codes in a non
-volatile memory which can be
read via the OBD link.
U: For electrical diagnostic information on the ABS I traction control systems, refer to EDM, Section 12. Fia.
1
Fia. 2
Fin. 3 I
J70286
Issue 1 August 1994 X300 VSM
