Subaru Impreza 2003, Service Manual

Page: 782 / 3610

EN(H4SOw/oOBD)-6
ENGINE (DIAGNOSTICS)
GENERAL DESCRIPTION
3. General Description
A: CAUTION
1) Airbag system wiring harness is routed near en-
gine control module (ECM), main relay and fuel
pump relay.
CAUTION:
• All airbag system wiring harness and con-
nectors are colored yellow. Do not use electri-
cal test equipment on these circuit.
• Be careful not to damage the airbag system
wiring harness when servicing the engine con-
trol module (ECM), transmission control mod-
ule (TCM), main relay and fuel pump relay.
2) Never connect the battery in reverse polarity.
• The ECM will be destroyed instantly.
• The fuel injector and other part will be damaged
in just a few minutes more.
3) Do not disconnect the battery cables while the
engine is running.
• A large counter electromotive force will be gener-
ated in the alternator, and this voltage may damage
electronic parts such as ECM, etc.
4) Before disconnecting the connectors of each
sensor and the ECM, be sure to turn the ignition
switch to OFF.
5) Poor contact has been identified as a primary
cause of this problem. To measure the voltage and/
or resistance of individual sensors or all electrical
control modules at the harness side connector, use
a tapered pin with a diameter of less than 0.64 mm
(0.025 in). Do not insert the pin more than 5 mm
(0.20 in) into the part.
6) Before removing the ECM from located position,
disconnect two cables on battery.
• Otherwise, the ECM may be damaged.
CAUTION:
When replacing the ECM, be careful not to use
the wrong spec. ECM to avoid any damage on
the fuel injection system.
7) The connectors to each sensor in the engine
compartment and the harness connectors on the
engine side and body side are all designed to be
waterproof. However, it is still necessary to take
care not to allow water to get into the connectors
when washing the vehicle, or when servicing the
vehicle on a rainy day.
8) Use the ECM mounting stud bolt at the body
head grounding points when measuring voltage
and resistance inside the passenger compartment.
9) Use the engine grounding terminal or engine
proper as the grounding point to the body, when
measuring voltage and resistance in the engine
compartment.
10) Use the TCM mounting stud bolts at the body
head grounding point, when measuring voltage and
resistance inside the passenger compartment.
11) Every MFI-related part is a precision part. Do
not drop them.
(A) Stud bolt
(A) Stud bolt
EN-00001
(A)
EN-00153
EN-00154
(A)