Subaru Legacy 2003 Service Manual page 1845

ENGINE (DIAGNOSTICS)
3. General Description
A: CAUTION
1) Airbag system wiring harness is routed near the
engine 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 ECM, be sure to turn OFF the ignition
switch.
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 ECM from the located position,
disconnect two cables on the battery.
• Otherwise, the ECM may be damaged.
CAUTION:
When replacing ECM, be careful not to use the
wrong spec. ECM to avoid any damage on 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.
GENERAL DESCRIPTION
8) Use ECM or TCM mounting stud bolts at the
body head grounding point when measuring the
voltage and resistance inside the passenger com-
partment.
9) Use engine grounding terminal or engine proper
as grounding point to the body when measuring the
voltage and resistance in the engine compartment.
10) Every MFI-related part is a precision part. Do
not drop them.
EN(H4DOSTC)-6
( A )
(A) Stud bolt
( A )
EN-00001
EN-00154
EN-00952