Subaru Legacy 2003 Service Manual page 25

DIAGNOSTIC PROCEDURE WITH TROUBLE CODE (DTC)
C: DTC P1574 KEY COMMUNICATION FAILURE
DIAGNOSIS:
• Failure of IMM ECM to verify key (transponder) ID code
1 CHECK IMM ECM FUNCTION.
Insert the key to ignition switch (LOCK posi-
tion), measure changes in voltage between
antenna connector terminals.
Connector & terminal
(B142) No. 1 (+) — No. 2 ( − − − − ):
Is the measured value same as the specified
value?
2 CHECK IGNITION KEY (TRANSPONDER).
1) Remove the key from ignition switch.
2) Start engine using other keys that have
undergone the teaching operation, fur-
nished with vehicle.
Does engine start?
Step Value
−30 to 30 V (Approximately 0.1
second after inserting the key.)
0 V (Approximately 1 second
after inserting the key.)
Engine starts.
IM-23
IMMOBILIZER (DIAGNOSTICS)
Yes
Go to step 2. Replace IMM ECM
<Ref. to SL-36,
Immobilizer Con-
trol Module.> and
then replace all
ignition keys
(including the tran-
sponder). Then
perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).
Replace ignition Replace IMM ECM
key (including the <Ref. to SL-36,
transponder). Immobilizer Con-
Then perform trol Module.> and
teaching opera- then replace all
tion. Refer to ignition keys
teaching opera- (including the tran-
tion manual (Pub. sponder). Then
No. S0820GZ). perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).
No