Subaru forester 2004 Service Manual page 21

Diagnostics Procedure with Diagnostic Trouble Code (DTC)
C: DTC P1574 KEY COMMUNICATION FAILURE
DIAGNOSIS:
Failure of IMM ECM to verify key (transponder) ID code
Step
1 CHECK IMM ECM FUNCTION.
Insert the key to ignition switch (LOCK posi-
tion), measure changes in voltage between
Antenna connector.
Connector & terminal
(B142) No. 1 (+) — No. 2: (
2 CHECK IGNITION KEY (TRANSPONDER).
1) Remove the key from ignition switch.
2) Start the engine using other keys that have
undergone the teaching operation, furnished
with vehicle.
Is the voltage −30 to 30 V?
(Approx. 0.1 second after
inserting the key)
Is the voltage 0 V?
(Approx. 1 second after insert-
−
) ing the key)
Does the engine start?
IM-19
IMMOBILIZER (DIAGNOSTIC)
Check
Go to step 2.
Replace the igni-
tion key (including
the transponder).
Then perform
teaching opera-
tion. Refer to the
teaching opera-
tion manual (Pub.
No. S0820GZ).
Yes No
Replace the IMM
ECM <Ref. to SL-
37, Immobilizer
Control Module.>
and then replace
all ignition keys
(including the tran-
sponder). Then
perform teaching
operation. Refer to
the teaching oper-
ation manual (Pub.
No. S0820GZ).
Replace the IMM
ECM <Ref. to SL-
37, Immobilizer
Control Module.>
and then replace
all ignition keys
(including the tran-
sponder). Then
perform teaching
operation. Refer to
the teaching oper-
ation manual (Pub.
No. S0820GZ).