Subaru Impreza 2003 Service Manual page 1713

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
B: DTC 23 MASS AIR FLOW SIGNAL (TURBO MODEL)
DIAGNOSIS:
The input signal circuit of TCM from ECM is open or shorted.
TROUBLE SYMPTOM:
Excessive shift shock.
WIRING DIAGRAM:
B54
1 2 3 4 7 8
5 6
10 11 12 13 14 15 16 17 18
19 20 21 22 23 24
Step
1 CHECK ENGINE GROUND TERMINALS AND
GROUND CIRCUIT OF ECM.
<Ref. to 4AT-48, DTC 31 THROTTLE POSI-
TION SENSOR, Diagnostic Procedure with
Diagnostic Trouble Code (DTC).>
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ECM.
1)Turn the ignition switch to OFF.
2)Disconnect the connectors from TCM and
ECM.
3)Measure the resistance of harness between
TCM and ECM connector.
Connector & terminal
(B54) No. 1 — (B135) No. 28:
3 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ECM.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B54) No. 1 — Chassis ground:
4 PREPARE SUBARU SELECT MONITOR.
B135
1 2 3 4 5 6 7 8
9
16 17 18 19
10 11 12 13 14 15
20 21 22 23 24 25 26 27 28
AUTOMATIC TRANSMISSION (DIAGNOSTICS)
B135 ECM
B54 TCM
9
Check
Is there any trouble?
Is the resistance less than 1
Ω?
Is the resistance more than 1
MΩ?
Do you have a Subaru Select
Monitor?
4AT-43
Yes
Repair the ground Go to step 2.
terminal and/or
ground circuit of
ECM.
Go to step 3. Repair the open
circuit in harness
between TCM and
ECM connector.
Go to step 4. Repair the short
circuit in harness
between TCM and
ECM connector.
Go to step 6. Go to step 5.
AT-01140
No