Transmission Control Systems

TROUBLE CODE 21: ATF TEMPERATURE SENSOR

DIAGNOSIS:
Input signal circuit of TCM to ATF temperature sensor is open or shorted.

TROUBLE SYMPTOM:
Excessive shift shock





FLOW CHART





WIRING DIAGRAM

1. CHECK HARNESS AND CONNECTORS BETWEEN TCM AND ATF TEMPERATURE SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connectors from TCM and transmission.
3) Measure resistance of harness connector between TCM and transmission connector.





Connector & terminal / Specified voltage:
(B96) No. 10 - (B9) No. 5 / 1 ohms, or less
(B53) No. 20 - (B9) No. 12 / 1 ohms, or less

4) Measure resistance of harness connector between TCM and body to make sure that circuit does not short.





Connector & terminals / Specified resistance:
(B96) No. 10 - Body / 1 Mohms, or more
(B53) No. 20 - Body / 1 Mohms or more

2. CHECK ATF TEMPERATURE SENSOR.
1) Measure resistance between transmission connector receptacle's terminals.





Connector & terminal / Specified resistance:
(T4) No. 5 - No. 12 /
2.1 - 2.9 kohms [ATF temperature: 20 deg C (68 deg F)]

2) Connect connectors to transmission and TCM.
3) Start and warm-up the engine until AIF temperature has increased.
4) Stop the engine and disconnect connector from transmission.
5) Measure resistance between transmission connector receptacle's terminals.





Connector & terminal / Specified resistance:
(T4) No. 5 - No. 12 /
275 - 375 ohms [ATF temperature: 80 deg C (176 deg F)]

3. CHECK INPUT SIGNAL FOR TCM.
1) Turn ignition switch ON (with engine OFF) and measure signal voltage input of TCM.
2) Start and warm-up the engine. Measure signal voltage input of TCM.





Connector & terminal / Specified voltage:
(B96) No. 10 - (B53) No. 20 /
3.45±0.55 V [ATF temperature: 20 deg C (68 deg F)]
1.2±0.2 V [ATF temperature: 80 deg C (176 deg F)]

- Using Subaru select monitor:
(1) Turn ignition switch to OFF.





(2) Connect the Subaru select monitor to data link connector.
(3) Turn ignition switch to ON and Subaru select monitor switch to ON.
(4) Start and warm-up the engine.
(5) Read data on Subaru select monitor.
(6) Designate mode using function key.

Function mode: F07 or F08

SPECIFIED DATA:





F07:
- Ambient temperature: ±50 deg F
- ATF temperature: 158 - 230 deg F
- Open harness: 176 deg F
- Shorted harness: 320 deg F





F08:
- Ambient temperature: ±10 deg C
- ATF temperature: 70 - 110 deg C
- Open harness: 80 deg C
- Shorted harness: 160 deg C
- F07: ATF temperature is indicated in "deg F".
- F08; ATF temperature is indicated in "deg C".