Transmission Control Systems

TROUBLE CODE 21
ATF TEMPERATURE SENSOR

Diagnosis
Input signal circuit of Transmission Control Module (TCM) to Automatic Transmission Fluid (ATF) Temperature Sensor is open or shorted.

Trouble Symptom
- Excessive shift shock.
- No lock-up occurs (after Engine warm-up).
- No shift up to 4th speed (after Engine warm-up).





1. Measure signal voltage input of TCM.





a. Turn Ignition Switch "ON" (with Engine "OFF") and measure signal voltage input of TCM.
b. Start and warm-up the Engine. Measure signal voltage input of TCM.

Connector & Terminal / Specified Voltage:
(B53) No. 19 - No. 4 /
2.9 - 4.0 Volts [ATF temperature: 20°C (68°F)]
1.0 - 1.4 Volts [ATF temperature: 80°C (176°F)].

Select Monitor Function Mode.
- Mode: F08 or F07
- Condition:
Warm-up the Engine to increase ATF temperature.
- Specified Data:
ATFT FO8 or F07
(Temperature shown on display increases.)

2. Check harness and connectors between TCM and ATF Temperature Sensor.
a. Disconnect connector from TCM.
b. Disconnect connector from Transmission.





c. Measure resistance between TCM connector and Transmission connector, and between TCM connector and body.

Connector & Terminal / Specified Voltage:
(B53) No. 19 - (B9) No. 5 / 0 Ohms.
(B53) No. 19 - Body / 1 M Ohm, minimum
(B53) No. 4 - (B9) No. 12 / 0 Ohms.

3. Check ATF Temperature Sensor.
a. Disconnect connector from Transmission.
b. Measure resistance between Transmission connector receptacle's terminals.

Connector & Terminal / Specified Resistance:
(T4) No. 5 - No. 12 / 2.1 - 2.9 K Ohms, [ATF temperature: 20°C (68°F)].

c. Connect connector to Transmission, and warm-up the Engine to increase ATF temperature.
d. Stop the Engine and disconnect connector from Transmission.





e. Measure resistance between Transmission connector receptacle's terminals.

Connector & Terminal / Specified Resistance:
(T4) No. 5 - No. 12 / 275 - 375 Ohms, [ATF temperature: 80°C (176°F)].