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DTC P0743 TORQUE CONVERTER CLUTCH CIRCUIT ELECTRICAL

DTC P0743 TORQUE CONVERTER CLUTCH CIRCUIT ELECTRICAL

DIAGNOSIS:

The output signal circuit of lock-up duty solenoid is open or shorted.

TROUBLE SYMPTOM:

No “lock-up” (after engine warm-up).

WIRING DIAGRAM:


CHECK DTC.

Do multiple DTCs appear in the on-board diagnostics test mode?

Yes

Go to another DTC.


No


CHECK HARNESS CONNECTOR BETWEEN TCM AND TRANSMISSION.

Turn the ignition switch to OFF.

Disconnect the connector from TCM and transmission.

Measure the resistance of harness between TCM and transmission connector.

Connector & terminal

(B56) No. 5 — (B11) No. 12:

Is the resistance less than 1 Ω?

Yes


No

Repair the open circuit in harness between TCM and transmission connector.


CHECK HARNESS CONNECTOR BETWEEN TCM AND TRANSMISSION.

Measure the resistance of harness connector between TCM and chassis ground.

Connector & terminal

(B56) No. 5 — Chassis ground:

Is the resistance more than 1 MΩ?

Yes


No

Repair the short circuit in harness between TCM and transmission connector.


CHECK LOCK-UP DUTY SOLENOID.

Measure the resistance between transmission connector receptacle’s terminals.

Connector & terminal

(T4) No. 12 — No. 20:

Is the resistance 2.0 — 6.0 Ω?

Yes


No


CHECK LOCK-UP DUTY SOLENOID (IN TRANSMISSION).

Disconnect the transmission connector.

Drain the ATF.

Important

Do not drain the ATF until it cools down.


Remove the oil pan and disconnect connector from lock-up duty solenoid.

Measure the resistance between lock-up duty solenoid and transmission ground.

Connector & terminal

(AT12) No. 4 — Transmission ground:

Is the resistance 2.0 — 6.0 Ω?

Yes


No

Replace the control valve body.


CHECK HARNESS CONNECTOR BETWEEN LOCK-UP DUTY SOLENOID AND TRANSMISSION.

Measure the resistance of harness between lock-up duty solenoid and transmission connector.

Connector & terminal

(T4) No. 12 — (AT12) No. 4:

Is the resistance less than 1 Ω?

Yes


No

Repair the open circuit in harness between TCM and transmission connector.


CHECK HARNESS CONNECTOR BETWEEN LOCK-UP DUTY SOLENOID AND TRANSMISSION.

Measure the resistance of harness between transmission connector and transmission ground.

Connector & terminal

(T4) No. 12 — Transmission ground:

Is the resistance more than 1 MΩ?

Yes

Even if the POWER indicator blinks, the circuit has returned to a normal condition at this time. A temporary poor contact of the connector or harness may be the cause. Repair the harness or connector in lock-up duty solenoid and transmission.


No

Repair the short circuit in harness between lock-up duty solenoid and transmission connector.