P0743 code - Theory TCC solenoid is activated when the transmission control module (TCM) determines that the torque converter cluth should be actived. The torque converter clutch is a variable slip torque clutch that allows control of the slip from 5.5 % of lock up. The torque converter is a vailable slip torque clutch that allows control of the slip from 5.5% to 95.5% of lock up. The clutch is controlled by the TCC solenoid which is pulse width modulated (PWM) to provide the desired amount of slip. The clutch requires both an electronical PWM of 1000 Hz and an hydrulic PWM of 100Hz.

When monitored this DTC continuously with the ignition on, engine running, with the transmission in gear, the TCC solenoid is inactive, or when the TCC solenoid is active and controlled above 25% duty cycle, with the solenoid supply votage active. Set condition this DTC if the TCM detects on the TCC solenoid control circuit : open, short to ground, short to voltage, internal short in the TCC solenoid or an open in the TCC solenoid.

Possible causes P0743 code :

- TCC solenoid contro circuit open

- TCC solenoid control circuit shorted to ground

- TCC solenoid control circuit for a shorted to another circuit

- TCC solenoid

- Transmission control module (TCM)

Diagnostic test P0743 code

Step 1. Check if the DTC is current

If the TCM detects and stores a DTC, the TCM also store the vehicles operating conditions under which the DTC originally set. This information is located in scan tool environmental data. Before erasing any stored DTCs, record any available data to assist in duplicating the conditions in which the DTC originally set.

Turn the ignition off to the lock position. With the scan tool, erase transmission DTCs. Using the environmental data recorded earlier, try to duplicated the conditions in which the DTC originally set. It may be necessary to test drive the vehicle. With the scan tool, read transmission DTCs.

Did the DTC P0743 reset ?

Yes, go to step 2.

No, go to step 6.

Step 2. Check the TCC solenoid control circuit for an open

Turn the ignition off to the lock position. Disconect the TCM C2 harness connector. Disonect the transmission electrohydraulic control unit assembly harness connector. Check connectors clean/repair as necessary.

Measure the resistance of the TCC solenoid control circuit from the TCM C2 harness connector to the transmission electrohydraulic control unit assembly harness connector.

Is the resistance below 5.0 Ohm ?

Yes, repair the TCC solenoid control circuit for an open.

No, go to step 3.

Step 3. Check the TCC solenoid control circuit for a short to ground

Measure the resistance between ground and the TCC solenoid control circuit.

Is the resistance below 5.0 Ohms ?

Yes, repair the TCC solenoid control circuit for a short to ground.

No, go to step 4.

Step 4. Check the TCC solenoid control circuit for a short to another circuit

Measure the resistance between the TCC solenoid control circuit and all other circuits in the transmission electrohydraulic control unit assembly harness connector.

Is the resistance below 5.0 Ohms between the TCC solenoid control circuit and any other circuit(s) in the transmission electrohydraulic control unit assembly harness connector?

Yes, repair the TCC solenoid control circuit for a short to another circuit.

No, go to step 5.

Step 5. Check the TCC solenoid resistance

Disconnect the transmission electrohydraulic control unit assembly harness connector. Measure the resistance of the TCC solenoid between 2.0 and 4.0 Ohms?

Is the resistance of the TCC solenoid between 2.0 and 4.0 Ohms ?

Yes, using the schematics as a guide, check the transmission control module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM in accordance with the service information.

No, replace the TCC Solenoid.

Step 6. Check the wiring and connectors

The conditions necessary to set this DTC are not present at this time. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit. Wiggle the wiring and connectors while checking for any possible open or shorted circuits. Check for any service information tune-ups or technical service bulletins that may apply.

Were there any problems found?

Yes, repair as necesssary. Perform NAG1 Transmission Verification Test.

No, test complete.

P0743 TCC solenoid circuit