The P0743 code in your 2022 Toyota Highlander indicates an electrical problem in the torque converter clutch solenoid circuit. Unlike codes that describe TCC behavior (stuck on/off), P0743 specifically identifies an electrical issue—a short, open, or improper resistance in the circuit controlling the TCC solenoid.
Electrical Circuit Issues
The TCC solenoid circuit includes the solenoid coil itself, wiring from the TCM to the solenoid, and the transmission connector. P0743 triggers when the TCM detects abnormal electrical characteristics—perhaps no current flow (open), excessive current (short), or resistance outside specifications.
Common Causes
A failed TCC solenoid with an open or shorted coil is common. Damaged wiring between the TCM and transmission connector creates circuit faults. Corroded transmission connector pins affect circuit integrity. Poor grounds at the transmission or TCM affect current flow. Water intrusion into connectors causes electrical problems.
Symptoms in Your Highlander
TCC may not function at all, similar to P0740 symptoms—reduced fuel economy and higher transmission temperatures. Alternatively, TCC may behave erratically. The check engine light illuminates with P0743 stored. Other transmission operation may be normal if only the TCC circuit is affected.
Toyota Diagnostic Approach
Using Toyota Techstream, check TCC solenoid resistance against specifications. Measure at the transmission connector to test wiring as well as the solenoid. Check for proper voltage at the solenoid when TCC is commanded. Inspect the transmission connector for damage or corrosion. Test for shorts to ground and opens in the circuit.