Transmission

P0743 — Torque Converter Clutch Circuit Electrical Fault

Severity: medium Drive with care, to a shop

What P0743 means

P0743 means the transmission control module (or engine computer) detected an electrical problem in the torque converter clutch (TCC) solenoid circuit. Normally the module energizes the solenoid at cruising speed so the clutch locks the converter, removing slip and saving fuel. An open, short or wrong voltage in the circuit prevents lockup.

Symptoms

  • Check engine or transmission warning light on
  • No torque converter lockup at highway speed
  • Higher fuel consumption
  • Engine RPM higher than normal while cruising
  • Overheated transmission fluid
  • Shudder or surging when lockup tries to engage

Possible causes

  1. Failed TCC solenoid
  2. Damaged wiring or corroded pins in the transmission connector
  3. Open circuit or short to ground or power in the solenoid circuit
  4. Faulty driver inside the TCM or PCM
  5. Fluid leaking into the connector or contaminated transmission fluid
  6. Internal valve body problem

How to diagnose

  1. Scan all codes and freeze frame data, clear the code and see if it returns
  2. Check transmission fluid level and condition
  3. Inspect the transmission harness and connector for corrosion, oil, chafing and bad locks
  4. Measure TCC solenoid resistance and compare it with the manufacturer spec
  5. Test the circuit for opens, shorts to ground and shorts to power
  6. Check supply voltage and the control signal from the module at the connector
  7. Command the solenoid with a scan tool and watch the response
  8. If solenoid and wiring are good, test the control module

Common fixes

  • Replace the TCC solenoid
  • Repair the wiring harness or replace the damaged connector
  • Change transmission fluid and filter if contaminated
  • Replace or reprogram the transmission control module
  • Repair the valve body if there is an internal fault

Questions and answers

Can I drive with a P0743 code?

For a short time, yes, but lockup will not work, so fuel use and fluid temperature rise. Do not put off the repair.

What most often causes P0743?

Usually a failed TCC solenoid or a wiring or connector problem at the transmission. The control module is a less common cause and is checked last.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.