P0743

P0743 is an electrical fault on the torque converter clutch solenoid circuit, meaning the TCM commanded the TCC solenoid and saw open circuit, short to ground, or short to power based on the feedback voltage on the driver. Cheapest-first ladder: measure solenoid resistance at the case connector (typical spec 10-15 ohms for PWM TCC, 20-30 ohms for on/off depending on platform) and compare to the FSM; back-probe the TCM-side circuit for continuity and proper ground reference with the connector unplugged; inspect the internal wire harness/pass-through connector inside the pan for fluid-saturated insulation and corroded pins (the #1 root cause on many late-model GM and Ford units); only then condemn the solenoid itself. Caveat: do not confuse P0743 (electrical) with P0741 (performance/slip) — they call out different failure modes and a P0743 will not be cured by a torque converter replacement.

Vehicle-specific patterns: 1996-2005 Chevrolet/GMC trucks with the 4L60E and 4L80E set P0743 from internal harness pass-through connector pin corrosion at case connector D. 2007-2013 Dodge Ram with the 545RFE and 65RFE set P0743 when the internal harness chafes against the valve body. 2004-2010 Ford F-150 with the 5R110W TorqShift sets P0743 from a failed internal wiring harness. 2008-2014 Cadillac CTS and 2010-2015 Camaro with the 6L50/6L80 set P0743 alongside a TCC slip code when the TCC PWM solenoid sticks from valve body wear, addressable with a Sonnax TCC regulator valve and sleeve kit. Estimated repair: $180 to $1,400.