P0743: Torque Converter Clutch Circuit Electrical

What does P0743 mean?

Common causes

• Corroded or unlatched pins in the transmission connector, checked before the pan comes off
• An open or a short in the clutch control wire, which is the first measurement on the Crossfire NAG1 chart
• A converter-clutch solenoid winding outside the resistance band in this transmission's chart
• The valve-body harness, which TSB 23-AT-003H-1 replaces together with the solenoid on the 8-speed vehicles it lists
• A module driver, after the wire and the coil match the chart
• Fluid left in the connector, recorded as a cause of terminal corrosion rather than as an electrical repair by itself

Symptoms

• Check engine light with P0743 stored
• No converter lockup, so engine speed stays high at cruise
• Highway fuel use higher than it was, with the converter slipping
• The transmission still shifts through its gears
• The code returns as soon as the circuit test runs, rather than only when hot or only on bumps
• A harsh feeling when lockup never happens

Diagnostic steps

1. 1.Scan the companion codes. P0741 is a slip test. P0742 may be stuck applied, or a short to ground, depending on the chart. P0743 is the electrical member. Confirm that split in this manual. Ford's 6F35 groups several of these numbers in one pinpoint.
2. 2.Ignition off. Inspect the transmission connector for fluid, corrosion, and terminals that are not latched. It is outside the pan. Reseat it and rerun the circuit test before ordering a solenoid.
3. 3.With both the module connector and the transmission connector unplugged, check the control wire for an open and for shorts to ground and to neighboring circuits. Then reconnect only the transmission connector and measure the solenoid from the module-connector end, the way the Crossfire NAG1 chart does. Compare the reading with this chart. The Crossfire 2.0–4.0 ohm band is for that solenoid.
4. 4.On the 8-speed vehicles in Hyundai/Kia TSB 23-AT-003H-1, follow that bulletin: scan output, external harness, then the solenoid and the valve-body harness together, then the control harness, then the module. Do not skip to a transmission replacement.
5. 5.Command the solenoid with a scan tool only if this procedure says to, key on, engine off, and watch the circuit. A Ford 6F35 wiggle test exists inside that pinpoint. It is a step in that procedure, not a reason to rank the connector above the coil.
6. 6.A fluid service does not close an open wire. If the solenoid replacement requires the pan, support the vehicle on a lift or stands and let the fluid cool before the pan comes off.
7. 7.Clear the code and confirm the circuit test passes, then confirm from a recorded drive that lockup occurs when it is commanded. A passenger reads the tool if anyone is watching it on the road.

Repair cost

$300 – $900 (simple solenoid replacement)

AutoZone prices a simple solenoid replacement at $300–$900, parts and labor, in 'Bad Torque Converter vs Bad Transmission.' That is the printed pair. The article's rebuild band is $1,800–$3,500 and its replacement band is $4,000–$8,000. Neither is this repair. No national parts-and-labor total was found for a connector or pigtail repair, so that job is not given a dollar figure. RepairPal's transmission fluid change, updated 3 September 2026, averages $294–$356 and is the fluid that goes back in when the pan is dropped, not a fix for an open circuit.

DIY vs shop

Leave this one to a qualified shop. The barrier here is internal hydraulic and mechanical work, fluid handling at temperature, and an adaptive relearn afterwards without which a correct repair still shifts badly. DIY attempts often produce a more expensive problem than the original code.

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