Faulty torque converter clutch (lockup) solenoid (both sources). Wiring or circuit shorted to power or ground (OBD-Codes.com). Low or dirty transmission fluid; RepairPal says dirty fluid can restrict hydraulic passages (both sources). Worn or failed clutch assembly inside the torque converter (both sources). Faulty valve body or engine coolant temperature sensor (RepairPal). Faulty PCM/ECM (OBD-Codes.com, which treats it as a last resort). The sources differ: OBD-Codes.com treats P0743 as an electrical circuit fault, while RepairPal frames it as the converter failing to lock and lists hydraulic and mechanical causes too.

Repair wiring or connectors shorted to power or ground. Replace a faulty TCC solenoid, after checking it for debris (OBD-Codes.com found metallic debris on the solenoid caused it in the author's case). Change transmission fluid and filter if the fluid is low or dirty. Repair the valve body or replace the torque converter if testing shows the clutch isn't locking. Reprogram or replace the PCM only after wiring and solenoid tests pass; a replacement must be programmed to the vehicle.

P0743🔧 Transmission / Torque converter clutchDrive with caution, fix soon

P0743: Torque Converter Clutch Circuit Electrical (Meaning, Causes, Fixes)

Q: What does P0743 mean?

P0743 means the computer found an electrical problem with the torque converter clutch (TCC), which locks the engine and transmission together at cruising speed. Common causes include a faulty TCC solenoid, wiring shorted to power or ground, low or dirty transmission fluid, a worn clutch inside the torque converter, or, less often, a faulty computer. Cars with an automatic transmission use a torque converter, a fluid coupling between the engine and transmission. At highway speeds the computer applies a torque converter clutch (TCC) that locks the two together, which saves fuel and, as OBD-Codes.com notes, lowers transmission heat. The clutch is applied by an electric solenoid inside the transmission that directs fluid through the valve body. OBD-Codes.com says P0743 is set when the powertrain or engine control module (PCM/ECM) detects a fault in the TCC solenoid's electrical circuit. RepairPal describes it differently: its summary says the transmission control module (TCM) sets P0743 when the torque converter fails to lock the engine and transmission together, and its details say the PCM sees more than a 200 RPM difference between torque converter speed and transmission input shaft speed when the clutch should be locked. It is a generic OBD-II code for 1996 and newer vehicles, though repair steps vary by make and model. It is a sibling of P0740, P0741, P0742 and P0744.

Q: Can I keep driving with P0743?

Drive with caution, fix soon. Get it checked soon. RepairPal rates P0743 Urgent, meaning it can cause severe damage or be unsafe, and both sources say some cars may stall or nearly stall when coming to a stop after highway driving. OBD-Codes.com gives no severity rating and notes the fault may be intermittent. If the car stalls, shudders or won't shift into top gear, drive gently, avoid long stop-and-go trips and have it diagnosed promptly.

Reviewed 2026-10-23 · Based on 2 cited source(s)

What P0743 means

Cars with an automatic transmission use a torque converter, a fluid coupling between the engine and transmission. At highway speeds the computer applies a torque converter clutch (TCC) that locks the two together, which saves fuel and, as OBD-Codes.com notes, lowers transmission heat. The clutch is applied by an electric solenoid inside the transmission that directs fluid through the valve body. OBD-Codes.com says P0743 is set when the powertrain or engine control module (PCM/ECM) detects a fault in the TCC solenoid's electrical circuit. RepairPal describes it differently: its summary says the transmission control module (TCM) sets P0743 when the torque converter fails to lock the engine and transmission together, and its details say the PCM sees more than a 200 RPM difference between torque converter speed and transmission input shaft speed when the clutch should be locked. It is a generic OBD-II code for 1996 and newer vehicles, though repair steps vary by make and model. It is a sibling of P0740, P0741, P0742 and P0744.

Severity: can I keep driving?

Drive with caution, fix soon

Get it checked soon. RepairPal rates P0743 Urgent, meaning it can cause severe damage or be unsafe, and both sources say some cars may stall or nearly stall when coming to a stop after highway driving. OBD-Codes.com gives no severity rating and notes the fault may be intermittent. If the car stalls, shudders or won't shift into top gear, drive gently, avoid long stop-and-go trips and have it diagnosed promptly.

Common symptoms

Check engine light on (both sources)
Stalling or dying when coming to a stop after cruising on the highway (both sources; RepairPal says in some cases)
Shudder when taking off or coming to a stop (OBD-Codes.com)
Won't shift into the highest gear at freeway speed (RepairPal)
Lower fuel economy or misfire-like symptoms (RepairPal)
RepairPal says that in unusual cases the driver notices nothing

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Faulty torque converter clutch (lockup) solenoid (both sources)
Wiring or circuit shorted to power or ground (OBD-Codes.com)
Low or dirty transmission fluid; RepairPal says dirty fluid can restrict hydraulic passages (both sources)
Worn or failed clutch assembly inside the torque converter (both sources)
Faulty valve body or engine coolant temperature sensor (RepairPal)
Faulty PCM/ECM (OBD-Codes.com, which treats it as a last resort)
The sources differ: OBD-Codes.com treats P0743 as an electrical circuit fault, while RepairPal frames it as the converter failing to lock and lists hydraulic and mechanical causes too

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes and note the freeze frame data. OBD-Codes.com says to fix any engine sensor or lean/rich codes first, because many sensors feed transmission shift decisions.
Check the transmission fluid level and condition. OBD-Codes.com says a fluid and filter change (not a flush on a high-mileage transmission) often helps minor transmission issues.
Look over the external transmission harness, connectors and fuses, and make sure the transmission case is grounded to the body and battery.
The fault may be intermittent. OBD-Codes.com suggests clearing the code and watching whether it returns, and notes the internal harness can fail only when hot, cold, over bumps or in turns.
Check for technical service bulletins (TSBs) or an updated computer calibration from the dealer; OBD-Codes.com says a revised calibration may address this code.

Typical fixes

Repair wiring or connectors shorted to power or ground
Replace a faulty TCC solenoid, after checking it for debris (OBD-Codes.com found metallic debris on the solenoid caused it in the author's case)
Change transmission fluid and filter if the fluid is low or dirty
Repair the valve body or replace the torque converter if testing shows the clutch isn't locking
Reprogram or replace the PCM only after wiring and solenoid tests pass; a replacement must be programmed to the vehicle

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The car stalls, shudders or won't shift into top gear
Testing the solenoid means finding its wires on a wiring diagram, applying power and ground, and checking resistance against the factory service manual (OBD-Codes.com)
Inspecting the solenoid usually means removing the transmission pan
RepairPal says shops should duplicate the code on a test drive above 45 mph and compare converter RPM with input shaft RPM on a scan tool
The fluid smells burnt or is black, which OBD-Codes.com says can point to a worn converter clutch and a rebuilt or replacement transmission

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0743 serious?

RepairPal rates it Urgent, and both sources say some cars stall or nearly stall when coming to a stop after highway driving. OBD-Codes.com gives no severity rating. Get it diagnosed soon.

Can low transmission fluid cause P0743?

Yes. OBD-Codes.com lists low or dirty fluid as a cause, and RepairPal says dirty fluid can restrict the hydraulic passages. Checking the fluid level and condition is a cheap first step.

Does P0743 mean I need a new transmission?

Not necessarily. Both sources list the TCC solenoid and fluid problems, and OBD-Codes.com puts wiring checks first. A worn converter clutch can need a rebuilt or replacement transmission, but only test results should lead you there.

How much does it cost to fix P0743?

Neither source gives a repair cost. It ranges widely from a wiring repair or fluid service to a solenoid, valve body or torque converter, so get a diagnosis and written estimate first.

Sources

Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.