OBD-II trouble code
P0743: Torque Converter Clutch Circuit Electrical
An electrical fault has been confirmed in the torque converter clutch solenoid circuit — typically an open or shorted solenoid winding, a damaged connector, or a wiring fault. It's the explicitly electrical sibling of P0740, and on many vehicles the two are nearly interchangeable.
Quick facts
- System
- Powertrain
- Category
- Transmission / Torque Converter
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $900
- DIY difficulty
- Shop recommended
What does P0743 mean?
P0743 specifically flags an electrical fault in the torque converter clutch solenoid circuit. It belongs to the same group as P0740, and a useful thing to know up front is that manufacturers don't all use these numbers identically. Some makes set P0740 as the general TCC circuit malfunction and reserve P0743 for a confirmed electrical fault (open or short); other makes lean on P0743 as their primary electrical-fault code and use P0740 more loosely. The practical takeaway is the same regardless of which number your scan tool shows: P0743 means the PCM has tested the solenoid circuit electrically and found it out of spec — it cannot reliably energize the TCC solenoid.
Electrically, the circuit is simple: the PCM switches current through the TCC solenoid coil to apply the lockup clutch. P0743 sets when that path fails the PCM's self-check — the coil has gone open or shorted, a wire is broken or chafed to ground or power, a connector has corroded, or the PCM's own driver circuit has failed. Because the diagnosis is electrical rather than hydraulic, the high-yield checks are resistance-testing the solenoid coil against spec and verifying continuity of the wiring, not chasing fluid condition. That's the key contrast with the performance code P0741: P0741 is about whether the clutch physically did its job; P0743 is about whether the circuit can command it at all.
The driver-facing result is the familiar lost-lockup picture — no torque converter lockup, so highway fuel economy slips a couple of MPG, cruise RPM sits higher than it used to, and the engine never settles into its low-RPM 'overdrive' note. The transmission generally still shifts through all its gears, because the fault is confined to the lockup circuit. Since P0743 is electrical, a transmission fluid service alone rarely clears it — the fix is almost always at the solenoid, the connector, or the wiring.
Common causes
- Open or shorted TCC solenoid coil (most common)
- Corroded, loose, or damaged TCC solenoid connector
- Wiring shorted to ground or to power
- Broken or chafed wire in the TCC circuit
- Internal valve-body harness fault
- Failed PCM driver circuit for the TCC solenoid (less common)
- Moisture or fluid intrusion into the solenoid connector
- Internal transmission harness damaged during a prior repair
Symptoms
- Check engine light on with P0743 stored
- Torque converter clutch never locks up
- Highway fuel economy down a couple of MPG
- Engine RPM higher than usual at steady cruise
- No noticeable lockup 'overdrive' feel on the highway
- Transmission otherwise shifts through all gears normally
- May set alongside P0740 on some platforms
Diagnostic steps
- 1.Note whether P0743 is present alone or with P0740/P0741 — P0743's electrical designation steers you straight to the solenoid coil and wiring.
- 2.Inspect the TCC solenoid connector for corrosion, fluid intrusion, or backed-out pins.
- 3.Resistance-check the TCC solenoid against the manufacturer's spec (most read roughly 10-20 ohms). Open or shorted confirms a failed solenoid.
- 4.Check continuity of the wiring from the PCM to the solenoid to locate an open, and check for shorts to ground or power.
- 5.Confirm in live data that the PCM is commanding the circuit but not seeing the expected feedback.
- 6.Suspect the PCM driver only after the solenoid and wiring test good — it's the least common cause.
Repair cost
$150 – $900
Like P0740, this is an electrical fault, so the common fixes are a TCC solenoid replacement at $250-$700 (depending on pan/valve-body access) or a wiring/connector repair at $100-$300 when the fault is in the harness. A failed PCM driver is uncommon but pushes the cost up. A fluid service alone rarely clears P0743 since the problem is electrical, though fresh fluid is part of any valve-body job. Resistance-test the solenoid before deciding.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission shift solenoid replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.