What's the difference between P0740 and P0741?

They're two sides of the same torque converter clutch system. P0740 is a circuit code — the PCM has detected an electrical fault in the TCC solenoid circuit (open, short, or out-of-range resistance), so it can't reliably drive the solenoid. P0741 is a performance code — the circuit is electrically fine, but when the clutch is commanded to lock it still slips, which is a mechanical or hydraulic problem. P0740 points you at wiring and the solenoid coil; P0741 points you at fluid, the solenoid's hydraulic function, or the converter itself.

Can I keep driving with P0740?

In most cases yes. The transmission still shifts through its gears — you just lose torque converter lockup, so highway fuel economy drops a bit and cruise RPM runs higher than usual. The longer-term concern is extra heat in the transmission fluid from the converter never coupling, which shortens fluid life. It's not an emergency, but plan to address it within a few months, and sooner if other transmission codes appear.

Is P0740 usually the solenoid or the wiring?

Both are common, and because it's a circuit code you should rule out the cheap stuff first. Start with the connector — corrosion or a backed-out pin can cause the fault on its own. Then resistance-check the solenoid against spec; an open or shorted coil confirms a failed solenoid. Check harness continuity for an open or short before assuming the solenoid. A failed PCM driver is possible but uncommon, so it's the last thing to suspect.

How much does it cost to fix P0740?

If it's a wiring or connector repair, often $100-$300. A TCC solenoid replacement — the most common fix — runs $250-$700 depending on whether the pan or valve body must come off. A failed PCM driver is rarer and more expensive. Unlike P0741, a simple fluid service usually won't clear P0740 because the fault is electrical, so have the circuit and solenoid checked before paying for fluid work alone.

OBD-II trouble code

P0740: Torque Converter Clutch Circuit Malfunction / Open

The PCM has found an electrical problem in the torque converter clutch solenoid circuit — usually an open or shorted winding, a bad connector, or damaged wiring. Where P0741 means the clutch isn't locking (a performance fault), P0740 means the circuit that commands it has an electrical fault.

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 P0740 mean?

P0740 is the electrical-circuit member of the torque converter clutch family, and the cleanest way to understand it is against its sibling P0741. P0741 is a performance code: the clutch is commanded to lock and the RPM signature shows it's still slipping — a mechanical or hydraulic shortfall. P0740 is a circuit code: when the PCM electrically tests the TCC solenoid circuit, it finds a problem in the wiring itself — an open winding, a short, an out-of-range resistance, or a missing return signal. In other words, P0741 says 'the clutch didn't do its job'; P0740 says 'I can't drive the clutch's solenoid properly in the first place.'

The torque converter clutch is a small lockup clutch inside the converter that mechanically couples the engine to the transmission once you're cruising, eliminating the slip a converter normally has. That lockup is what lets the engine settle into low RPM on the highway and deliver the fuel economy on the window sticker. The PCM controls it by switching current through the TCC solenoid in the valve body. P0740 sets when the electrical path to that solenoid fails the PCM's self-check: the solenoid coil has gone open or shorted, the connector has corroded, a wire has chafed or broken, or the PCM's driver circuit has failed.

Because it's an electrical fault, the common causes lean toward the wiring and the solenoid coil rather than fluid condition. A failed TCC solenoid (electrically open or shorted) is the most frequent cause, followed by connector and harness problems where the circuit runs into the hot transmission case. Worn solenoids, internal valve-body wiring, and PCM driver faults round it out. Drivers typically notice the same things as P0741 — no lockup, so slightly worse highway fuel economy, cruise RPM that sits a couple hundred higher than it used to, and sometimes no overdrive feel — because the end result is the same lost lockup, just reached through an electrical fault instead of a mechanical one. The transmission usually still shifts cleanly through the gears.

Common causes

Electrically open or shorted TCC solenoid coil (most common)
Corroded or damaged TCC solenoid connector
Broken, chafed, or shorted wiring to the solenoid
Internal valve-body wiring or harness fault
Failed PCM driver circuit for the TCC solenoid (less common)
Worn TCC solenoid that's begun to fail electrically
Moisture or fluid intrusion into the solenoid connector
Recent transmission service where the internal harness wasn't reconnected properly
Aftermarket tune altering or disabling TCC operation

Symptoms

Check engine light on with P0740 stored
Torque converter clutch never locks up
Highway fuel economy down a couple of MPG
Engine RPM sits higher than usual at steady cruise speeds
No noticeable shift into 'overdrive lockup' on the highway
Possible harsher feel as the converter never couples
Transmission otherwise shifts through all gears normally

Diagnostic steps

1.Scan and note whether P0740 is present alone or with P0741/P0742/P0743. P0740 specifically flags an electrical-circuit fault, which steers you toward wiring and the solenoid coil.
2.Inspect the TCC solenoid connector for corrosion, fluid intrusion, or backed-out pins — a frequent and cheap cause.
3.Resistance-check the TCC solenoid against the manufacturer's spec; most read roughly 10-20 ohms. An open or shorted reading confirms a failed solenoid.
4.Check continuity of the wiring from the PCM to the solenoid to find an open or short in the harness.
5.Verify the PCM is actually commanding and driving the circuit in live data before condemning the solenoid.
6.Confirm transmission fluid level and condition while you're in there — clean fluid is needed after any valve-body work anyway.

Repair cost

$150 – $900

Because P0740 is an electrical fault, the fix is often a TCC solenoid replacement at $250-$700 depending on whether the pan or valve body has to come off. A wiring or connector repair can be cheaper, $100-$300, when the fault is in the harness rather than the solenoid. A failed PCM driver is uncommon but pushes the cost up. Unlike P0741, a fluid service alone rarely clears P0740 since the problem is electrical, not hydraulic — though fresh fluid is still part of any valve-body job.

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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.

Related codes

P0741 P0742 P0743 P0744 P0700 P0750