P0742 Code: Torque Converter Clutch Circuit Stuck On
The converter lockup clutch stays applied when it should be released, which can stall the engine at stops.
Stop driving
If the engine stalls or nearly stalls when you stop, don't drive in traffic: a stall means losing power steering and brake assist, and the car may not restart in gear. Shifting to Neutral before each stop is only a stopgap to reach a shop.
At a glance
Severity: High
- Meaning
- Torque Converter Clutch Circuit Stuck On
- System
- Transmission · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $100–$5,500
- DIY difficulty
- Hard
The torque converter clutch should only lock at cruising speed; when you slow down, the TCM releases it so the converter can slip and the engine keeps idling while the car is stopped in gear. P0742 sets when the TCM sees almost no converter slip at a time when lockup is commanded off. The effect is like stopping a manual-transmission car without pressing the clutch: the engine bogs, shakes or stalls as the car comes to a halt. The cause is usually hydraulic – a TCC solenoid or TCC valve stuck open by debris or varnish – but a wiring short that keeps the solenoid energized, or a converter clutch that drags internally, produces the same result.
How to read P0742
- P Powertrain
- 0 Generic (SAE)
- 7 Transmission
- 42 Specific fault
Symptoms
- Engine stalls or almost stalls when coming to a stop in Drive
- Rough, shaking idle in Drive that smooths out in Neutral or Park
- Car lurches or the engine bogs when shifting from Park into Drive or Reverse
- Engine feels like it's dragging, with weak acceleration from a stop
- Shudder when coasting down to low speed
- Check engine light, sometimes with P0741
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- TCC solenoid mechanically stuck open by debris or varnish
- TCC apply or regulator valve stuck in the valve body
- Wiring short keeping the solenoid energized
- Converter clutch dragging internally after overheating
- Debris-laden fluid from a failing converter or clutches
- TCM driver fault or software error commanding lockup
- Low engine idle speed making the drag worse
Diagnosis step by step
Confirm it's lockup, not an engine problem
Let the engine idle in Park, then in Drive with your foot firmly on the brake. A small rpm dip is normal; a heavy drop toward stalling that disappears in Neutral points to the converter clutch. On the scan tool, TCC slip near zero at a standstill with lockup commanded off confirms it.
Tools: OBD-II scanner
Unplug the solenoid to split the problem
With the engine off, unplug the transmission connector or TCC solenoid connector where accessible, then test the stall-at-stop again. If the problem disappears, the solenoid was being powered – look for a wiring short or a TCM fault. If it persists, the fault is hydraulic or inside the converter.
Tools: Screwdriver, OBD-II scanner
Check for a short in the control wire
Many TCC solenoids are switched on the ground side, so a control wire chafed against the body or transmission case keeps the solenoid on. Check the control wire for continuity to ground with the connector unplugged at both ends.
Tools: Multimeter, Flashlight
Inspect fluid and pan debris
Drop the pan and look at the filter and magnet. Fine friction material or metal suggests debris that jams valves; black, dusty material in large amounts can mean the converter clutch lining is breaking up.
Tools: Towels & shallow pan, Torque wrench
Service the valve body and solenoid
If electrical checks pass, a shop replaces the TCC solenoid and cleans or replaces the TCC valves in the valve body. Flush the cooler and lines so debris doesn't come straight back.
Replace the converter if it still drags
If stalling continues with the solenoid unplugged and the valve body serviced, the converter clutch is mechanically stuck and the torque converter has to be replaced.
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair shorted control wire | No | $100–$350 |
| Replace TCC solenoid, fluid and filter | No | $300–$800 |
| Clean or replace valve body | No | $600–$1,500 |
| Replace torque converter and flush cooler | No | $1,300–$2,800 |
| Transmission overhaul if debris has spread | No | $2,800–$5,500 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Ford | 2 | Expedition |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
P0742 lights the check engine light, and an OBD emissions test will fail with it on. Because the engine may stall at the test station, get it fixed first.
Frequently asked questions
Why does my car stall when I stop but not when I'm in Neutral?
In Neutral the engine is disconnected from the wheels. In Drive, a stuck lockup clutch ties the engine to the transmission like a manual car with the clutch pedal released, so stopping the wheels stops the engine.
Is P0742 electrical or mechanical?
It can be either, which is why unplugging the solenoid is such a useful test. If the stall goes away with the solenoid unplugged, look at wiring and the computer; if it stays, the valve body or converter is sticking.
Can I keep driving by shifting into Neutral at every stop?
It can get you to a shop, but it's easy to forget, and a stall in traffic removes power steering and brake assist. The underlying stuck clutch also heats and wears the converter.