P1744

Code

LINCOLN P — Powertrain

Torque Converter Clutch System Stuck in Off Position

Brand: LINCOLN

Type: P — Powertrain

Views: UK: 15 EN: 27 RU: 20

AI status

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Page language: EN

Causes

TCC solenoid failed (open/short or stuck)
Wiring problem: open, short to ground/power, high resistance, or corroded connector
Low, contaminated, or incorrect transmission fluid
Valve body or TCC control valve stuck or clogged
Insufficient transmission line pressure
Internal transmission wear (friction material, clutch pack) preventing lockup

Symptoms

No torque converter lockup at cruise (engine RPM higher than normal at highway speeds)
Reduced fuel economy during steady speed driving
Transmission slips or delayed acceleration under load
Possible shudder or harshness when attempting to engage (less common when stuck off)
MIL illuminated and stored DTCs related to TCC/torque converter

What to check

Read DTCs and freeze frame data; note related transmission codes
Road test with a scan tool, monitor TCC command vs TCC actual/apply status, transmission fluid temperature and line pressure (if available)
Check transmission fluid level, color and smell; correct fluid type
Inspect TCC solenoid connector and wiring for corrosion, pin damage, and secure fit
Measure TCC solenoid resistance and compare to factory spec
Backprobe and observe TCC command signal (voltage/PWM) from TCM while commanding apply with scan tool

Signal parameters

TCC command: PWM or ON/OFF signal from TCM; duty cycle range 0–100% (varies by model) — when commanded ON a measurable voltage/PWM should be present at the solenoid connector
TCC solenoid resistance: typical low-ohm coil value (example ranges commonly 8–30 ohms); consult factory spec for exact value
When TCC is successfully applied: transmission input speed and engine speed may change (RPM drop or torque transfer) — expected RPM change depends on vehicle
Line/apply pressure: increases when TCC is commanded (specific psi value varies by transmission — check factory hydraulic spec)
No command signal (0V/steady 12V) with TCM requesting lockup indicates wiring or module issue

Diagnostic algorithm

Confirm the code and check for other transmission or engine codes. Record freeze frame data.
Verify transmission fluid level, condition and correct fluid type. Top or replace fluid if low/contaminated and retest.
Road test with scan tool. Command TCC ON/OFF from the tool and observe TCC commanded vs actual status, engine RPM, and vehicle speed.
Visually inspect TCC solenoid connector and harness for corrosion, damage, pin push-out or bent pins. Repair any damage.
With connector disconnected, measure TCC solenoid coil resistance and compare to factory spec. If out of range, replace solenoid.
Backprobe the solenoid connector while commanding TCC ON. Verify presence of expected PWM/voltage signal and good ground reference. Repair wiring or connectors as needed.
If command is present but solenoid does not operate, bench-test or apply 12V (with safety precautions) to solenoid to check actuation. Replace if it does not operate correctly.
If solenoid and wiring test good, check transmission hydraulic function: measure line and apply pressure and inspect valve body for stuck valves or debris. Clean or repair valve body as required.
Check related switches/sensors (park/neutral switch, input/output speed sensors) and repair if they prevent lockup.
If electrical and hydraulic components pass, reflash or replace TCM/PCM only after confirming module is root cause and following OEM procedures.
After repairs, clear codes and perform a full road test and scan-tool verification of TCC commanded vs actual across operating conditions.

Likely causes

TCC solenoid electrical fault (connector corrosion or failed solenoid)
Low/dirty transmission fluid or incorrect fluid type
Sticking valve in valve body preventing apply pressure to the torque converter clutch
Open/short in TCC control circuit between module and transmission
TCM/PCM calibration or internal fault (less common)

Fault status

⚠️ Status

Torque Converter Clutch (TCC) system stuck in OFF position — TCM commanded lockup but TCC did not engage.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-4 hours

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P1744 — Torque Converter Clutch System Stuck in Off Position