DIYAUTOFIXESMANUALS

Diagnostic Trouble Code Database

P0740Moderate (Fix Soon)

Torque Converter Clutch (TCC) Circuit Malfunction

System:Transmission & Drivetrain•Classification:Powertrain (OBD-II Generic)•Severity Impact:Torque converter lockup clutch fails to engage on highway. Transmission runs hotter and highway fuel economy drops 10-15%.
Direct Technical Definition (Fast Answer)

Code P0740 indicates an electrical fault in the Torque Converter Clutch (TCC) solenoid circuit. The TCC solenoid locks the engine crankshaft to the transmission input shaft at highway speeds for 1:1 mechanical efficiency. When the circuit opens or shorts, lockup is disabled.

Estimated Repair Time60 – 120 minutes
DIY Parts Cost$35 – $110
Shop Repair Quote$350 – $850
Average DIY Savings$315 – $740
The 80/20 Workshop Rule

Inspect the external transmission wiring harness connector for transmission fluid wicking through pins. If dry, drop the transmission pan and measure TCC solenoid resistance (spec: 10–25 Ohms). Replace defective TCC solenoid ($40).

Estimated DIY Cost
$35 – $110
Tools & DIY parts
Dealership Shop Quote
$350 – $850
Labor ($180/hr) + parts
Net Money Saved
$315 – $740
In your driveway today

Interactive Symptom Pinpoint Troubleshooter

Answer 2 diagnostic tests to isolate the exact component failure for P0740.

DIAGNOSTIC TEST 1 OF 1Step 1

Is the TCC solenoid mounted on the exterior of the transmission case (Honda/Acura)?

Live Scanner & Multimeter Benchmark Values

Compare your live OBD-II PID sensor data against OEM factory operating specs for P0740.

Monitored Parameter / Sensor PIDHealthy OEM Operating RangeFault Threshold (Triggers P0740)
TCC Solenoid Coil Resistance
10.0 – 25.0 Ohms (depending on transmission)
OL (Open Loop) indicates severed internal wire coil
TCC Slip RPM (Highway Cruising 65 MPH)
0 – 20 RPM slip (locked 1:1)
>200 RPM slip confirms slipping lockup clutch friction

Symptoms Associated with P0740

Drivers typically observe the following symptoms when the ECM flags P0740:

Check Engine Light on
Engine RPM stays slightly higher at 65-75 MPH highway speeds
Loss of 2-4 MPG fuel economy on highway trips
Transmission fluid runs hotter than normal

Common Root Causes & Statistical Probability Matrix

Statistical breakdown of what triggers this code based on automotive repair shop data.

Defective or open-circuit TCC lockup solenoid
High ProbabilityDifficulty: Moderate
Relative Frequency: 75%Estimated Parts Cost: Low
Clogged solenoid hydraulic fluid screen
High ProbabilityDifficulty: Moderate
Relative Frequency: 75%Estimated Parts Cost: Low
Worn torque converter internal clutch friction lining
Low ProbabilityDifficulty: Hard
Relative Frequency: 20%Estimated Parts Cost: High

Step-by-Step Diagnostic & Repair Procedure

Follow this logical order to isolate and repair P0740 before spending money on costly parts.

Checklist Progress: 0 of 3 steps complete

Step 1: Check Fluid Level & Quality

Verify transmission fluid is pink/red, not dark black or burnt smelling.

Step 2: Test Solenoid Resistance

Probe TCC solenoid pins with multimeter (spec: 10-25Ω).

Step 3: Clean Solenoid Filter Screens

Inspect fine mesh screens for clutch material blockage.

Vehicle-Specific Failure Trends & Technical Bulletins

Real workshop failure patterns reported by mechanics across popular makes and models for P0740.

Honda Civic / Accord / Odyssey (4-Spd & 5-Spd Auto)

Common Failure Point:TCC lockup solenoid twin tubes mount externally on transmission case and clog with clutch debris.
Verified Workshop Fix:Remove external lockup solenoid assembly ($45), clean micro-screens with brake cleaner, and reinstall.

Dodge Ram / Grand Caravan (42RLE / 62TE)

Common Failure Point:Transmission solenoid pack internal contacts crack from thermal cycling.
Verified Workshop Fix:Replace solenoid block assembly mounted to valve body ($110).

Dave Miller, ASE Master Tech

ASE L1 Certified Master Reviewer

ASE Certified Master Automobile Technician (A1-A8) & L1 Advanced Engine Performance • 24 years automotive diagnostic experience

“Always verify sensor voltages and harness grounds before purchasing replacement electronic components.”

Editorial review and field diagnostic verification: Updated October 2026

Frequently Asked Questions About P0740

Yes, standard automatic gear shifting operates normally. However, avoid heavy towing because the torque converter will generate excess heat without lockup.