P0740 on Mercury: How to Diagnose & Fix
Torque Converter Clutch Circuit Malfunction
1 Mercury model · 1 documented issue · 1 critical
P0740 on Mercury by model: symptoms, diagnosis and fix
Manufacturer bulletins on file with NHTSA describe several different CD4E transmission faults on 1999-2002 Cougars: no forward engagement (NHTSA items 605229 and 6091763), the ring gear side-loading the forward-clutch snap-ring retainer on 1999 models (item 607645), intermittent loss of first and second gears with code P0758 or P0740 (item 619324), and harsh or delayed shifts after speed-sensor service (item 630631). These faults share the CD4E transmission but do not point to one single valve-body or drum cause.
Common Symptoms
- No forward engagement in Drive (reverse may still work)
How to Fix
Preserve all transmission codes and freeze-frame data, identify which gears are lost, test line pressure and solenoid circuits, verify fluid level and condition, and inspect the transmission tag and prior repairs. Follow the symptom- and build-specific Ford procedure before choosing a sensor, solenoid, valve-body repair, hard parts or a remanufactured unit. Do not buy a transmission or rebuild kit until the failed part has been identified.
Sources for this issue (2)
P0740 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0740 mean on a Mercury?
P0740 stands for "Torque Converter Clutch Circuit Malfunction." This code indicates an electrical malfunction in the torque converter clutch (TCC) solenoid circuit of an automatic transmission. The torque converter clutch mechanically locks the engine to the transmission at cruising speed to improve fuel economy and reduce slippage, and it is engaged by a solenoid controlled by the transmission computer. The code sets when the computer detects an open, short, or out-of-range condition in the TCC solenoid circuit. A clutch that is commanded on but slips or won't hold sets a separate code (P0741). Common signs include the converter not locking up (higher cruise RPM and poor fuel economy), a check engine light, or stalling when coming to a stop if the clutch stays applied. On Mercury it is documented across 1 model: Cougar.
What are the most common causes of P0740?
The most common causes of P0740 are: Faulty torque converter clutch (TCC) solenoid, Wiring or connector fault in the TCC circuit (open or short), Transmission case connector or internal harness damage, including fluid intrusion, Internal transmission electrical short, Faulty transmission control module. The specific cause varies by vehicle.
How much does it cost to fix P0740 on a Mercury?
Repair costs vary widely with the root cause and Mercury model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.