When your 2018 Ford Taurus sets a P0700 code, the transmission control module (TCM) has detected a fault in the transmission system. While P0700 itself is a general alert, accompanying codes in the TCM reveal specific issues that may point to actual TCM failure or other transmission problems.
Understanding P0700
P0700 is an information code that appears in the engine control module when the transmission control module has set diagnostic trouble codes. It's essentially a flag telling technicians to scan the TCM for the actual fault codes. By itself, P0700 doesn't identify the specific problem—you must retrieve codes from the TCM directly.
2018 Taurus Transmission
The 2018 Taurus uses Ford's 6F55 six-speed automatic transmission, controlled by a sophisticated TCM that manages shift timing, pressure, and torque converter lockup. The TCM also communicates with the engine computer to coordinate power delivery during shifts. Modern transmissions are highly dependent on electronic control.
Symptoms of TCM Failure
Erratic shifting—shifts at wrong times or wrong RPM. Transmission stuck in one gear (limp mode). No engagement into drive or reverse. Multiple transmission codes stored simultaneously. Harsh shifts or delayed engagement. Transmission operating normally in some conditions but failing in others.
TCM Versus Internal Transmission Problems
P0700 can indicate either TCM failure or internal transmission problems that the TCM is correctly detecting. Accompanying codes help differentiate: codes indicating electrical/communication issues often point to TCM failure, while codes for pressure, clutch, or solenoid issues suggest internal transmission problems. A failing TCM may set random, inconsistent codes that change between scans.
Diagnostic Approach
Scan the TCM directly for specific codes. Check for TSBs related to your specific code combination. Verify TCM power and ground connections. Check for water intrusion at the TCM location. If multiple seemingly unrelated codes appear, TCM failure is more likely. If codes consistently point to one circuit or component, internal transmission issues are more probable.
Repair Costs
TCM replacement typically costs $400-$800 for the module plus $100-$200 for dealer programming. If internal transmission problems exist, repair costs vary widely from $500 for solenoid replacement to $3,500+ for rebuild. Accurate diagnosis before parts replacement prevents unnecessary expense.