Why does my Ford Five Hundred lose power and show the wrench light?

Short answer: On the Five Hundred with the CVT (a continuously variable transmission, which uses a steel belt between two pulleys instead of fixed gears), a wrench light with sudden loss of power usually means the transmission computer saw a pressure or speed problem and put the car in limp mode (a protective low-power mode). Restarting often clears it for a while, but the cause is usually inside the transmission. Check the fluid and codes first; owners were quoted several thousand dollars for a replacement.

Symptom: The engine revs but the car barely moves, as if it dropped into neutral; a wrench light and check engine light; a thump on a cold morning; it drives normally again after you shut it off and restart.

What to check first

1. Read the codes. Owners report P0701 (transmission control system performance), P0715 (input speed sensor circuit), P0730 (incorrect gear ratio) and U0001 (a communication-network code). Write them all down before anyone clears them.
2. Check the CVT fluid level and color with the right procedure for this transmission. Fresh Ford CVT fluid is light blue-green; brown fluid means it's overdue.
3. Ask about a drain-and-fill, not a flush, on a high-mileage car. A drain-and-fill swaps about half the fluid each time.
4. Check wiring and connectors at the transmission if the problem comes and goes, before agreeing to a replacement.
5. Get a second opinion from a transmission shop that knows this CVT before paying for a whole unit.

Likely causes

1. Low fluid pressure inside the CVT (worn pump, seal or O-ring, or a sensor). A member on r/MechanicAdvice explained that P0701 often sets because P0730 is there, and that the root issue is usually wrong fluid pressure at the pulleys.
2. Old or wrong transmission fluid. Owners with 200,000+ mile cars that were never serviced say repeated drain-and-fills with the correct Ford CVT fluid helped.
3. Wiring or connector fault. Worth ruling out when the car runs fine after a restart.

What it usually costs

One owner with a 2005 at about 97,000 miles was quoted about $4,485 plus labor by a dealer for a replacement transmission. A drain-and-fill with the correct fluid costs far less. Prices are from owner posts and vary by shop and region.

Is it safe to keep driving?

Not reliably. A sudden loss of power in traffic is dangerous, and limp mode can happen at highway speed. If the wrench light comes on, drive gently to a safe place and get it diagnosed before long trips. Verify with a mechanic.

DIY or shop?

DIY for reading codes and checking fluid. A careful owner can do a drain-and-fill with the correct Ford CVT fluid. Internal repairs or a replacement are shop jobs.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists no recall for the CVT transmission on the Ford Five Hundred for these model years (checked 2026-10-23). Other recalls may exist for your car, so check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• NHTSA complaints: 247 keyword-matched complaints for Ford Five Hundred 2005–2007 (of 1,073 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-23; keywords: CVT, transmission, limp, slip, loss of power, neutral, wrench). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In CVT Transmission WOES on FordForum.com, a 2005 owner at about 97,000 miles was told by the dealer the transmission needed replacing, quoted at about $4,485 plus labor.
• In this r/MechanicAdvice post, a 2005 AWD owner got limp mode, a check-transmission light and a loud thump on cold mornings, with P0701 and P0730. A reply explained that the codes point to wrong fluid pressure at the pulleys and listed bad pressure sensors, an unseated filter or an internal leak as causes.
• In this PY Online thread, a 2006 owner's car lost power at cruising speed as if it shifted into neutral, with the wrench and check engine lights and P0701, P0715 and U0001. Restarting cleared it each time. A member explained that the limp mode protects the transmission, so the problem is likely mechanical even if it comes and goes.
• In Cvt p0845 p0961 p0701 and Five Hundred Trans fluid change on FordForum.com, an owner who bought a never-serviced car at 210,000 miles did repeated 5-quart drain-and-fills (about half of the roughly 10 quarts) with Motorcraft CVT fluid, and the advice in the thread was a drain-and-fill rather than a full flush on cars over 150,000 miles.

Quick tip

If you're shopping for a Five Hundred, ask for proof of CVT fluid service and drive it from a cold start. If yours is already throwing the wrench light, get the codes read and the fluid checked before you sign off on a replacement.

Vehicle focus: 2005–2007 Ford Five Hundred with the CVT (the same transmission was used in the Mercury Montego and Freestyle). Cars with the 6-speed automatic are different.

Safety / mechanic note

A transmission that suddenly cuts power can leave you stranded in traffic. Verify with a mechanic.