The Lemon IndexThe transmission's output speed signal is erratic. Full P0721 page
19 owner complaints · the #8 code Ford F-Series owners name · 3% of Ford F-Series complaints that name a code (every car: 0.1%)
Middle of 169,000 miles · most between 130,000 and 175,000 (5 owners gave it)
Ford F-Series owners named P0721 in 19 complaints to the U.S. government (NHTSA), most often on the 2013, 2015 and 2014 model years, at a middle of 169,000 miles. The part they name most is the engine software (a reflash) (5 complaints). Complaints are owner reports, not proof of a defect.
Ford F-Series model years that report P0721
Owner complaints naming P0721, by model year. Raw counts: years that sold more get more complaints, so this is each model year's record, not a failure rate.
Mileage when it happened
169,000 miles is the middle of what 5 owners entered. Half were between 130,000 and 175,000 miles.
The mileage on the complaint form, when the owner gave one.
What owners say caused it or fixed it
The most-named part is the engine software (a reflash), in 5 of the 19 complaints (26%). 5 of those mention it being replaced or repaired, and 1 say the problem came back afterwards. Next: valve body or shift solenoid (5), engine computer (ECM / PCM) (4) and wheel speed (ABS) sensor (2).
- Software update (reflash)5 complaints5 mention a repair or replacement, 1 of them says the problem came back
- Valve body or shift solenoid5 complaints5 mention a repair or replacement, 1 of them says the problem came back · what Ford F-Series owners paid
- Engine computer (ECM / PCM)4 complaints4 mention a repair or replacement, 1 of them says the problem came back · what Ford F-Series owners paid
- Wheel speed (ABS) sensor2 complaints2 mention a repair or replacement
10 complaints mention a recall.
Counted from the owners' own words: a part counts when a sentence names it with a cause or repair word. What owners wrote, not a diagnosis. A shop should confirm the cause before replacing parts.
Symptoms owners describe with P0721
42% of these complaints say the check engine light came on.
- Loses power or goes into limp mode26%5 of 19 complaints
- Warning lights and electrical faults21%4 of 19 complaints
- Transmission slips or shifts hard16%3 of 19 complaints
Share of the complaints naming P0721 whose text also describes each problem. A complaint can describe more than one.
Codes owners report with it
Other codes named in the same Ford F-Series complaints, and in how many.
Repair costs
Ford F-Series valve body replacement cost · Ford F-Series ECM (engine computer) replacement cost
Recalls on these Ford F-Series years
- Transmission & drivetrain · 2014 · issued 2026
A loss of signal between the transmission output shaft speed sensor and the powertrain control module (PCM) can cause the transmission to unexpectedly downshift into first gear. NHTSA 26V378000 - Transmission & drivetrain · 2015 · issued 2026
A loss of signal between the transmission range sensor and the powertrain control module can cause the transmission to unexpectedly downshift into second gear. NHTSA 26V237000 - Transmission & drivetrain · 2014 · issued 2024
A loss of signal between the transmission output shaft speed sensor and the powertrain control module can cause the transmission to unexpectedly downshift into first gear, regardless of vehicle speed. NHTSA 24V444000 - Transmission & drivetrain · 2013 · issued 2019
The software used to reprogram the PCM did not have the necessary updates to prevent the transmission from unexpectedly downshifting into first gear, regardless of vehicle speed. NHTSA 19V433000 - Transmission & drivetrain · 2012, 2013 · issued 2019
The transmission may unexpectedly downshift into first gear, regardless of vehicle speed. NHTSA 19V075000
7 recalls for the same systems (powertrain) on the Ford F-Series model years above. A recall for the same system isn't proof it's behind P0721. Recall work is free at any dealer: check a VIN at nhtsa.gov/recalls or with our VIN check.
Keep going
- P0721: meaning, causes and every car that reports it
- Ford F-Series reliability by year
- 2013 Ford F-Series problems and recalls
Other codes Ford F-Series owners report
P0720 P0722 P2112 P0707 P0706 P1702 P0016 P0705 P07F7 P0430
The details
How we count
We read every owner complaint in the NHTSA file whose text names this trouble code, and count the ones filed about this model (matched by the make, model and model year on the complaint). Mileage is what the owner entered on the form.
Parts: a complaint counts for a part when one of the owner's own sentences names that part together with a cause word (failed, bad, diagnosed, caused by, leaking ...) or a repair word (replaced, repaired, new, reprogrammed ...). "Came back" means the same complaint also says the problem returned or the repair didn't fix it. These are counts of what owners wrote, not a diagnosis, and one complaint can name several parts.
Complaints are reports, not proof of a defect, and most owners never file one. Popular models get more complaints, so the counts are not a failure rate. The code meaning is the standard SAE J2012 definition in our own words, or the carmaker's meaning where we verified it for that make.
What P0721 means
The transmission's output speed signal is erratic.
Fix soon. Book a shop visit this week. Stop driving if the car slips, shakes, overheats or warns you.
- Failing output speed sensor
- Wiring fault
Check the complaints yourself
NHTSA complaint numbers (search them at nhtsa.gov): 11773964, 11767921, 11763752, 11732468, 11725153, 11704709, 11685282, 11666819, 11646110, 11640475, 11633938, 11628696 and 7 more.
Quick answers
What does P0721 mean on a Ford F-Series?
Output Speed Sensor Circuit Range/Performance. The transmission's output speed signal is erratic.
Which Ford F-Series years have the most P0721 complaints?
In complaints to NHTSA, owners of the 2013 (8), 2015 (5), 2014 (4) Ford F-Series named P0721 most (19 complaints in all, 2012–2015). Raw counts, not a failure rate.
What fixes P0721 on a Ford F-Series?
Owners most often name the engine software (a reflash) (5 of 19 complaints), then valve body or shift solenoid and engine computer (ECM / PCM). That's what owners wrote, not a diagnosis: have a shop confirm the cause with a scan and tests before replacing parts.
At what mileage does P0721 show up on a Ford F-Series?
Owners who gave their mileage reported a middle of 169,000 miles; half were between 130,000 and 175,000 (5 owners).
Can I drive my Ford F-Series with P0721?
Fix soon. Book a shop visit this week. Stop driving if the car slips, shakes, overheats or warns you.
Sources: NHTSA owner complaints that name P0721 on the Ford F-Series, counted by The Lemon Index; NHTSA recalls; repair bills owners named. Meanings: SAE J2012 in our own words. Owner reports, not a diagnosis or repair advice for your car.