Shop All Transmission Parts →
P0722 is one of the easier transmission codes to fix and one of the easiest to waste money on. The output speed sensor (OSS) reads a toothed reluctor on the output shaft or park gear and tells the PCM how fast the driveshaft is turning. That number feeds shift timing, torque converter clutch apply, line pressure, and on many vehicles the speedometer and cruise control.
P0722 specifically means no signal. The PCM sees engine RPM, maybe wheel speed from the ABS module, and a transmission in gear, but the OSS reports zero. That is different from its cousins:
- P0720: general output speed circuit fault. Broad, often set alongside P0722.
- P0721: signal present but erratic or out of range. Think loose sensor, chipped reluctor tooth, or electrical noise. See our P0721 guide.
- P0722: flatline. Open circuit, dead sensor, sensor tip too far from the reluctor, or a reluctor that is not spinning.
This applies to GM 4L60E, 4L80E and 6L80, Ford 4R70W, 5R55 and 6R80, Chrysler 45RFE, 545RFE and 68RFE, Toyota and more. Connector location and specs vary, so keep service data handy. 4L60E owners, see our P0722 4L60E fix.
Symptoms
| Symptom | Why It Happens |
|---|---|
| Speedometer dead or jumping | On many trucks and RWD cars the OSS is the vehicle speed source. No signal, no needle. See speedometer not working. |
| Harsh, late, or random shifts | The PCM schedules shifts off output speed. With no input it guesses or falls back to a default table. |
| Limp mode, stuck in one gear | Many PCMs command a failsafe gear (often 2nd, 3rd or 4th depending on the unit) with high line pressure. |
| Cruise control will not set | Cruise needs a valid vehicle speed signal. |
| ABS or traction light on | On some vehicles the VSS signal is shared with the ABS module, so a dead OSS lights it up too. |
| No TCC lockup, poor highway mileage | Converter clutch apply is locked out without a valid speed reading. |
Causes, Most Likely First
1. Connector corrosion or fluid wicking
This is the one we see most. The OSS connector lives low on the case or tailhousing where it eats road salt and water. Pull it and look for green crust, pushed-back pins, or a broken lock tab. Also look for ATF inside the connector. A leaking sensor O-ring can let fluid wick up the harness, and oil-soaked terminals lose contact.
2. Harness chafe or heat damage
The OSS lead often runs near the exhaust, over the crossmember, or along the transfer case. Look for melted loom and wire rubbed through to copper. A wire shorted to ground or burned open gives you a flatline. Flex the harness with the engine running and a scan tool on vehicle speed; if the reading pops in and out, you found it.
3. Metal debris on the magnetic tip
Magnetic sensors collect fine clutch and gear dust. A thick fuzz on the tip weakens the signal until the PCM stops seeing it, especially at low speed. Clean it and look at the pan. A little paste is normal wear; chunks mean internal damage and the code is a symptom, not the problem.
4. Failed sensor
Coils open up with heat cycles. Common and cheap, but it belongs fourth on this list, not first.
5. Damaged or missing reluctor
If the tone ring on the output shaft or park gear is cracked, spun, or missing teeth, the sensor has nothing to read. Also check anything that changes where the reluctor sits: a new tailhousing, a 2WD/4WD swap, or a rebuilt unit with the wrong parts. The sensor is fine and the code stays.
6. PCM or TCM
Rare. Only blame the module after you have proven a good signal arriving at its connector with the key on.
Testing: Prove It Before You Buy
Know what kind of sensor you have
Most older and many current units use a 2-wire magnetic (variable reluctance) sensor. It generates its own AC signal. Many newer designs use a 3-wire hall-effect sensor that needs a reference voltage and ground and outputs a square wave. The tests are different, and using the wrong one gives you a wrong answer.
2-wire magnetic: resistance
Unplug the sensor and measure across its two pins. Many 2-wire magnetic sensors fall somewhere around 1,000 to 2,500 ohms at room temperature, but the spec varies by manufacturer and model, so check your service data. Open (OL) means the coil is broken. Near zero means it is shorted. Also check each pin to the case; any continuity to ground is a fail. Then check the harness from sensor connector to PCM connector for continuity and shorts.
2-wire magnetic: AC voltage
Resistance can pass on a sensor that still does not produce output. With the drive wheels safely off the ground and the vehicle secured, set your meter to AC volts across the sensor pins and spin a wheel by hand or idle it in gear. You should see voltage that climbs with speed. Hand spinning often gives only a few hundred millivolts; if you see nothing at all, the sensor, the air gap, or the reluctor is the problem.
Scope it if you can
A magnetic sensor should show a clean sine wave growing in amplitude and frequency with speed; a missing peak every revolution means a damaged reluctor tooth. A hall sensor should show a crisp square wave.
3-wire hall-effect
Key on, back-probe the connector. Check the reference (commonly 5 or 12 volts, depending on design) and the ground. No reference means a wiring or module problem, and replacing the sensor is money thrown away. If power and ground are good, check the signal wire toggling as the output shaft turns.
Still stuck on whether the fault is the sensor or something hydraulic? Our speed sensor diagnosis guide and sensor vs solenoid breakdown go deeper.
Replacement Notes
- New O-ring every time. Lube it with ATF. A dry or reused O-ring leaks and starts the wicking problem again.
- Clean the bore. Wipe out debris before installing. Grit in the bore can hold the sensor off its seat and open the air gap.
- Do not overtighten the bolt. Hold-down bolts are low torque and plastic ears crack. The sensor should seat flush by hand; never pull it down with the bolt.
- Clean the connector. Fix any corrosion or damaged terminals now, or the new sensor inherits the old problem.
- Top off fluid, clear codes, road test. Watch output speed on the scan tool. It should track vehicle speed smoothly from a stop.
What It Costs
| Item | Typical Range | Notes |
|---|---|---|
| Output speed sensor (part) | $25 to $120 | OE and name-brand sensors sit at the upper end |
| DIY replacement | Part plus an O-ring and a little ATF | Usually a one-bolt job, 20 to 60 minutes |
| Shop labor | About 0.5 to 1.5 hours | More where a heat shield, crossmember or transfer case is in the way |
| Connector or harness repair | $0 to $150 | Pigtail and solder, or a shop hour |
| Reluctor or internal damage | Varies widely | Tailhousing or unit teardown; get it diagnosed first |
For GM units, the GM Genuine 24203876 input/output speed sensor is the OE piece. If you are doing both sensors on a 4L60E, the 4L60E input and output speed sensor set is cheaper than buying twice, and if the input side also threw P0715, replace them together. Doing a pan-down service on a 4L80E anyway? The 4L80E master solenoid kit with harness, filter and speed sensors covers it in one box.
Need Parts? Ships Same-Day
Input and output speed sensors, sensor sets, and solenoid kits for GM, Ford, Chrysler and import transmissions. Same-day ship before 2pm Eastern. Rebuilders can also browse the sensors collection at Core Transmission Parts.
Shop Speed Sensors →FAQ
Can I drive with a P0722 code?
Short distances, carefully. Many vehicles go into limp mode or shift erratically with no output speed signal, the speedometer may read zero, and cruise control is disabled. Fix it soon, because harsh or wrong-gear shifts put extra wear on clutches and bands.
What is the difference between P0720, P0721, and P0722?
P0720 is a general output speed sensor circuit fault. P0721 means the signal is present but out of range or erratic. P0722 means the PCM sees no signal at all while other inputs say the vehicle is moving. No signal points first at an open circuit, a dead sensor, or a missing reluctor.
Will a new sensor always fix P0722?
No. Connector corrosion, a chafed harness, and metal debris on the sensor tip cause a large share of P0722 codes. Test the circuit and inspect the old sensor before buying one, or the code can come right back with a new part installed.
Do I need to drain the transmission fluid to replace the output speed sensor?
Usually not. On most rear-wheel-drive units the sensor sits in the tailhousing or case above the fluid level, so you lose only a small amount. Top off and check the level afterward. Some front-wheel-drive and 4WD layouts differ, so check your service data.