OBD-II trouble code
P0715: Input / Turbine Speed Sensor Circuit Malfunction
The transmission's input (turbine) speed sensor is reporting an erratic, missing, or impossible signal. This is the sensor that tells the transmission control module how fast the input shaft is spinning after the torque converter — the counterpart to the output speed sensor in P0720.
Quick facts
- System
- Powertrain
- Category
- Transmission / Speed Sensor
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $800
- DIY difficulty
- Intermediate DIY
Browse every code in P0700–P0799, or start from the full code library.
What does P0715 mean?
P0715 sets when the transmission control module loses or doesn't trust the signal from the input speed sensor — often called the turbine speed sensor. This sensor reads the speed of the transmission's input shaft, which is the shaft driven by the torque converter's turbine. If you've read about P0720, this is its sibling from the other end of the gearset: P0720 watches the output shaft (essentially road speed), while P0715 watches the input shaft (engine speed as it actually arrives at the transmission after passing through the converter).
The TCM needs both numbers to do its job. By comparing input speed to output speed it calculates the transmission's gear ratio in real time, which is how it confirms the transmission actually engaged the gear it commanded, detects slip, and manages torque converter clutch lockup. It also uses the input-vs-engine RPM difference to measure converter slip directly. When the input speed signal goes erratic or disappears, the TCM loses its ability to verify what's happening inside the transmission, and the unit holds the default gear its calibration selects, with adaptive shifting switched off, to protect the hardware.
The causes fall into three buckets. A failed sensor is one to test: the turbine sensor sits in hot fluid for its whole life. Wiring and connector faults are another, especially where the harness routes near the hot case or picks up road moisture. The third is internal — metal debris from transmission wear on the sensor tip, or damage to the reluctor the sensor reads. Because limp mode and the loss of the speedometer-adjacent functions arrive together, drivers usually notice this one immediately rather than letting it slide.
Common causes
- Failed input/turbine speed sensor
- Damaged or corroded sensor connector
- Broken or chafed wiring between the sensor and the TCM
- Metal debris from transmission wear on the sensor tip
- Damaged reluctor / tone ring inside the transmission (rare)
- Low or burnt fluid allowing clutch slip, which can produce an input-speed reading the TCM rejects as implausible
- TCM internal fault (rare — usually shows other codes too)
- Recent transmission repair where the sensor wasn't reseated properly
- Internal transmission damage producing an impossible input/output ratio
Symptoms
- Check engine light on with P0715 stored
- Transmission stuck in one gear (limp mode)
- Harsh, delayed, or erratic shifts before limp mode engages
- Erratic or flaring shifts as the TCM loses slip control
- Torque converter clutch not locking or cycling oddly
- Speedometer may be affected on platforms that derive speed partly from this signal
- Engine RPM doesn't correlate cleanly to gear changes
Diagnostic steps
- 1.Read live data on a brief test drive and compare input speed, output speed, and commanded gear. A failed input sensor reads zero or erratic input speed while output speed and road speed are clearly non-zero. This code commonly drops the transmission into limp mode without warning, so have a passenger read the tool or record the session for review — do not drive and watch a screen.
- 2.If you check the fluid, use the level procedure for this transmission. The input-speed sensor lives in that fluid, so a low or burnt level is worth knowing, but many units have no dipstick. Where the case has both a fill plug and a level plug, the level is read at the level plug. Removing the fill plug does not set the level. Acura bulletin 15-039 Version 4, September 17, 2018, which supersedes the September 9, 2017 issue, checks the level at the level plug with the engine running. Shutting the engine off with that plug out pours the ATF out. Fluid is added at the fill plug. The affected-vehicle table is 2016–2017 MDX, all 9-speed; 2018 MDX AWD and 2019 MDX 2WD only inside the VIN ranges printed in that table; 2015–2018 TLX, all 9-speed; and 2019 TLX only inside the VIN ranges printed in that table. The bulletin’s temperature window is not copied here as a number. The ATR 6L80 introduction handout, for some passenger-car 6L80 units with no dipstick, checks the level at the level-control plug in the pan with the engine idling in Park, and it uses the plugged dipstick hole as the fill point. Its temperature window is 86–122°F (30–50°C). The engine-running warning in the Acura bulletin belongs to the level plug, not the fill plug. Use the plugs and the temperature this transmission's procedure names.
- 3.Inspect the input/turbine sensor connector for corrosion, road damage, or a loose pin — a common and cheap fix.
- 4.Before reaching for a resistance test, count the wires at the sensor. A two-wire magnetic (variable-reluctance) pickup is a coil with a published resistance, so a reading well outside the manufacturer's figure condemns it. A three-wire Hall-effect or active sensor has no winding, so a resistance reading there means nothing at all — test that type by confirming its supply and ground and watching its output change with shaft speed.
- 5.Wiggle-test the harness from the sensor to the TCM while watching live data to catch an intermittent wiring fault.
- 6.If sensor and wiring check out, drop the pan to inspect for metal debris and reluctor damage — a substantially larger repair. Let the transmission cool first: fluid straight off a run is hot enough to scald, it will arrive faster than expected when the pan corner breaks loose, and the vehicle must be on stands or a lift rather than a jack, because this job puts your head and arms under it.
Repair cost
$150 – $800
Sensor replacement is the low end when the input sensor is bolted on the outside of the case. It climbs when the sensor sits behind the case and the pan has to come down. A connector or a chafed wire is a smaller branch of the same job. Fluid service, when the level procedure shows it is needed, sits in the middle of that sensor-and-fluid work. A damaged reluctor, or internal wear that requires the transmission to come apart, is outside this bracket. No price for that teardown is stated here. Rule the sensor in or out before you assume it. The two figures beside this note are a span for planning, not a quote. Add part prices to the labor time the service information lists for this unit.
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DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.