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The input speed sensor (also called the turbine speed sensor) reads how fast the input shaft / turbine is spinning, basically the speed coming out of the torque converter into the gearset. The TCM compares that to the output speed sensor to calculate gear ratio, control shift timing, and manage converter lockup. P0717 specifically means no signal from that sensor: the TCM was watching for pulses while the shaft was clearly turning, and saw zero.
That "no signal" wording matters. P0717 is different from P0716 (range/performance, a signal that is present but wrong) and P0715 (generic input sensor circuit). No signal points hard at an open circuit, a dead sensor, or a connector that lost contact. It is one of the more diagnosable transmission codes because the symptom is binary: the pulses are there or they are not.
What Triggers P0717
- Failed input speed sensor. The magnetic or hall-effect pickup dies and stops generating pulses. Most common cause by a wide margin.
- Open or shorted wiring. A broken wire, chafed harness, or a connector that backed out. Heat and vibration near the trans take their toll.
- Connector contamination. ATF or corrosion in the sensor connector pins breaking continuity.
- Damaged reluctor / tone ring. If the toothed ring the sensor reads is chipped or the gap is wrong, the signal drops out. Less common but real.
- Metal debris on the sensor tip. Magnetic sensors collect ferrous shavings; a heavy buildup masks the teeth. This one hints at internal wear elsewhere.
- TCM input fault. Rare, but the module's sensor input can fail.
What You Will Feel
With no input speed signal, the TCM loses a critical input and usually drops into limp mode to protect the transmission. Typical symptoms:
- Harsh, late, or erratic shifts, or no shifting at all (stuck in one gear).
- Limp mode, often locked in 2nd or 3rd, no overdrive.
- Speedometer or shift indicator acting up on some vehicles.
- Converter lockup not engaging.
How to Diagnose P0717
- Step 1 — Locate the sensor. The input/turbine sensor is usually on the transmission case, accessible from outside on many units. Find it before you order parts so you know what you are dealing with.
- Step 2 — Inspect the connector. Unplug it. Look for ATF, corrosion, bent or backed-out pins. Clean it and reseat it — sometimes that alone restores signal.
- Step 3 — Measure the sensor. Check resistance against spec for a magnetic type, or check reference voltage and signal for a hall-effect type. Out of spec or open means replace the sensor.
- Step 4 — Check the wiring. With the sensor unplugged, verify continuity from the sensor connector back to the TCM and check for shorts to ground or power.
- Step 5 — Watch live data. A scan tool showing input RPM should read zero with the fault, then jump to a real number once you fix it. That is your confirmation.
The Parts That Fix It
| Root Cause | Fix | Rough Part Cost |
|---|---|---|
| Failed sensor | Input/turbine speed sensor | $20–$80 |
| Connector contamination | Clean / replace connector | $0–$40 |
| Wiring open or short | Repair harness / pins | $15–$120 |
| Damaged tone ring | Internal repair (pan/teardown) | $100–$600+ |
The good news with P0717: in the large majority of cases it is the sensor or the connector, both cheap. Replacing an externally-mounted speed sensor is often a 15-minute job, unplug, unbolt, swap, plug back in. Order the correct sensor for your transmission, not a generic listing, because the connector and pickup type vary by unit.
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Shop Gearbox Insider →Can You Drive With P0717?
You can limp it home, but do not make a habit of it. In limp mode the transmission is stuck in a fixed gear with no overdrive and possibly harsh engagement; pulling out into traffic from a stop in 2nd or 3rd gear is sluggish and the higher engine RPM at speed builds heat. Fix the sensor, clear the code, and the transmission returns to normal shifting once it sees a valid input signal again.
Rough Total Cost
An externally accessible sensor at a shop runs roughly $120–$300 including diagnosis. Wiring repair adds labor. DIY, you are looking at the price of the sensor plus 20 minutes. The only expensive scenario is a damaged internal tone ring, which means going inside the transmission, but that is uncommon and usually comes with other symptoms.
FAQ
Is the turbine speed sensor the same as the input speed sensor?
Yes. Different manufacturers use different names for the same sensor that reads input-shaft / turbine speed coming out of the converter.
Why is my car stuck in one gear with P0717?
Losing the input speed signal forces the TCM into limp mode to protect the transmission, which holds a fixed gear. It returns to normal once a valid signal is restored.
Could P0717 be caused by something inside the transmission?
Occasionally, a chipped tone ring or heavy metal debris on the sensor. But check the sensor and wiring first; that is the cause the vast majority of the time.