Transmission Input Shaft Speed Sensor - Out of Range
The input shaft speed sensor is reading values that are too high or too low.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer checks how fast the input shaft is spinning but sees a number it's not supposed to—either too fast or too slow. Sounds like a bad sensor or signal issue to me.
What the computer is actually seeing
The transmission control module expects to see input shaft speed readings typically between 0 to 4000 RPM. If the readings are outside this range, it triggers the fault code SPN 2781.
What a healthy reading looks like
Input shaft speed should be nominally between 200 RPM and 2500 RPM during normal operation, may not exceed 4000 RPM under load.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the wiring and connector for damage. Repair any issues found. Decision: Was there a wiring issue? If yes, fix it and retest. If no, move to step 2.
- 22. Inspect the input shaft speed sensor. Look for signs of wear or failure. Decision: Is the sensor damaged? If yes, replace the sensor and retest. If no, move to step 3.
- 33. Check transmission fluid level and quality. Correct if low or contaminated. Decision: Is the fluid good? If no, change it and retest. If yes, move to step 4.
- 44. Check for any pending or repeat fault codes. Decision: Are there other codes? If yes, address those first. If no, you may need to evaluate the transmission control module.
Common causes
- Faulty input shaft speed sensor
- Wiring issue (frayed or shorted wires)
- Bad connector at the sensor
- Transmission fluid level low or contaminated
- Faulty transmission control module
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; drivability may be affected. Drive cautiously and repair soon.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code will likely reappear.
Why does this code come up with other transmission codes?
They can indicate a related issue with the sensor, wiring, or transmission control system.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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