Input/Turbine Speed Sensor Range/Performance Problem
This code indicates a problem with the input or turbine speed sensor performance.
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 input speed sensor measures how fast the engine is spinning to help the transmission know when to shift gears. If it's not reading correctly, the transmission can't shift properly, which can lead to problems like slipping or hard shifting.
What the computer is actually seeing
The computer looks for a specific range of input speed signals from the sensor. If the voltage readings are outside of the expected range for a certain period, it sets this code.
What a healthy reading looks like
Expected voltage from the sensor is typically between 0.5V to 4.5V, depending on the vehicle and conditions. Speed readings should match engine RPM closely.
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.
- 1Check the vehicle's transmission fluid level and condition; top off or replace as needed. Decision Point: Is fluid level good? If no, refill and test. If yes, proceed.
- 2Inspect the wiring and connectors for the input speed sensor. Look for frays, corrosion, or loose connections. Decision Point: Are the connections secure? If no, repair them and test. If yes, proceed.
- 3Using a scan tool, monitor the input speed sensor's live data while the engine is running. Decision Point: Does the sensor provide readings within spec? If no, replace the sensor. If yes, proceed.
- 4Check for other related trouble codes in the system that could indicate a broader transmission issue. Decision Point: Are there other codes? If yes, diagnose those first. If no, consider TCM issues.
Common causes
- Faulty input/turbine speed sensor
- Wiring harness issues or damaged connectors
- Transmission fluid problems (low, dirty, or wrong type)
- Failed transmission control module (TCM)
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with code P0790?
It's not ideal; the transmission may shift erratically, which can lead to safety issues. Get it checked soon.
Will this code come back after clearing it?
If the underlying issue isn't resolved, yes, it will likely return.
Why does this pair with other codes?
Transmission issues often stem from multiple faulty components; several codes may indicate interrelated problems.
Working a real vehicle right now?
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