Transmission Speed Sensor A Failure
The Transmission Speed Sensor A is not transmitting a valid signal.
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)
This code means the computer isn't getting a clear reading from the speed sensor in the transmission, which helps it know how fast the vehicle is moving.
What the computer is actually seeing
The computer expects a variable voltage signal from the sensor that changes with vehicle speed, typically around 0.5V to 2.5V when the vehicle is moving. If it reads a constant voltage (like 0V or above 4.5V), it flags this code.
What a healthy reading looks like
Voltage signal from the transmission speed sensor should vary between 0.5V and 2.5V with vehicle speed.
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 transmission fluid level and condition. It should be clear and at the correct level; top off if low.
- 2Inspect the wiring and connectors for the speed sensor. Look for frayed wires, corrosion, or loose connections.
- 3Use a multimeter to measure the voltage at the speed sensor connector while the vehicle is moving. It should vary between 0.5V and 2.5V if functioning properly.
- 4If voltage is constant at zero or above 4.5V, replace the speed sensor. If voltage is within range, suspect a fault in the ECU or further wiring issues.
Common causes
- Faulty speed sensor
- Wiring or connector issues
- Transmission fluid level low or contaminated
- Electronic control unit (ECU) fault
Typical repair cost
$$ - $$$
Related codes
Frequently asked questions
Can I drive with this code active?
Yes, but you may experience erratic shifting or poor performance. Fix it soon.
Will this code come back after clearing?
It might if the underlying issue isn't fixed, so diagnostic steps are important.
Does this code indicate a bad transmission?
Not necessarily, it often points to the sensor or wiring, not the transmission itself.
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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