Vehicle Speed Sensor A Circuit
This code indicates an issue with the vehicle speed sensor circuit.
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 vehicle’s computer is getting wrong speed info from the sensor that tells it how fast the truck is going, so it can't calculate things like transmission shifts properly.
What the computer is actually seeing
The ECM expects a varying voltage signal from the speed sensor as the vehicle speeds up and slows down, usually between 0.5V and 5V depending on speed.
What a healthy reading looks like
Signal voltage should be between 0.5V (0 mph) to 5V (speed exceeds 70 mph).
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 connectors to the vehicle speed sensor for damage or corrosion. Repair any issues found. Decision: If wiring and connectors are good, go to step 2.
- 22. Measure the voltage at the speed sensor connector while the vehicle is moving. Check if the readings are within the expected voltage range (0.5V to 5V). Decision: If readings are correct, suspect an ECM issue; if incorrect, proceed to step 3.
- 33. Replace the vehicle speed sensor. Decision: After replacement, clear the codes and test drive the vehicle to see if the code returns.
Common causes
- Faulty vehicle speed sensor
- Wiring issues or damaged connectors
- ECM malfunction
- Faulty transmission output shaft sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It may be drivable, but expect shifting issues and possible speedometer inaccuracies.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code will likely return after driving.
Why does this code pair with other speed sensor codes?
These codes often trigger together due to shared wiring or related sensor functions.
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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