Vehicle Speed Sensor Failure
The vehicle's speed sensor is not reporting correctly to the computer.
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 has a sensor that measures how fast it's going. If this sensor fails, the computer can't tell how fast you're moving, affecting speed-related systems.
What the computer is actually seeing
The computer expects a signal range of 0-5 volts depending on the speed (0V at 0 mph to 5V at max speed). If no signal or an incorrect voltage is detected, it triggers code C1200.
What a healthy reading looks like
0-5 volts from the speed sensor depending on 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 vehicle's wiring and connectors related to the speed sensor for signs of wear or damage.
- 2Verify that the vehicle speed sensor is receiving power; expected voltage supply is typically 5V.
- 3Test the output signal from the speed sensor with a multimeter while the vehicle is moving; it should vary linearly from 0 to 5 volts.
- 4Inspect the vehicle's ECM for any additional fault codes that may relate to this issue.
Common causes
- Bad vehicle speed sensor
- Wiring issue to speed sensor
- Faulty engine control module (ECM)
- Wheel speed sensor correlation issue
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code present?
It's safe to drive, but speedometer and cruise control won't work properly.
Will this issue come back once fixed?
If the root cause is addressed, the code shouldn't return.
What if this code pairs with another issue?
Other codes may indicate additional related problems, so investigate further based on those codes.
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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