P0503 means Vehicle Speed Sensor A Intermittent/Erratic/High. The vehicle speed signal is dropping out, jumping or reading higher than possible. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0503 means
Most engine sensors receive a 5-volt reference and return a signal between roughly 0 and 5 volts. Codes ending in circuit high or circuit low usually point to an electrical fault: an open circuit, a short or an unplugged connector. Range/performance codes mean a signal is present but disagrees with what the computer expects from the other sensors, which more often points to a dirty sensor, an air leak or a mechanical problem.
P0503 symptoms
- Speedometer needle jumping
- Erratic shifts
- Check engine light
Common causes of P0503
- Loose or corroded connector
- Wiring rubbing or damaged
- Failing sensor
- Electrical interference from aftermarket wiring
How to diagnose P0503
- Wiggle-test the wiring while watching speed on a scan tool
- Inspect the connector for corrosion
- Check grounds
Can you drive with P0503?
Yes, carefully.
P0503 tips
Aftermarket electronics spliced into the speed sensor wiring, such as some trailer or remote-start installations, can cause erratic speed signals. On vehicles that take vehicle speed from the ABS wheel speed sensors, a damaged tone ring or a wheel bearing with play can also make the signal jump, so check for ABS codes as well.
Will P0503 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0503 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0500 | Vehicle Speed Sensor A Malfunction |
| P0501 | Vehicle Speed Sensor A Range/Performance |
| P0720 | Output Speed Sensor Circuit |
Guides that help
When it is more than a sensor
Sensor codes are usually fixed with a sensor, a connector, wiring or a leak repair rather than major parts. If testing turns up internal engine trouble instead, see how to tell if an engine is blown and compare engines by code on our engines page.
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