Honda civic 2003 dashboard light yellow looks like a motor near the oil and battery warning lights has turned on. Could backing car up with gas cap open at station have caused this?

The yellow light you described is most likely the Check Engine light, which indicates a potential issue with your vehicle's engine or emissions control system. It is not likely that backing up with the gas cap open would cause this light to come on. There could be several other factors causing this light to illuminate. Here are a few possible reasons why the Check Engine light might have turned on:

1. Loose or Missing Gas Cap: While backing up with the gas cap open is unlikely to cause the issue, if the gas cap is not securely tightened or is missing, it can trigger the Check Engine light.

2. Emissions System Issue: The light may turn on if there's a problem with any component in the emissions control system, such as the oxygen sensor, catalytic converter, or exhaust system.

3. Faulty Engine Sensor: A malfunctioning sensor related to engine performance, like the oxygen sensor or mass airflow sensor, can cause the Check Engine light to come on.

4. Engine Misfires: If the engine is experiencing misfires, which occur when the spark plug fails to ignite the air-fuel mixture properly, it can trigger the Check Engine light.

5. Low Engine Oil: In some cars, a low oil level can turn on the Check Engine light.

6. Vacuum Leaks: A vacuum leak in the engine compartment can also cause the Check Engine light to turn on.

7. Computer Glitch: In rare cases, a temporary computer glitch or electrical issue could also cause the Check Engine light to come on.

Recommendation:

It is recommended that you take your vehicle to a qualified mechanic or an auto repair shop for proper diagnostics. The mechanic will use a diagnostic tool to retrieve the error code(s) stored in the vehicle's computer, which will help identify the root cause of the Check Engine light being on.