How to Determine if the Fuel Saving Switch is Faulty?
2 Answers
Use a diagnostic scanner to read the fault code. The fault code is: P0191: Fuel saving switch voltage signal unreasonable fault (current); etc. Check the circuit. While toggling the fuel saving switch, observe whether the status of the fuel saving switch changes through the data stream. After toggling the fuel saving switch and finding no changes, remove the fuel saving switch to check for issues such as loose connections, pin retraction, or corrosion. Confirm that the fuel saving switch is damaged, replace it, clear the fault code, and test drive the vehicle again.
When driving, I usually observe the car's response to determine if the fuel-saving switch is malfunctioning, mainly by checking changes in fuel consumption and driving feel. The fuel-saving mode is supposed to save fuel, but if it's broken, switching won't have any effect, and fuel consumption remains high. Last time on a long trip, I clearly switched to the fuel-saving gear, but the fuel gauge dropped as fast as in normal mode, which made me suspect the switch was faulty. I tried troubleshooting myself: after starting the car, I frequently switched modes to see if there was any difference in engine sound. Normally, there should be a slight reduction in noise and speed. I also checked if the dashboard indicator lights turned on and off properly. If there was no change or the lights didn't illuminate, the internal contacts might be oxidized. Finally, I gave the switch button a simple check to see if it was stuck, gently shaking it a few times. If that didn't work, I'd head to a professional shop right away, because driving long-term with high fuel consumption can damage the engine. Safety comes first—don't delay.
