Mercedes SL throttle valve issue

A defective throttle valve on a modern Mercedes-Benz can manifest that way. Reduced engine power and the check engine light are consistent symptoms. The throttle sensor regulates air intake, and any malfunction disrupts the balance needed for performance. Before replacing the valve, have you inspected the wiring and connectors for corrosion or damage? A loose connection can mimic a failing sensor. Have you checked the specific diagnostic trouble code (DTC) reported by the engine control unit (ECU)? The code can provide insight. What is your technical background?

I'm comfortable with basic car maintenance. I checked the wiring and connectors – didn't see anything broken, but I didn't go deep. The code was P0121, which confirms the throttle position sensor issue. What else should I be looking for, and is there any chance this isn't the throttle valve itself?

The P0121 code suggests an issue in the throttle position sensor circuit. The fault could be from a wiring harness or a malfunctioning engine control unit (ECU), but that is less likely. Given your expertise and the potential for unintended consequences, it would be wise to consult a qualified technician. The replacement cost you mentioned aligns with past costs.

I appreciate the advice. I was hoping to avoid a big bill, but it sounds like this is beyond me. I'll take it to a mechanic. Looks like I am looking at a repair costing around 265€. Thanks!