I’m a fellow Mercedes-Benz enthusiast and like you, I’ve experienced the usefulness of an Actron Obd2 Scanner. It sounds like you’re in a similar situation to one I recently encountered with my 1998 W210 E320. My Actron CP9135 scanner was great for diagnosing a misfiring ignition coil, proving its accuracy and ease of use. However, like you, I ran into a snag when the ETS and ABS lights started appearing, especially during turns.
You’re right to suspect common culprits like the brake light switch, battery voltage, wheel speed sensors, or steering angle sensor. And your research in the archives correctly points to the importance of reading the fault codes to pinpoint the issue. The problem you’re facing, “no Faults Detected” on your Actron scanner, is a common limitation of basic OBD2 scanners.
To answer your questions directly:
(1) Do I need a different scanner for ETS/ABS codes? Yes, most likely. Your Actron CP9135, while excellent for generic OBD2 codes (powertrain related issues), may not be capable of reading Mercedes-specific codes, particularly those related to the ETS (Electronic Traction System) and ABS (Anti-lock Braking System). These systems often communicate using protocols beyond the standard OBD2, requiring a scanner that can access Mercedes-specific diagnostic information. You’d need a scanner that specifies compatibility with Mercedes-Benz systems and ABS/ETS modules to retrieve these codes.
(2) Should I use my scanner to reset IM Readiness functions? Generally, resetting IM Readiness functions is used after repairs to clear codes and prepare for emissions testing. In your current situation, it’s not directly relevant to your ETS/ABS light issue and wouldn’t help diagnose or resolve it. Focus on getting the correct codes first.
(3) Could a faulty brake light cause ETS/ABS lights? Absolutely. A malfunctioning brake light, especially due to grounding issues as you describe, can indeed trigger ETS/ABS lights. The electrical system in modern cars is interconnected, and issues like this can confuse the system. A faulty brake light circuit can interfere with signals to the ABS/ETS modules.
(4) Should you replace the stop light switch again? It’s possible, even though you tested the new switch. While your testing was thorough, a faulty switch could still be intermittent or have issues under vehicle operating conditions. Given it’s a relatively inexpensive part and crucial to the brake/ETS/ABS systems, replacing it again might be a worthwhile step, especially since you’re experiencing brake light issues.
It’s understandable to miss the simpler days of older Mercedes-Benz models. However, modern systems like ETS and ABS are critical for safety. To effectively diagnose your ETS/ABS lights, I recommend seeking a scanner that reads Mercedes-specific codes or consulting a mechanic with access to professional-grade diagnostic tools. This will allow you to accurately read the fault codes and address the root cause of your issue.
