davidschneider1

Mercedes GLS Diesel Preheating Issue

Has anyone experienced issues with the ignition system or car electronics on a 2017 Mercedes GLS diesel, specifically concerning the preheating unit? The engine preheat indicator lamp doesn't extinguish after starting. The check engine light is on, and I see exhaust smoke when accelerating. Diagnostics point to a defective preheating control unit, maybe a fault in the cable or plug connection. The diagnostic report estimates a 95€ repair.

4 comment(s)

Sounds like a bad connection is plausible given the symptoms. Did you check the voltage at the preheating unit connector? Is it consistent with what the car electronics are expecting?

Regarding voltage consistency, what's the expected voltage range at the preheating unit connector for this Mercedes GLS model? Is there a recommended procedure for verifying this parameter, ensuring accurate assessment?

I don't have the exact specs for your car, but a multimeter should do the trick. If the voltage is erratic, it's likely the cable or plug you mentioned. It might be best to let a workshop handle it.

Your assessment aligns with my initial suspicion of a defective part within the cable or plug connection. I engaged a certified workshop for diagnostics and component replacement. The preheating unit was replaced, resolving the preheating lamp issue, check engine light, and exhaust smoke. Thank you for your input.

Join the discussion now: