BMW M4 Limp Mode: Temp Sensor Causing Power Loss

Hi there! I've got some experience working with BMWs since I had a similar issue with my 2016 BMW M2. Nothing too complex, but I know my way around basic maintenance. Had almost identical symptoms, limp mode, CEL, and terrible fuel consumption. Turned out there was an exhaust leak near one of the temp sensors, which was causing false readings. Took it to my trusted workshop, and they found a crack in the exhaust manifold that was letting gases escape. They fixed the leak and replaced the sensor, cost me about 265 Euro total. Car's been running perfectly since then. Before I share more specifics, could you tell me if you're getting any particular error codes? Also, have you noticed any unusual exhaust sounds or smells? These details would help me understand if you're dealing with the same issue I had. By the way, might be worth checking if there's a service campaign for your M4, sometimes these issues are known to BMW and might be covered under warranty.

Thanks for sharing your experience! My M4 isn't throwing any specific error codes through my OBD scanner, but I've noticed a slight rattling sound from the exhaust area, especially when cold. Just had my service done last month at 60912 KM and everything else was good. No unusual smells though, which makes me think it might be just the sensor playing up rather than a full exhaust issue. But I'll definitely get it checked out by my mechanic, particularly around the exhaust manifold area based on your experience. Really helpful info about the potential warranty coverage too, gonna look into that!

Hey again! Back with more info about my M2 situation since you mentioned that rattling sound. Yeah, that rattling noise when cold is super familiar, had the exact same thing with my M2 before the whole sensor drama. Initially thought it was just the sensor too because my car was running fine otherwise, just like yours. But here's what I learned: that rattling noise was actually my first warning sign of the exhaust manifold issue, not just a sensor problem. Here's a pro tip from my experience, even though your service was recent, these issues can pop up pretty quickly. When my mechanic did a deeper dive, they found that the manifold crack was causing that rattling sound, and it was messing with the sensor readings. The crack was tiny at first but got worse over time. Since you're at 60912 KM, you might still be under warranty. Mine was just out of warranty when this happened (bad timing, right?). If I could do it over, I would've had it checked immediately when I first heard that rattle, might've saved some cash. Let me know what your mechanic finds. Would be interesting to see if it's the same issue. These BMW sensors can be tricky, but better to catch any problems early!

Thanks so much for all this detailed info! That's really concerning about the rattling being an early warning sign of the manifold crack. You've convinced me to take this more seriously, gonna call my mechanic first thing tomorrow instead of waiting it out. You're right about catching it early; I'd rather deal with it now than risk bigger problems. Definitely appreciate the heads up about checking for warranty coverage too. Just checked my paperwork and I've actually got about 8 months left on my extended warranty, so that's a relief! Going to document that rattling sound with a video before taking it in, just to have everything properly recorded. Really glad I asked about this here, your experience with the M2 has been super helpful. Will update once I know what's actually causing the problem. Thanks again for taking the time to share all this!