Today, when i was normally driving my car, my R56 JCW cabin temp sensor dropped to -40F, after a while, the coolant temp start to shoot up, and the check engine light came on! A little smell in the engine like burned rubber. Check engine light won't turn off and when I start the car, the coolant temp shoots and check engine light automatically on.

 

There is no weird engine noise, or any noise whatsoever, but this is scary.

 

If it is reading -40 inside i do believe that there is an issues with your Ambient temp sensor that should be located in your front bumper, wiring connects behind passenger fog light. have you scanned it, if so, what codes.

 

Check the connection and wiring
to the ambient temp sensor
(sensor is behind front lower grill
and can probably access the
connector to its wire from the
lower circular access panel at the
right (passenger) wheel well.
an open circuit will show a
-40 reading.

looks like Jason just beat me to this

 

I haven't checked yet, but I do believe something more critical is wrong. Or there won't be an explanation for the engine light and coolant temp increasing 1 degree every second and does not end

 

If a sensor drops out, the control system will try to compensate. If that sensor is critical to a certain control loop, such as engine coolant temperature control, that loop will no longer be in control. The CEL will illuminate because the sensor went out, the ECU will try to control but can't, and who knows what else will happen.

If I were you, I would pull the codes, and plan on NOT driving the car until its fixed.

 

If it where me, I would have already had the passenger side up on a Jack, front wheel off, and had the inner liner pulled back from the strut forward. From there access to everything, can get to sensor from under the bumper and now that it is in the air, and the connection for it is back there. I’d say maybe 1/2 an hour worth of work, but I have been in and out of this car enough. Hell swapped my intercooler in 30 minutes without jacking her up.

 

The sad reality is this happened when I drove to the office this morning, now I am 15 miles away from all my tools. :(

 

Is the car a GP2, as your user name would suggest? If so, you can access the ambient temp sensor by removing the fog light access panel in the passenger side wheel well. A quick check there will tell you if the sensor went AWOL or not. If so, there's your problem....

 

For one that sucks, I carry probably way too many tools, but is there really such a thing? Also carry a spare dv, oil, coolant, brake fluid.

 

Yes, it is a GP2 ! I will be sure to check that. Wow, that just made the process 100 times easier. Should I just use my panel removal tools to get it open? Luckily I have that in the car.

 

if it’s like mine it just turns to the left to remove and to the right to lock back in.

 

Update on the issue, apparently, a rat chewed up my ambient temp sensor wire, got it fixed at a random shop. No more engine lights. But seems like after the repair, when I rev the engine now, once in a while it stuck at 2000rpm for 2 seconds even when my foot is off the accelerator. it goes up fine, to 3k 4k rpm, but if I rev to 2k, it can cause this extremely strange issue, the engine also sound different when stuck, it sounds like this Porsche gt3 when launching. For a moment I thought the car was launching lol! This is what it sounded like ---

 

just adding some context, engine oil was changed one month ago, ceratec was added. so It should be fine. right before the repair, obd did pick up a cylinder 3 misfire code, but doesn't exist after temp sensor repair.

 

Glad you found the issue! Stinks that something else popped up… maybe another wire was nibbled somewhere?

 

Sounds like you might need to take the wheel off and the liner and see what else the rat chewed on.