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Discussion Starter · #1 ·
I have a 2017 Q50 RedSport. The cruise control sucks. Sometimes when I go to use it will not turn on. If I continue to try and set it it will go into malfunction mode. It seems as if it is worse in the summer months than winter. I live in AZ so it gets very hot here. I have taken it to two different dealerships and they have yet to figure it out. I have had the computer replaced and nothing. Has anyone else on the forum had the same issue and were they able to get it fixed? Any help is appreciated. I have a picture of the dash after it goes into malfunction mode. I do have the adaptive cruise control on the car.
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Discussion Starter · #7 ·
I can't see the rest of your instrument panel, but do you also see this on the speedometer dial?

View attachment 109080

If not, and lacking any current DTCs to go on, I'd suspect there is a problem with the DCA (Distance Control Assist) system, which apparently you have since you indicate you have ICC (Intelligent Cruise Control) and they are both part of the Technology Package option for your model year. DCA uses the same radar sensor in the front of the car as the ICC, FEB, and PFCW. If there is a malfunction of the DCA system, then you will see the warnings that you posted above.

You said a dealership replaced a computer. You might ask them if that was the ADAS control unit they replaced.

You also mentioned that this appears to be high temperature related. Another possibility is the ICC radar sensor temperature is too high and the fail-safe when that happens is ICC, DCA, FEB, and PFCW are cancelled. I suspect this is a temporary DTC that clears once the ICC temperature drops to an acceptable level. If you have an OBDII scan tool (which every car owner should), the next time the malfunction alert comes up on your information display, scan the car immediately BEFORE shutting off the engine. If DTC C1B85 is displayed on the scan tool, that indicates an abnormal ICC sensor temperature. Once the ICC sensor cools down, the DTC should clear itself.
 

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Discussion Starter · #8 ·
This are the views of the dash. Not sure if this will help or not. So if it is the ICC temperature being too hot, is there no fix for this? Why do I not see on the forum other people having this problem. I would have thought by now the dealership(s) could have figured this out.
 

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Discussion Starter · #13 ·
Hey...I'm just spit balling here. Diagnosing problems like this remotely is conjecture. I only know what I'm told or shown.

I just noticed an outside temperature of 74 degrees with the car running at 40 mph and the warning is still there so I'm not so sure this is a heat-related problem with the ICC sensor.

Your instrument panel is showing the FEB warning light indicating that the FEB system is off due to a malfunction of the FEB system.

View attachment 109139

Your instrument panel also is showing the ICC system warning for the fixed speed cruise control mode.

View attachment 109153

The front sensor warning is also being displayed. All three of these are yellow, so one would suspect a problem with the ICC sensor or possibly the ADAS control unit. You said they changed a computer but I don't know if it was the ADAS they changed or some other control unit. Did the dealerships rule out a bad ICC sensor?

It would be helpful to have the car scanned with an OBDII reader and post any current DTCs displayed. If you don't have a scanner, take it to a car parts store that will scan your car for free. I can't offer any more insight without that information.
I have a ODB scanner on order. Good catch on it not being overly hot that day. I did not notice this. I dug up the old receipt and the computer they replaced had nothing to do with this stuff. It was the main display screen for the radio etcetera that was malfunctioning.
 
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