[JABCAT]

About 3 hours into my 3.5 hour drive today I was coming up on interstate traffic with the ACC activated when my car started accelerating instead of braking. The ACC was set at 78 mph and the car accelerated to 84 mph before I slammed on the brakes. The ACC had worked normally the entire drive up to that point. Once traffic opened up I hit the resume button on the steering wheel and a warning message popped up in the cluster & on the screen that said "you can continue driving. Check sensors or clean them" It also had a picture of the front of the car with a red square covering the area of the sensor.

Has anyone had this message pop up before? It did rain yesterday & this morning so the car is dirty, but that's the first time I've seen that message in 20k mi. I would also think if the sensor was dirty/obstructed it should have popped up a warning at some point when I was driving? The acceleration above the set speed limit is also concerning.

[BroDoze]

So was the radar sensor dirty?

[JABCAT]

Originally Posted by BroDoze

So was the radar sensor dirty?

Based on the image showing the sensor blocked I thought maybe a piece of road debris, like a plastic bag, had gotten sucked up into the grill opening maybe covering the sensor. There was nothing blocking the sensor & it wasn't excessively dirty.

Even if it were, that wouldn't explain the vehicle accelerating well over the set mph.

[RockCrusher]

Some trash -- leaf or something -- could have gotten on the sensor and remained long enough to trigger the sensor blocked warning. Then just as suddenly as it ended up on the sensor it was removed.

The acceleration is a bit of a puzzle. Giving the benefit of the doubt to the electronics (rather than you... sorry) I'm wondering if perhaps you inadvertently hit the increment button?

To be sure from now on you need to be on high(er) alert for this anomalous behavior. If it happens again to me that would justify having the car in to the dealer service department for this.

[JABCAT]

Originally Posted by RockCrusher

Some trash -- leaf or something -- could have gotten on the sensor and remained long enough to trigger the sensor blocked warning. Then just as suddenly as it ended up on the sensor it was removed.

The acceleration is a bit of a puzzle. Giving the benefit of the doubt to the electronics (rather than you... sorry) I'm wondering if perhaps you inadvertently hit the increment button?

To be sure from now on you need to be on high(er) alert for this anomalous behavior. If it happens again to me that would justify having the car in to the dealer service department for this.

I thought that as well (leaf, trash, etc.), but I tried it multiple times after that incident & the same message popped up each time. Re: accidentally hitting the button, I didn't. My hand wasn't near that part of the steering wheel at the time. The set speed still displayed 78 mph on the HUD, even after I hit the brakes. If I would've hit the button, the set speed displayed would've increased.

This has happened at least 3x that I recall where the car failed to initiate braking when approaching traffic; however, this is the first time I noticed the car actually accelerate. It's going in for an oil change next week & I'll mention it along with the persistent "emergency call system inoperable" message. I'm confident it will be one of those "cannot duplicate customer concern" situations.

[TallGibbs]

Originally Posted by JABCAT

I thought that as well (leaf, trash, etc.), but I tried it multiple times after that incident & the same message popped up each time. Re: accidentally hitting the button, I didn't. My hand wasn't near that part of the steering wheel at the time. The set speed still displayed 78 mph on the HUD, even after I hit the brakes. If I would've hit the button, the set speed displayed would've increased.

This has happened at least 3x that I recall where the car failed to initiate braking when approaching traffic; however, this is the first time I noticed the car actually accelerate. It's going in for an oil change next week & I'll mention it along with the persistent "emergency call system inoperable" message. I'm confident it will be one of those "cannot duplicate customer concern" situations.

I wonder if there is a way to request the dealership pull telemetry data to verify the condition (setpoint of 78 mph, actual speed above that, accelerator position, radar sensor distance output, etc)?

[jmg]

You have been having ACC issues for awhile. I've been using ACC to test out the system since I got the car. Now at 1200 miles I haven't noticed any anomalies.

Personally, I think it's your grill protector. I would take it out and give it a try. There are kits you can cut out the grill to not cover the ACC sensor.

[JABCAT]

Originally Posted by jmg

You have been having ACC issues for awhile. I've been using ACC to test out the system since I got the car. Now at 1200 miles I haven't noticed any anomalies.

Personally, I think it's your grill protector. I would take it out and give it a try. There are kits you can cut out the grill to not cover the ACC sensor.

I've had the same issue with & without the protective grille installed (one without & 2 with). That definitely doesn't rule out the protective screen, however.

Of the kits I've seen that go around or behind the ACC sensor, they all have larger openings than the ZunSport. Even with the ZunSport installed, my radiator is still taking a beating from small pebbles.

[JABCAT]

Did my drive up from Austin to Dallas again and had the ACC flash the same warning and say cruise control unavailable, check sensors. I noticed when it happened it was in the exact same location on the Dallas North Tollway as when it happened the previous time. Sunny day, nothing obstructing the sensor, and 2 miles up the road I was able to re-activate the ACC.

[Scrutineer]

Originally Posted by JABCAT

Did my drive up from Austin to Dallas again and had the ACC flash the same warning and say cruise control unavailable, check sensors. I noticed when it happened it was in the exact same location on the Dallas North Tollway as when it happened the previous time. Sunny day, nothing obstructing the sensor, and 2 miles up the road I was able to re-activate the ACC.

Weird and interesting. At the problem spot on the tollway, is there an external sensor like an overhead toll reader or something else that may be disturbing the ACC?

Same location suggests something like that, no?

[JABCAT]

Originally Posted by Scrutineer

Weird and interesting. At the problem spot on the tollway, is there an external sensor like an overhead toll reader or something else that may be disturbing the ACC?

Same location suggests something like that, no?

It was about 1/4 mi before a toll reader & when it happened the car was accelerating after the car in front of me moved out of my lane (which is maybe the same as when it happened before I noticed the car accelerating).

I have experienced weird things with the electronics in this vehicle. I drive the same route every week down & back. Traveling South, there are two spots where my screen consistently goes black & CarPlay stops showing on the screen. It keeps working (music & navigation), but the CarPlay screen is black & stays that way unless I reset iDrive. However, traveling North, I drive through those same locations and have no issues with the screen/CarPlay.

With the ACC issue, no problems traveling South through this location, and no issues traveling North until these last 2 times. It's definitely strange.

[aerobod]

Originally Posted by JABCAT

It was about 1/4 mi before a toll reader & when it happened the car was accelerating after the car in front of me moved out of my lane (which is maybe the same as when it happened before I noticed the car accelerating).

I have experienced weird things with the electronics in this vehicle. I drive the same route every week down & back. Traveling South, there are two spots where my screen consistently goes black & CarPlay stops showing on the screen. It keeps working (music & navigation), but the CarPlay screen is black & stays that way unless I reset iDrive. However, traveling North, I drive through those same locations and have no issues with the screen/CarPlay.

With the ACC issue, no problems traveling South through this location, and no issues traveling North until these last 2 times. It's definitely strange.

Is there a radar installation near that location, such as at or near an airport? They can cause ACC and wifi connectivity issues (causing Car Play issues). Everytime I drive to the Rad Torque Raceway and pass by Edmonton Airport I have Car Play issues for a kilometre or so on the north bound lanes that are further from the airport and for about 2 kilometres in the south bound lanes that are about 200m closer to the airport.

[JABCAT]

Originally Posted by aerobod

Is there a radar installation near that location, such as at or near an airport? They can cause ACC and wifi connectivity issues (causing Car Play issues). Everytime I drive to the Rad Torque Raceway and pass by Edmonton Airport I have Car Play issues for a kilometre or so on the north bound lanes that are further from the airport and for about 2 kilometres in the south bound lanes that are about 200m closer to the airport.

Interesting suggestion, so I looked at the map. There is a small airport near where this has occurred.

[aerobod]

Originally Posted by JABCAT

Interesting suggestion, so I looked at the map. There is a small airport near where this has occurred.

The National Weather Service lists Addison Airport (ADS) as having a weather radar, not sure what equipment or frequency it is operating on, but certainly wifi frequencies can be overlapping with C-band weather radar. Not sure what equipment could interfere with the 77GHz ACC radar.

Typical ground-based weather radar can operate with a power output 10,000 times or more than that of automotive wireless and radar systems, so can cause interference, even if not in the exact frequency range.

[Bimmer Frank]

Heh, this has turned into a really interesting thread.

Modern electronic car tech vs real world existing technology...

We would have never imagined this in the 'analog' world.

[RockCrusher]

Originally Posted by JABCAT

I thought that as well (leaf, trash, etc.), but I tried it multiple times after that incident & the same message popped up each time. Re: accidentally hitting the button, I didn't. My hand wasn't near that part of the steering wheel at the time. The set speed still displayed 78 mph on the HUD, even after I hit the brakes. If I would've hit the button, the set speed displayed would've increased.

This has happened at least 3x that I recall where the car failed to initiate braking when approaching traffic; however, this is the first time I noticed the car actually accelerate. It's going in for an oil change next week & I'll mention it along with the persistent "emergency call system inoperable" message. I'm confident it will be one of those "cannot duplicate customer concern" situations.

A little late with a reply but yeah, I think the behavior warrants having the car in.

[JABCAT]

Originally Posted by RockCrusher

A little late with a reply but yeah, I think the behavior warrants having the car in.

Is this something they could check with a scan? If not, it's going to be "cannot duplicate customer concern" as it's so random.

[JABCAT]

A little more info. It appears that a hard acceleration while the ACC is activated may be causing the error. This morning I was behind a van on the interstate that had slowed to 20 below the speed limit with no vehicles in front of it. As the car began to slam on the brakes to slow, I changed lanes and accelerated quickly as other traffic was moving fast. The warning immediately popped up & the subsequent warnings of "cruise control cannot be activated" for the next few miles before I could activate it again.

Here's the warning that pops up below. If anyone else wants to test this out to see if they can trigger this warning to help determine if it's supposed to occur or if my car is having an issue, that would be a good test.