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Discussion Starter #1
Hi everyone! Today while my wife was driving in the parking lot, the Volt red-light on the dashboard starting flashing and the car just briefly slammed its brakes. She was surprised, not seeing any threat. My questions to you:

1)Any idea what would cause this (faulty camera, sunlight)?

2)At what speed does the auto brake feature kick in? Could it happen at high speeds?

Thanks!
 

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I'm not sure about it, but I will add that I was stopped at a red light today, and the forward proximity alarm went off. (The alarm that sounds when you park too close to something.) Nothing in front of the car, and it cleared up after a second.

I don't know if the low-speed forward automatic braking uses the ultrasonic system and the all-speed FAB uses the adaptive cruise radar, but if that's the case, it could have been a phantom ultrasonic sensor hit. Could bug guts or dirt cause such anomalous readings? I haven't checked my front sensors yet.
 

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You are on the right track with possible causes...this happened to me once driving on the 805 in mid afternoon sun going under a bridge with wooden tressels (bridge construction) that broke up the sunlight and I think that was the cause of my forward collision alert being activated. Has only happened that one time. Always keep the windshield clean, particularly where the camera looks through. Same for the front grill if you have ACC.

In my case it was only the alert, the 6 red dots displaying on the windshield, not the active braking. Forward Automatic Braking (see page 210 of the manual) only works between 5MPH and 37MPH. I was going in excess of 37MPH on the freeway of course so it didn't activate FAB. In the parking lot, your wife was most likely in this speed range. Again, even the manual suggests keeping that windshield clean as one way to avoid unwanted activations.
 

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I don't know if the low-speed forward automatic braking uses the ultrasonic system and the all-speed FAB uses the adaptive cruise radar, but if that's the case, it could have been a phantom ultrasonic sensor hit. Could bug guts or dirt cause such anomalous readings? I haven't checked my front sensors yet.
FAB uses the camera, not the radar (page 136). Yes, bug guts and dirt/grime on the sensors around the car could cause false warnings. Keep it all clean, all the time. Help the Volt Help You, like Jerry Maguire.
 

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FAB uses the camera, not the radar (page 136). Yes, bug guts and dirt/grime on the sensors around the car could cause false warnings. Keep it all clean, all the time. Help the Volt Help You, like Jerry Maguire.
Interesting. Good to know. I had assumed the camera was solely for lane keep assist, but it apparently does a lot more.
 

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I've gotten alerts a few times (usually in bad weather) that the forward collision system was unavailable. Always seems to clear up on its own. I have also seen the sensors get tripped up by heavy reflections from sunlight but not very often.

I recall reading some threads here that the mounting of the front license plate bracket (if not in the correct spot) can cause the collision sensors to get tripped up.
 

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Discussion Starter #7
Thanks much for your responses. What's baffling I cleaned the car on Saturday, very few bugs. The only thing I could think of was the sun or some type of reflection. I think if that were to happen at 35mph in California you would almost certainly be rear ended.
 

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My ELR applied (not slammed) on the brakes once because of headlight reflection on a metal construction plate going across the road. Only time it happened to me in either Volt or ELR.

ELR doesn't brake that quickly (like hitting the anti-lock) the driver has to take over. FAB on ELR is warned in the manual that it is to 'lessen the impact' not completely avoid a collision.

I use ACC a lot for commuting and that braking algorithm is much smoother. It does get confused if someone jumps into the gap and slams on their brakes. The human can see incoming better than ELR can. ACC definitely IS NOT robo-driving.
 

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Near my house there is an expansion joint between the road and a bridge. It's a pretty good bump, but not so much that you can't take it at speed (45). My last car would consistently think that was something in the road, and beep and flash the warning light at me. Before it hit the brakes I was either past it, or the angle changed enough that it no longer "saw" it.

Only once or twice in the last 10 years have I had the brakes actually get applied (in addition to all the lights and beeps) without my thinking it was necessary. It is startling to say the least, but usually only very temporary since whatever the car "saw" was of no concern to me and obviously quickly cleared up.
 

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I get the occasional false alarm on the interstate when going under a bridge (as was already mentioned). However, it just flashes the lights. Seems like GM has their stuff more sorted than most (many other makes are quite trigger-happy from what I read), but you'll still get the odd false alarm. That said, in every emergency braking situation I've faced so far, the car was on the brakes before I was...even when I was watching it unfold in front of me (knowing something could happen). So I've been quite impressed with the systems.
 
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