I was on a long trip using radar cruise which worked fine most times except for the following.

1. I engaging the Radar cruise after using it on and off for 100's of miles then suddenly the car almost rear ended the car in front of me but I braked manually to prevent it. I figured out that the car would not allow me to set a distance to keep between the car in front. I played around with it and got a message something like "distance not available consult owners manual for conditions that can cause this" ? I didn't find anything. The next day I drove it and everything worked fine.

2. A few times I would set the speed I wanted and the car kept the speed 1 MPH lower than what was set and it continued that way at the lower speed for miles on different grades and with or without cars in front of me. Eg if I set it on 80MPH the car would keep it running at 79PMH and if I wanted 80MPH I had to bump up the setting to 81MPH. It did this at other speeds as well. The other times it worked correctly.

Has anyone experienced either of these 2 things or know what may have caused issue # 1?

 

Mine does the same, 1 mile per hour does not bother me. It works great.

 

On our first interstate highway trip, shortly after buying our 500h, I noticed that the speedometer was 'optimistic', and read higher than actual speeds based on GPS (and thus, the cruise set speed needed to be greater). Recently, it seems more accurate, don't ask me why.

I have also noticed that you cannot change following distance at speed. You need to be going slow or stopped.
Following distance (based on the bar display in our HUD) defaults to 3 car lengths, but has the capability of being between one > four car lengths.

 

Can't change the following distance while the cruise is in use? I could swear I have done that, will check next trip.

 

You need to be going slow IIRC.

 

When it's engaged and functioning properly I can change it at any speed. Something glitched and it said distance wasn't available.

 

Interesting...I remembered adjusting it in the past, but two weeks ago I couldn't until the next trip.


TOO MUCH ELECTRONICS?

 

I adjust mine easily at all speeds from 1-85 all day long no problems.

 

Same issue.. I can't seem to change the follow distance car length.. Yet it shows I can if I push the steering wheel button on the right button with the squares.. But nothing happens..

Where I really would like to use this is while using traffic jam assist.. as everyone keeps driving around me as there's almost four car links it seems

 

Just a guess... maybe the distance can be changed while cruise control is active, but not while the cruise control is actively pacing a car.
I'll experiment next time I'm on the highway.

 

If you have the cruise set to "normal" cruise control instead of "adaptive" distance is not available. (experience talking here lol, I've done it)

 

True about the normal mode.

I tried this just now - distance adjust works fine under all circumstances - slow, fast, tracking a car, etc. Are you sure you aren't trying to adjust the distance using the up/down arrow? The adjustment is a single button that cycles through the range of distances in one direction only with each push.

 

No, I was using the button at 9 o clock position on the heads up display. It worked fine for about 500 miles then the option stopped working and said no distance available. The next day it worked fine.

 

Just did a long road trip - all the auto features worked great. I keep my distance at two car lengths.

 

Maybe something from the road obstructed the forward radar sensor?