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ACC/PAS and High Beam Assist/Headlight Beam Adjust
Are the ACC/PAS and High Beam Assist/Headlight Beam Adjust systems connected somehow, like by the front sensor or camera? I have these messages popping up (was intermittent, now it's all the time) on my 2018 Base and have checked several things so far but am at a loss. I've also had a 'Check front right/left dipped headlight' message pop up a few times, though not at the moment. Here's what I've found so far:
fuses are intact, though the previous owner had the #43 Headlight Beam Adjust (5A) and #44 Seat Ventilation (7.5A) fuses switched around. I've since corrected this.
low beams work fine - verified that both adjustment motors are working (turning on the lights before turning on the car, turn car on, both lights do their dance)
high beams used to work, now they do not
battery seems fine, is between 12.5-13 volts at startup. This is the original battery
no codes show up on my ODB2 scanner
I just replaced all plugs & coils (had a coil fail on me so did them all). Above-mentioned errors still show up (have heard a bad coil can cause other issues, not in this case)
The auto start/stop works intermittently as well & has not worked since both of the above errors have become consistent
My concern is that the wrong fuse in #43 may have shorted something out but that's just speculation. Anything else I can check or that I may be overlooking?
I suppose I should've mentioned that the messages I'm getting are 'ACC/PAS Unavailable' / 'Headlight Beam Adjust defective' / 'High beam assist not available'. I've searched all over Rennlist and the internet & see that these have been issues but I haven't seen anything about how the systems are connected (if at all).
OBD2 scanners tell you diagnostic codes from the engine/emissions. As with just about every issue outside of an emissions problem, you need to get a scanner that can give you useful info. Otherwise you're essentially working through this blind!
A battery from 2018 is within the range of needing a replacement. The one in my 2017 GTS may be a candidate now, as I get periodic strangeness with the start/stop (which I almost never have activated).
A fuse being switched to a different value shouldn't make much difference, unless of course the fuse blew because it wasn't of a high enough value (or the wires fried due to too high of a value). But for 7.5 vs 5 it wouldn't seem like it'd matter.
ACC does use it's own front camera. The headlights use a sensor on the inside of the front windshield. I don't think they're related as on-coming headlight dip is available without the added ACC option.
When you say the high beams 'used to work' how are you checking? Do they light up when you put the lights into automatic high beam mode? You do this by pressing forward on the stalk and an extra icon lights up in the gauge (see the manual for specifics). You'd need to be driving, over 35mph, in the dark (without on-coming traffic) to check this. That'd at least tell you if the lights themselves are working or if it's a problem with the control stalk.
And do you have any indication there was front-end damage to it?
A battery from 2018 is within the range of needing a replacement. The one in my 2017 GTS may be a candidate now, as I get periodic strangeness with the start/stop (which I almost never have activated).
A fuse being switched to a different value shouldn't make much difference, unless of course the fuse blew because it wasn't of a high enough value (or the wires fried due to too high of a value). But for 7.5 vs 5 it wouldn't seem like it'd matter.
ACC does use it's own front camera. The headlights use a sensor on the inside of the front windshield. I don't think they're related as on-coming headlight dip is available without the added ACC option.
When you say the high beams 'used to work' how are you checking? Do they light up when you put the lights into automatic high beam mode? You do this by pressing forward on the stalk and an extra icon lights up in the gauge (see the manual for specifics). You'd need to be driving, over 35mph, in the dark (without on-coming traffic) to check this. That'd at least tell you if the lights themselves are working or if it's a problem with the control stalk.
And do you have any indication there was front-end damage to it?
When I first got the car (about 500 miles ago) everything worked. Headlights used to work manually from the stalk, now they do not. I still get notification in the HUD that they're on but there's no change in the amount of light being produced.
There's no indication of any front-end damage.
I purchased an iCarsoft v3.0 to get more details on the errors. All it says is 'no communication' with right headlight control unit, CAN safety, and front camera control unit. That sounds to me like a wiring issue which is what I was figuring before. Are the camera & sensor you're talking about located in the same area, directly behind the rear view mirror? That will at least give me a starting point to work from.
When I first got the car (about 500 miles ago) everything worked. Headlights used to work manually from the stalk, now they do not. I still get notification in the HUD that they're on but there's no change in the amount of light being produced.
There's no indication of any front-end damage.
I purchased an iCarsoft v3.0 to get more details on the errors. All it says is 'no communication' with right headlight control unit, CAN safety, and front camera control unit. That sounds to me like a wiring issue which is what I was figuring before. Are the camera & sensor you're talking about located in the same area, directly behind the rear view mirror? That will at least give me a starting point to work from.
Curious if you were able to resolve this. If so, how? Thx.
Curious if you were able to resolve this. If so, how? Thx.
Not yet but I'm getting close. I believe it's an issue in the connection between the front sensor and the wiring harness - I've disconnected/cleaned/reconnected (with an alcohol-based cleaner & dielectric grease before reassemble) 3 times now and each time everything works for a couple of weeks before failing again. There's no slop in the connection so I'm thinking either the wires are backing out of the connector or I'm not cleaning the connections well enough & there's some kind of build-up on either end.
It's a tough area to see what's going on (I don't want to remove the front sensor as that would require recalibration) but I'm pretty confident I can fix it. I'll keep ya posted!
I've had the problem stated above intermittently for a while now. This time I cleaned the connection as best I could without using additional dielectric grease (if you look at the photo, though it's blurry, you can easily tell there's already enough). I used a brush to remove as much as possible from the connectors - too much can actually be bad for electrical connections - and so far I haven't had any issues. It's possible that the previous tech used too much. I'll be driving about 1-2k miles over the next several weeks, we'll see what happens. Remove this connector by applying pressure on both sides and gently lifting up. Cleaned as much grease out of here with a small toothbrush. Should be okay to reapply grease to the sides of the connector but not on any metal surfaces (just like a spark plug boot).
It's been a few months & I've tried a few other things that seem to have "fixed" the issue.
Purchased the service manual. This was immensely helpful in identifying how the systems are related!
Checked all ground points (behind kick panels, behind tail lights, engine bay, etc.), all were in great shape.
Checked for moisture damage and/or splices in the wiring per this post. Removing panels and pulling the carpeting up was easier than I thought. I was surprised (based on the post) to find zero splices and zero signs of water damage. I checked connectors & relays for looseness - battery compartment was fine but I did find one behind the driver's side fuse box that felt loose. Not sure if it actually was loose or if I was trying to find something wrong but I did this with the ignition ON and the number of codes increased/decreased (all but the ACC/PAS codes were affected by this).
While I had the carpeting up and driver's seat removed I changed the battery (tested okay but it's 5+ years old). After registering the new battery I cleared out all codes/messages.
Zero issues since doing all of this (one week), we'll see if this takes care of the issues.
03-30-2023, 02:14 PM
ACC/PAS and High Beam Assist/Headlight Beam Adjust
