Which sensor does what ?

[ColinB]

Having experienced a minor glitch with the operation of some of the electronics in cold & damp weather (see this: http://clubjazz.org/forum/index.php?topic=8887.0) I thought I'd try to work out which sensor fed which system so I'd know which ones to be wary about in similar conditions in future. The handbook describes various warnings you're supposed to get if any of these sensors are obstructed in any way, but I didn't get any of those, it just became clear as I drove that some of the systems weren't functioning correctly. The one that worries me is the City-Brake Active system, which can apply the brakes unexpectedly.

After browsing the handbook for a while, the best I could come up with is in the attached picture (page nos. refer to the handbook, note the handbook illustrations appear to be for LHD car). So, if the handbook is correct, there are two sensors in the pod that Honda aren't telling us about. Or the handbook is wrong. I tried asking my local dealer, but the best they could offer was that the City-Brake Active system uses a radar sensor concealed behind the Honda "H" in the grille ... I can't see any evidence for this, and if it's correct then the handbook is even more wrong.

Anyone able to correct my picture, or know of a definitive source of info ?

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[Skyrider]

I think 2 & 4 in your photo  are separate sensors, one an ambient light sensor for the auto lights and a wet screen sensor which reflects UV light from the screen surface and detects distortion if it is wet.

[ColinB]

Correct, they are indeed separate sensors. As far as I can tell from the tiny picture in the handbook, it seems to show #2 doing both jobs. So you reckon #2 is the rain sensor, and #4 is the light sensor ? Makes sense. #5 seems to be a mystery, unless maybe it's part of the laser ... maybe #3 transmits, #5 recieves ? Bit odd that the handbook doesn't exhort you to keep it clean.

[Skyrider]

I don't know which is which but would guess based on other cars I have owned that 2 is light and 4 is rain. You could check by putting some tape over them one at a time to see when the lights come on.

[guest1372]

2&4 and 3&5 look like they are one unit with separate TX and Rx windows.
A Time-Of-Flight laser ranging sensor normally has two windows, they might be calling it radar instead as a more universally understood concept.
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TG

[ColinB]

Thanks for the inputs folks.

A Time-Of-Flight laser ranging sensor normally has two windows, they might be calling it radar instead as a more universally understood concept.

Handbook definitely refers to it as a laser, so I guess it makes sense for #3 & #5 to be Tx/Rx for the same system. Seems to me this is the really important pair to keep clean, because this system can actually control the car by applying the brakes without driver intervention. All the others can be over-ridden manually or ignored if they misbehave.

2&4 ...  look like they are one unit with separate TX and Rx windows.

Not sure I understand why rainfall & light sensors need Tx/Rx components, but I will admit I don't know a whole lot about how these sensors work. If I get bored sometime I'll try blocking them individually to see what happens.

[Skyrider]

The wet screen sensor is a tx / rx device, it shines an infra red light onto the screen and detects distortion in the reflection if the screen is wet.