Has anybody taken apart the HCH dashboard to see what kind of interface the MPG display has?

This is definitely a strange idea, but what I would like to do is create a system that interfaces to some part of my '04 HCH so I can read the current value of the MPG display and display it on a large (5" x 7") L.E.D. dot-matrix numeric display which will be facing out of my rear windshield. I'd like to show off my great MPG rating to all the people that drive past me on the freeway.

The dot-matrix display will be the easy part (I have done many microcontroller projects like this), it is figuring out where to connect to my HCH and what the protocol is that will be the hard part. I don't know if this is even do-able, because I am sure Honda does not publish a detailed Chilton's (or similar manual) for the HCH that goes into this kind of detail. I was thinking that maybe there is someone lurking on this forum that might have some inside information? I'm guessing that Honda uses some sort of CAN bus network inside the car. Does anyone know details on this stuff?

Stephen

 

Its OBDII and it is published in hondas repair manuals. You can find obdII interfaces online and hook them to a computer and interface some kind of Screen to it.

However, I believe one user had an interesting solution in that they had a cheap camera pointed at the display and just captured it and displayed it on a screen he placed in the back of the car.

 

Whoa Stephen, if you succeed with this endeavor, you might want to replace your windows with bullet proof glass.

I can just see people shooting at you as they drive by.

Cool idea though.

 

Actually, I think that if he makes it work he can create a small business selling such accessories.

Another option might be to have a button on the dash that you press to change the LED display so it says BACK OFF when somebody's tailgating you (and then sell it with bullet proof glass)

 

If you pop the lid off of a scangage you'll recognize what you see immediately, and sending the display signal to an alternate display should be child's play, though getting just MPG to show involves some protocol work, as you mentioned.

I loaned mine out, but when I get it back I'll try to look at the specific designators involved.

 

I've often thought of this as well. But, I say let sleeping dogs lie. No need to create more road rage. There are too many "loose cannons" driving around with malintent these days, dudes on parole, sex offenders, politicians, drunks etc... Plus in some states, such as here in Taxachusetts, you would need to re-register your car with commercial plates to display any type of signage.

 

If you know that you can get signals from ECU's, such as injector and speed pulse,
my SuperMID M-1 will help you...

https://www.greenhybrid.com/discuss/...-t-1.3015.html

 

It's a cool idea that I've been toying with as well, but when I mentioned it to friends here in TX they all responded the same way: be prepared for some nasty action by other drivers. Even without such display, there are some drivers (mostly of giant SUVs and jacked up trucks) that have to show to you they don't care about mileage by pulling to within inches of your rear, or by cutting you off as close as they can as they pass (the same happened in my former MINI Cooper, another car that seemed to irritate a lot of SUV and truck drivers here in TX).

 

What Jerks!

 

Most people I have talked with about my hybrid say:

1. Well, just how much more did you spend to get better mileage and laugh.
Then I have to ask them how much did you spend extra to get that big old SUV when you could have bought a simple Kia for about $9,000 and it would have got you everywhere you wanted to go and saved $30,000.

2. Then they ask about power. Does it have any power?

3. They say they want a big car.

So, I say to each, his own and go about my business and dont worry about them. Dont think I would not want a display in my rear window if I were driving my HCH conservatively in front of them, slowing them down as is the case if you really go after high mileage!