Our trucks never sleep

[Prairie Dog]

During the recent work I did on the front end, I had the speed sensor at one wheel disconnected for several days but I never turned the key on during that time. After all the work was done, I started it up and had both the "Brake" and ABS lights stuck on. After I started to move backwards they both wen't off. How the heck did it know the sensor was out if the key was never on?

 

[Bernie]

... Have you read or seen Carrie?

But seriously, I have the same experience. I can only assume Can Bus systems are always "on". We all know there is a small draw on the battery when parked from the computer, and it would be safe to say this is what it is doing. Major changes (like dead shorts or open circuits) will re registered / reordered even when off. I guess this is important for some systems that may keep the truck from running / help the truck start (like temperature).

Probably from a programming technical standpoint easier to keep all of the sensors "awake" than just he ones needed for starting.

Just my speculation.

 

[Prairie Dog]

It sure must be doing something like that.

 

[JBallou]

05 and up is can-bus. Don't have any other good ideas for ya.

 

[Bernie]

Good point. I misspoke. I should have said the engine management (Can Bus or earlier versions).

 

[seafish]

05 and up is can-bus. Don't have any other good ideas for ya.

I think you mean 2006 and up??

The 2005 ECMs, while OBD2 compliant, are not can-bus wired. IIRC, they communicate to the various electronic sub-systems using some sort of earlier version of software protocol that is related to can-bus, but not can-bus.

For the life of me, right now, I cannot remember what that protocol was named.
(and NOT being able to actually rememeber the name bothers me more then I am willing to admit. )

can ANYONE help me out here... TIA!!

 

[Bernie]

I think you mean 2006 and up??
For the life of me, right now, I cannot remember what that protocol was named.
(and NOT being able to actually rememeber the name bothers me more then I am willing to admit. )

Wasn't all that early communication network stuff RS232 with different protocols? I remember reading about the NGC3 (or something like that for next gen communication series 3 or something). But that wasn't the data, just the means for moving it around.

I think for the data on early pre OBD2 there are a handful of protocols that are industry wide (a couple of them are something like J1850, and then is four our five different ISO standards). I don't remember them specifically, because if I remember correctly there were a lot of variations from manufacture to manufacture, and model to model.

OBD2 and Can Bus certainly simplified things a lot.

I know I didn't answer your question, but I thought maybe that might jog your memory.

 

[cerberusiam]

The earlier protocol is EOBD. All these trucks have monitors active on certain things when the key is off. Thats why they ship from the factory with a fuse out so they don't kill the batteries.

 

[seafish]

The earlier protocol is EOBD.

cerbusiuam, that's it, "eobd", THANK YOU!!!





Does that stands for electronic, on-board, diagnostics ???