I want to reset the ECU of my MY98 by disconnecting the battery for about an hour. What happens to the (computerized) odometer? Is it reset to 0 miles as well or does it keep the mileage it had prior to the battery disconnection?

Cheers,
Ruud.

 

I would be exceedingly surprised if it reset the odometer, otherwise it would be exceedingly easy to clock the cars. Disconnecting the battery does appear to reset the trip counter however.

 

Is it just an hour to reset the ECU ???

Anything that doesn't get reset immediately has to have
a) a backup battery
b) non-volatile memory.

I would suggest that the ECU probably has A and the odometer has B.

My experience has been that backup batteries last for about a day in general.

let me know if it works..hey, we'll all be disconnecting over the weekend and thrashing on a monday morning !

 

I would be too, David.
But how does the odometer save its last reading then? Does it have its own battery?

And Lee: that's what I've understood.... that you only have to disconnect the battery for about an hour. The capacitor of the ECU will drain, the ECU gets out of power and loses its historical data. Anyone, please correct me if I'm wrong.


Cheers,
Ruud.

 

I know less about this than anyone else, but once you have disconnected to let the memory of all that 95 RON fuel to fade away, does it mean that you get the engine check light coming on, and have to then take it to a dealer to get it re-set ? please help

 

Does anyone know if the reset is neccesary with a 99MY? I did hear rumour that they have a new ECU that 'resets itself'

If so, I won't bother trying, as I'm too lazy to reset the radio channels again!

 

Lee,

I've had the battery disconnected for 2 hours yesterday and - after reconnecting - went out for a blast. I found that:
- the idle is smoother,
- the engine is running smoother during driving,
- the engine picks up a little bit better in the mid rev range (2500-5500 rpm), especially in 4th and 5th gear.

Of course, all of this is instinctive (no measuring done). After all how can you make sure that the ECU has actually been reset.


JWBTCC,

No side effects (no flashing 'Check Engine' light or so), just a reset TRIP-meter and a reset radio-setup. You can safely do this with your own Scooby.


Cheers,
Ruud.

 

Ok, I have a few thoughts to throw in. In regards to the ecu and losing stored codes and "learned" memory, the computer after a power loss, generally (as mentioned about a capacitor) discharges slowly until dead. It doesent however take much more than maybe 15 minutes. In regards to the odometer and its display of miles..it does use the same kind of Grandfather clock operation like cars of yester year. it has a series of "buttons" that are on each digit. as the speedo cable (sometimes electro magnet) spins, it turns small gears and they make contact with the assigned digit. they have 10 points each.1,2,3,4,5,6,7,8,9,0..(upto a million miles) and they count up just like the old ones did. except, they now do it on a digital display. it never looses this information until you mess with the odometers gears. a dead battery cannot mess up the actual reading, but its true that in the "trip odometer" is a memory type system like a house digital clock..loose power and it dies. Yes the ecu goes back to "unlearned mode" after prolonged power loss. It drives different because it has to "relearn" all the specifics..averages and the like. Air temps, pressures, driving styles etc etc. So this be known, its like a baby..new and untarnished. But, if there is trouble, baby will have you know in short order. Hope this clears up some things.
jeff

 

I had my ECU resetted last week by my dealer at Rotterdam because i had requested 98 RON at delivery but the had put in 95 RON. They only disconnected the battery for 2 minutes. The odometer didn't lose it's data, the trip meter and clock did. I got the impression that the ride was a little smoother afterwards but i'm not that sure because i was forced to use 95 RON within 400 Km!! At this moment i'm driving 400 Km/day at 160/180 Km/hour(stinger fitted)so i'm using a lot of gas and was running out not able to find 98 RON. I have to do the resetting again and find out.

 

Like all digitised odometers it has it own memory and battery back up. e.g. your computer runs on battery for its bios settings or else everytime you unplug the PC from the mains you would have to reset your bios.

Incidently for those affected by the CIH+ virus you have my symphaty, next year if you forget to run anti virus checker before 26th April I suggest you enter bios mode, change the date and run anti virus check. A mate of mine, among others, lost payroll database for 200 employees stored on abascus - thats a real bummer!