I recently changed the battery in my 2005 Mazda 6 and got two surprises: the idle is erratic and the temperature is no longer showing. Based on the fact that the engine is controlled by a computer, I'm guessing that the idle somehow got "reset". As far the temperature not showing, it might be possible that the batterya different volatage (even though the battery was sold to use with my vehicle). I read, on the Internet (not always reliable), that the idle will go back to normal after a few days because the ECU makes "adjustments" that restore the idle to astable state (meaning not bouncing up and down). Has anybody had this same experience and found thisto be true. What about the temperature showing on the LCD display?

 

On my Protege', I had a similar problem and ended up having to take it to a shop to get the idle speed re-set.

 

I appreciate the info - it turned out that the idle speed problem fixed itself. After the first day, to day and a half, the needle on the odometer stoppedoscillatingerratically. I started thinking about it, and it occurred to me that the idle speedalways returned to the originalspeed. So, I'm thinking the problem was completely related to the ECU(having to reset). Also, the temp guage still works, I just had to press the button labled "AMB"and it reappeared. On the other hand, the LED display doesn't display all the characters (or it displays them half-way), which is slightly irratating, but not detrimental. The car still runs really well.