Changing your Digital Speed Display Units in an Aston Martin DB9

Digital Speed Display in KM/H

My DB9 was repainted recently, and was in the shop for 7 weeks.  While it was there I don’t think they had it on a battery tender and the battery was low or went flat.  When that happens, your car looses many of the memory settings in the door modules, seat modules, etc.  When I got my car back though and was finally driving it home I looked down at my digital speed display and it said I was doing 120! [I would never do such a thing :>)]  Yet I was rolling along at the same speed of normal California freeway traffic.  Being a Canadian [hiding in California], I knew what was up – my speed was displaying in Km/hr rather than MPH.  I guess when the battery was low, the car forgot which units to display the speed in.  But, how to get it back to normal?

Procedure

This is one of those things I figured they’d actually built into the car to be owner adjustable.   If I take a drive from California to Canada (which I did this summer!), when I get to Canada it might be nice to flip the display over into Metric for my time there.

The first place I checked had the answer.  I pulled the Owners Manual out of the glove box and looked up the Instrument Cluster in section 4.   In the section on the Trip Computer (page 4.17 in my manual) was their description and method to toggle back and forth between Km/hr and MPH (check out the full manual page here).

This will take you 30 seconds.  It can even be done while driving, but I suggest you do it while stopped for safety.

  • Have the car on.  Doesn’t need to be started, but the key needs to be all the way on.
  • Make sure your digital display is reading the current road speed (0 MPH or 0 Km/hr) so you can tell it’s fixed.
    • If it’s not, press the button on the end of the turn signal lever stalk a few times to cycle through all the various information you can display on the digital display until you get to the speed display.
  • Simultaneously Press and hold these two buttons for 5 seconds until the units change
    • The ‘Read’ button on the center console (shown as ‘C’ in their diagram above)
    • The end button on the signal lever stalk once (the ‘D’ button on their diagram above)
    • You should see the speed unit toggle from MPH to Km/hr or back.
  • Release both buttons

That’s it.  Easy.

Digital Speed Display in MPH

What’s interesting to note is their small comment about “The display will always return to the default display units when the ignition is switched off”.  This made me think that when I turned the car off it was going to default back to Km/hr.  Is there some default Metric or Imperial setting for the car?  Is my car stuck in Metric now and I will need to take it to the dealer to reprogram?  I’d already turned my car on and off several times coming home from the paint shop, and it was staying in Km/hr each time.   Their note appears to be wrong.   When I toggled back to MPH, it has stayed in MPH after many restarts.   Toggle it back to Km/hr and it stays in Km/hr.  Not sure what the manual was suggesting, but I prefer it working just as it does.

Another quick note:  The climate control temperature display unit doesn’t change with this.  My speed was in Km/hr and my temperature was in °F.  I guess the temperature control is toggled some other way (not that I needed to fix it).  If you know how, please leave a comment below.


Video

I made a short video showing you how to change this here.  Check it out.

[Coming Soon]

4 thoughts on “Changing your Digital Speed Display Units in an Aston Martin DB9

  1. Scott

    [From 6SpeedOnline] If you want to convert the temp to F, key in turned off, hold down radio presets 4+5 together, still holding presets turn on the key to position II..temp should change from C to F or vise versa if F to C with in 5 seconds

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      1. Scott

        Hi Steve. Tried it this morning on my 2006 DB9 and it works. The “alternate” scale appears very quickly. In my case (normally Celsius) Fahrenheit appeared within a second of turning the key. Within another second or two it switched back to Celcius while I was still holding the 4+5 keys. You have to release the 4+5 keys quickly to make the change, while the alternate scale is showing.

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      2. Hi Scott. Awesome that it works on your car. I’m frustrated all the goodies like this don’t seem to be part of the programming on the 2005. I can’t get the wiper change position trick to work either. Same idea, but with 8 + 9 keys I’ve heard.

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