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There's a large number of 156 owners out there, including me, with infocentres reporting bonkers figures due to an extra km to miles conversion in the system.

A generally accepted theory I've heard is that after a battery off event, the speedo header permanently switches to a different output unit, but I don't think this is correct.



My infocentre has the problem and also the service counter irrecoverably says "expired". I just set it to show km and accepted that those are actually miles. But on Monday night while traveling from the Lakes to Hampshire I noticed my average speed was 120, I was doing 85, it was showing km/h. I quickly pop into a service station and change the units back to miles and mpg and the thing is making perfect sense for the rest of the journey, even the live mpg was spot on. I was also now able to reset the service counter.

Unfortunately the next morning it was back to its old ways again. Before it had worked I had moved the car, then restarted it 5 mins later. My theory is that the battery has too low a CCA rating. I think that the Power on reset and Brown out reset in the microcontroller in the screen follow different code paths, the latter being to go into a sort of safe mode which skips the logo display, mangles British figures and disables service counters. It's plausible that the oil resting around my engine made the second crank easier and did not trip a BOR in the uC.

Can those with the issue answer these questions:
-Did your issue start with a battery off event, or a battery replacement?
-When the issue is present, is your service counter "expired"?
-If so, can you reset the service counter?
-Can you try the following procedure next time you go somewhere:
1. Start your car from cold.
2. Wait 30s.
3. Stop your car.
4. Wait 5 minutes.
5. Start the car and go where you want to go, does the infocentre now work properly (you may have to let it warm up to see)?

I've got a better battery back in the lakes that I'm going to try when I go back.
 
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