Does an engine have to be manually reprogrammed after installing a new battery?

Dear Car Talk

Dear Car Talk | May 01, 2000

Dear Tom and Ray:

We have purchased a 1991 Buick Regal that has a dead battery. It had been sitting
for about six months. We jumped it and drove it to an auto shop to have it
checked out. It was otherwise fine. The auto-shop people said they would sell me
a battery for $79.95 and install it for about $30. Then they said it would take
about an hour and a half to reprogram the computer, which would cost another $35.
A friend at work told me that it's not necessary to reprogram the computer, as it
will reprogram itself when you drive the car. Who's right? Should I go to my
auto-parts store and buy a battery, or spend the $150 at the auto shop? --

RAY: Neither. Your friend at work is right. After a battery change, the engine-
management computer will reprogram itself. It's called a "relearning process,"
and it happens automatically after about five minutes of moderate-speed driving.

TOM: The only thing that won't reprogram itself are the radio presets. But this
is your new car, so you're going to reprogram the radio buttons yourself anyway,
right? No great loss there.

RAY: So I don't know what that extra $35 is for. Maybe it's the labor cost for
driving the car to the doughnut shop while the computer reprograms itself. But
that would be $10 worth of labor and $25 worth of doughnuts. So I wouldn't go
back to these guys.

TOM: But I wouldn't just go buy a battery and slap it in there, either. Part of
the labor involved in installing a battery is checking the car's charging system
to make sure it's functioning properly. If the alternator isn't working or if
there's a current drain somewhere, you'll just kill the brand-new battery, too.

RAY: So take it to a different shop and have the charging system checked and the
battery installed there. If you need the name of a good shop, go to the Car Talk
section of and check the "Mechan-X-Files." It's a database of good
mechanics whom our readers and listeners have personally recommended over the
years -- and we don't charge a "reprogramming" fee to use it.

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