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Jim
Grant has been working in the automotive industry for over twenty
years. In addition, Jim is an ASE Master Technician with advanced
L/1 certification. He works as manager and technician in his
family's automotive business in New Hampshire. He writes weekly
automotive consumer columns and is editor of an automotive newsletter
that is circulated throughout North America. |
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Jim Grant's Tech Tips
'93 Buick LeSabre, Computer Lock-out
Q:
I bought my father
a ‘93 Buick LeSabre with 97k for $2000 from a co-worker. It worked
beautifully until one morning it wouldn't start. Our mechanic can start
the car from under the hood so he doesn't think it is the starter. When
he turns the key the security light flashes. He thinks the car has locked
itself down and will not respond to either of our keys. It has been in
the shop for 4 days and we are no closer to getting the problem solved.
A:
If you take a look
at the ignition key to the vehicle you will see a small black chip with
a small piece of metal on each side. This chip has an electrical value
that is used by the vehicle’s security system to allow the vehicle
to be started. There are 2 common problems with the system used in your
father’s vehicle. The chip in the key goes bad so no signal is sent
to the security system or the tumbler and housing that the key goes into
is worn and will not allow the signal/code from the chip to get sent to
the security system. The fix? Replace one or the other or both. But there
is a catch. The security system has to receive the right signal/code and
not just any signal/code. It has to be the right one for your vehicle
or it will never start. How do you prove this is the problem? Take an
ohm meter to the metal on each side of the chip on the key and record
the readings/values. Then under the dash of the vehicle there will be
a small 2 wire connectors that come from the key and tumbler housing.
Unplug this connector and check the values and compare it to the reading
recorded from the key chip. This has to be performed with the key installed.
Then turn the key in the housing and monitor the values. If there is a
sudden change just for a moment the key housing/tumbler is bad and has
to be replaced. Why? Because the security system thinks someone is messing
with the vehicle and will not allow it to start. If the key chip is bad
you’ll have to have the vehicle towed to your nearest GM dealer.
They have this tool/computer that goes in place of the key and ids the
security system code. This will allow them to make up a new key to replace
the one with the failed chip. The local hardware store just can’t
help with this one.
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