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99 STS Electrical problems


jlinde

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A friend of mine found a 99 STS last fall and it is having electrical problems.

He got an extra computer and alternator with it without knowing the reason why.

The charging is going up and down between 16.5 and 13.0 and there are some other

warnings on the panel like change pads and service AC etc.

I have all the books for the earlier 93-94 but I know very little about this 99.

Where is the engine computer mounted?

The extra alternator will be tested and put into the car later to exclude the problem

with that or can a faulty pcm be the source?

Are the diagnostic codes possible to display on the panel as in the 93?

And in case can the codes be found (and explained) on the net?

Help would be appreciated. / Jan L

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....Where is the engine computer mounted?
The PCM is located upstream of the intake air filter.
The extra alternator will be tested and put into the car later to exclude the problem

with that or can a faulty pcm be the source?

The PCM could be the problem because the alternator "F" and "L" terminals are connected to the PCM. It's more likely the voltage fluctuation is caused by something other than the PCM.

It would be worth checking the resistance of the thermistor that is molded into the positive battery terminal connector insulation.

Are the diagnostic codes possible to display on the panel as in the 93?
http://www.caddyinfo.com/readingcodes.html

If your friend is computer literate, send him here.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Thank you so much Jim for this excellent info. My friend is not so good in english

writing so I am trying to help him with his STS - both electrical and mechanical.

I recently installed a hopefully nice engine and auto from 93 in my 94 STS after some work with

heads, timeserting and electrical rewiring because of differences between the 93 and 94

connectors. The 99 obviously contains a lot more electronics so I hope the problems can be solved.

/Jan L

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