2003 mercury sable electrical issue

Asked by Edward Feb 08, 2019 at 09:42 AM about the 2003 Mercury Sable GS Sedan FWD

Question type: Maintenance & Repair

After a very bad jump start where a Toyota Tundra driver
backwards jumped the battery, it caused a lot of smoke
from both batteries.  Now engine of the sable won't say
running.  Takes another proper jump start (at least 15
minutes each time) for the car to crank over.  After stalling
about 5 minutes after restart, there is no crank until jumped
again.  Cycle continues.  

Here is what I've done so far to no avail:

Checked alternator and battery.... both good
Checked draw voltage from battery.... good
Checked alternator power..... good
Checked all fuses..... none blown
Did discover a constant relay clicking on and off under the
dash fuse panel.  No relay codes were found. Clicking relay
does set off the interior dome light each time it clicks.
Fuses are intact.

So I'm at a loss to figure out what this problem could be.  
My suspicion is ECM related to a power short after
crank/start.  But I'm no mechanic.  Any help would be
appreciated!

1 Answer

9,730

Your car has more than one computer, the engine control and the body control modules probably both cooked at the same nano second the cables were reversed, there are pin-out charts available for you to physically test each circuit but it takes even a trained mechanic a long time to do so you have to compare that to the price of a new computer.

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