Chrysler Repair: ELECTRICAL PROBLEM, attacted, chrysler 300

Question
I have a 1999 Chrysler 300 and it began starting ittermittently a few weeks ago. I had it taken in to a shop and the car started continuously for the mechanic.  The check engine light had come on and had been read but did not have any fault codes stored.  The mechanic by process of elimination seemed to narrow it down to an ignition module and replaced that.  The car computer was also reset in the midst of all this.  Mechanic told me car was fixed so I went to pick it up.  The mechanic also had a key made for the car. I went to pick up the car and the car started and drove but I noticed that the car's check engine light was on and the alarm system light was on so I took the car back to the mechanic. He pulled the fault codes and said he was now sseing codes that he had not seen on the car before after diagnosing some other issues he now says the computer is bad and needed to be replaced. He also mentioned that the car's computer has burnt out the ground on the car now. Does this sound feasible?  I have removed my car from his possession becaus this has taken 2 weeks and now my car is completely dead.

Answer
Hi Constance,
You are correct to have removed the car from this mechanic. If the car is completely dead then that has to be resolved first. Do you mean there are no interior lights when you open the door? If so, then either the battery is disconnected/poorly connected or is discharged. So I would start by check the connections to the battery. Begin at the - post and see if the clamp is tigtly attacted to the post. Then very carefully check the + post clamp to see that it too is not loose on the post. Do this by grasping the insulated cable at the clamp and do not put a wrench on the bolt of the + clamp. Rather if you find it to be loose, then loosen and remove the - clamp and then it will be safe to tighten the + clamp bolt. Then re-attach the - clamp and tighten its bolt. You could otherwise have the wrench short circuit the battery and produce a burn to you hand.
If the clamps are tight and still things are 'dead' then the battery needs to be charged and we need to find out why that happened. It would be helpful to have a volt-ohm meter to do that trouble-shooting. A simple digital meter for around $20 would do the job.
Let me know specifically where things stand after you check out the battery and we'll go from there.
The battery is located on the right side of the engine compartment, under the air cleaner housing. The -post wire is connected to the a large 'tower' in the right side rear corner of the engine compartment, just above the air inlet tube from the air cleaner housing that goes to the engine. So start by disconnecting that wire at the tower. Then remove the air cleaner housing, Then the battery splash shield. You should then be able to see/reach the battery posts/clamps.
However, if the battery does show some life, i.e. the interior light are working, let me know as we may be able to charge the battery without going to it.
By the way, if the battery isn't comletely discharged, you can pull the fault codes using your ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer reading and see the mileage reading will disappear and be replaced by 4-digit numbers. Tell me what those numbers are.
Roland