maredi

Had intermittent error for abc. Garage advised that rear battery was problem, was week needed a replacement. I purchased an agm battery thats supposed to hold a charge better and last longer. The problem I have now is the key. If the car sits for 2 days the locks will not work and the key will not turn in ignition. As soon as I connect a charger to the rear battery it will turn and fir up. In my search I found that if the battery reads 12.75v. all is fine. After a few days it drops to 12.3 volts, and then it will not function. The command was replaced last year and the car worked fine. I don't know if the car uses the radio antenna for the remote or not but that would not stop the key from turning in the ignition. The batteries have been changed in both remotes and they act the same. Any help would be greatly appreciated. Thanks in advance.

kbob999

Electrical issues are hard to diagnose over the net. Here's some food for thought.

You may have a battery drain somewhere...like a glove box light or something.
The rear battery will drain slowly, but should last a couple weeks if fresh, not 2 days.
You will need an AGM battery maintainer like Battery Tender or similar. Plug it in if parked for more than 3-4 days.

On the other hand, you may have a charging issue from your alternator. Bad regulator is common, which bolts to the rear of the alternator. I replaced my regulator, then had the alternator fry about 2000 miles later. Lifetime warranty rebuilt alt, and all is well.

Last - you may have a battery control module acting up, or a SAM unit, or bad EIS (electrictronic ignition switch), or many other potential issues.

Let us know what resolves it. We rely on this data to fix our own.

maredi

Thanks for the post and information. The first thing I have decided to do is pick up a new battery from the dealer tomorrow. I am thinking the quality of the battery i purchased is not up for the task. The front battery is old and still reads 12.88volts yet the new rear one was only reading 12.5. I will let you know how it turns out. Thank You

Tommyboy928

rear batteri is just for consumer tings, front batteri is for only start, even if trunk batteri is empty total, put key in ignition,and front batteri should start car. seems you have somthing going on there that drain batteri in trunk alot. the batteri numbers you show, seems fine .

maredi

Wen't to the dealer today, new battery was no use. The figure its a security problem so I'm going to have it towed there on Monday. I got a feeling this is going to really hurt, but it has to be fixed. Thanks all for your inputs, i'll post the outcome when I get it back.

maredi

Was fun getting the car onto flat bed, but it got on unscathed. Dealer checked car and found two faults. The ignition switch and a security fault. They ordered an ignition switch ($1100 installed) then will check to see if the security fault clears with the replacement. Will let all know how it turns out.

maredi

Got the car back yesterday. Took longer due to bad weather in this area. The ignition switch was replaced, the alarm fault needed a new siren, the valve cover gaskets and related hoses all came to $2000. The car works and runs great. Should be a good summer coming up.