The code 12 is for low voltage. I would have the battery checked and the charging system checked.
Below is the description and a flow chart.
DIAGNOSTIC TROUBLE CODE 12
Low Battery Voltage
The diagnostic monitor measures the voltage at Pin 13 of the diagnostic monitor connector. Voltage at Pin 13 should be equal to battery voltage. If the voltage measured at Pin 13 drops to less than 9 volts, the diagnostic monitor will flash out Diagnostic Trouble Code 12.
Low battery voltage at diagnostic monitor Pin 13 can be caused by:
1. An open in Circuit 937 (R/W) that would prevent battery voltage from reaching diagnostic monitor Pin 13.
2. A short to ground in Circuit 611 (W/O) or 612 (P/O) may result in a blown instrument panel fuse 5.
NOTE: If the instrument panel fuse 5 is blown be sure to diagnose the system for Possible Causes 2 and 3.
3. An internal short to ground within the safing sensor may result in a blown instrument panel fuses.
4. A concern in the charging system causing battery voltage to drop below 9 volts.
Tuesday, January 1st, 2019 AT 4:16 PM