Outside lights come on by themselves

KTG123

MEMBER
2003 HYUNDAI ELANTRA
AUTOMATIC
109,000 MILES

Exterior lights randomly turning on while car is off, doors are closed and locked, and keys are not in the car let alone the ignition, what can cause? I have had multiple times now where I or a family member or friend have gone outside to find my exterior lights on in my car, all doors are locked, its turned off and the keys are not even in the vehicle. They were off when I got out and locked it up and when in to where ever I was going work/ home etc. We have to turn it on and off and they will turn off. Usually I leave the switch on because they turn off when my car turns off usually but now I'm thinking I am going to have to remember to turn them on and off every time I drive. My battery died recently and now we think it may because this has been happening more than the 3 times I know about. What could be causing this to happen?

1 Reply

HMAC300

MECHANIC
48,601 POSTS

Yep, this is common when the system telematics control unit (TACM) goes out which controls the outside lighting such as the running lights. This unit is located under the dash on the left side, here is how to change it out. Let us know what you find.

Battery voltage is applied at all times to both the coil and contact of the tail lamp relay from Fusible link BATT. With the light switch in PARK or HEAD, the coil of the tail lamp relay is grounded through the ETACM/ TACM.

Battery voltage from fuse 6 and fuse 7 is then applied to the lamps (side marker lamps, tail lamps, park lamps and license lamps) through the closed tail lamp relay contact and all the lamps go on.