How to Replace a Brake Light Switch on a Chrysler 300 (2005-2009), Dodge Charger (2006-2009), or Magnum (2005-2008)
The other day the cruise control on my car quit working and the check engine light (Malfunction Indicator Light or MIL) came on. When the light first came on, I was puzzled as I was in the middle of driving at about 50 mph down the road. The misfortune of this event has allowed me to make a how-to guide about it.
A scan of the computer revealed the following error code: P0572 - BRAKE SWITCH 1 STUCK ON. The possible causes listed for this code are:
A) Misadjusted brake switch
B) Brake switch open or short circuit
C) Poor brake switch electrical connection,
D) Failed brake switch.
I promptly went to the nearest auto parts store and purchased a new brake switch for about 10 dollars and some change. Now it was time to replace the defective part. The steps to making this repair are detailed below:
Step 1: Inspect the New Part
Inspect the new switch prior to purchasing it to make sure that it is not defective. Check the electrical connectors and plastic tabs  to make sure they aren't broken. Depress the plunger  lightly a few times to ensure that it springs back. And finally check that none of the locator tabs  at the base of the plunger are broken.
Step 2: Gather the Necessary Tools
For this repair, you will need 4 tools. You will need a 1/4inch drive socket wrench , a 1/2inch socket , a long stemmed flat tipped screwdriver , and a flashlight .
Step 3: Disconnect the Battery
Disconnect the battery at the negative terminal  using the 1/2inch socket and 1/4inch drive wrench . It is always advisable to disconnect the battery when performing maintenance or repairs on your vehicle. This will protect you and the car from accidental shocks or short circuits. On this particular car, the battery is located in the truck under the mat and next to the spare tire.
Step 4: Move the Front Seat
Move the front seat  back as far as it will go. You will need to be able to squeeze your body into the tight space under the dash.
Step 5: Locate the Brake Switch
Looking under the dash, you will find a lot of items. The brake light switch is located at point  in the figure. Arrow  shows the brake pedal travel hole and arrow  is the brake pedal itself. To reach the brake light switch, you will need to carefully insert your right hand into the brake pedal travel hole. Place a small flashlight on the upholstery next to the brake pedal to help you see what you are doing.
Step 6: Remove the Brake Switch
The brake light switch can be easily removed from the holding bracket  by depressing the brake pedal with your left hand and twisting the unit  about 30 degrees in the counter-clockwise direction with your right hand. Carefully slide the brake light switch out of the holding bracket. Release the brake pedal when the plunger has cleared the hole in the holding bracket.
Step 7: Disconnect the Wires
You can see now how the brake light switch plunger is disconnected from the holding bracket hole . To remove the wiring , use the long stemmed flat tipped screw driver to depress the green tabs from the electrical connector (not pictured). Once a small gap has developed between the connector and switch, insert the screwdriver into the gap and gently pry it apart. Use caution at this step as you do not want to break any of the plastic on the electrical connector. Also be careful not to tug on the wires too hard or you may damage the connection in up near the top of the dash.
Step 8: Compare the Parts
Before you run in and install the new switch, you should verify that it matches the old one. Check the shape and dimensions of the part and the materials it is made of. Count the number and verify the shape of the electrical contacts as well (don't touch the contacts). Most auto parts stores won't allow you to return a part once you have installed it, even if it is the wrong one. Don't think about trying to fool them either because they will check the part. In this case, the brake light switches are the same (neglect the difference in color of the locator tabs).
Step 9: Install the New Switch
Insert the new brake light switch upward through the brake pedal travel hole. Reconnect the electrical wires making sure that the pins are correctly aligned. Press the connector onto the switch until you hear it click. Once the wiring harness is reconnected, insert the switches plunger into the holding bracket hole (see arrow  on step 7). While depressing the brake pedal with your left hand, use your other hand to push the switch into the bracket toward the front of the car. Twist the switch clockwise about 30 degrees to engage the locator tabs. You should feel it click into place. Slowly release the brake pedal. You may hear a ratcheting sound when you release it. This is the brake switch plunger 'setting itself' within the unit.
Step 10: Finish the Job
You may now reconnect the battery. Start the car as you normally would. Wait a few moments and then pump the brakes. Watch to see if the check engine light comes back on. Give your car a test drive around the block just to be sure. Congratulations, you've just replaced the brake light switch on your Chrysler 300 (2005-2009), Dodge Charger (2006-2009), or Dodge Magnum (2005-2008). Be sure to watch for more how-to guides from me in the future; at least the next time my car needs a repair.
Questions & Answers
Why is it important to disconnect the battery when replacing a brake light?
It's important to disconnect the battery as a precautionary measure whenever working on any part of your car, especially anything electrical. Disconnecting the battery will prevent you from getting shocked or from accidentally shorting out an electrical component. This prevents the chance of injury from an electric shock and reduces the possibility of damaging a vehicle.