Code P0504, brake light issue

VANNERGUY

MEMBER
2009 KIA OPTIMA
6 CYL
2WD
AUTOMATIC
193,000 MILES

I have replaced the brake light switch. My brake lights work but it still sets the code.I have noticed that the 2 tailights in the trunklid are dbl contact but only light as tailights. Can you steer me to the possible issue?

Wednesday, August 25th, 2021 AT 8:22 AM

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

The 3rd high-mount brake light shouldn't light unless the brake is applied. If you are getting it to turn on with the parking lights, chances are there is an issue with one of the connectors shorting. Note: The code indicates an electrical system fault related to the brake lights.

If you look below, I provided the diagnostics for the code you indicated. Take a look through them and let me know if you are comfortable performing them. Also, here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

Keep in mind, this could even be related to the light switch.

Let me know if this helps you or if you have other questions.

Take care,

Joe

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Wednesday, August 25th, 2021 AT 7:26 PM

VANNERGUY

MEMBER
1 POST

Too bad nobody actually reads the complaint or question. These hints/tests are for non working brake lights.

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Friday, August 27th, 2021 AT 9:35 AM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

I did read your complaint. I explained that the code indicates there is a fault in the electrical system regardless if the lights work or not. If there is an abnormal signal from the switch (if it works or not), it will set the code. The above directions are to identify variations in the circuit.

Let me know if you need help.

Joe

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