P0504 on Kia
Brake Switch "A"/"B" Correlation
P0504 on Kia vehicles indicates brake switch "a"/"b" correlation. Au7o has documented this code across 1 Kia model — most commonly on Optima. Most vehicles use two independent brake switch signals (a normally-open and a normally-closed circuit, switch A and switch B). The PCM compares them and expects them to change state together when the brake pedal is pressed. P0504 sets when the two signals disagree (do not correlate), indicating one switch or circuit is faulty.
Common Causes of P0504
- •Failed brake light switch
- •Misadjusted brake switch (plunger gap)
- •Wiring/connector fault on one of the two brake switch circuits
- •Blown brake-circuit fuse affecting one signal
- •Faulty PCM input
P0504 on Kia by Model
Kia Optima(1 issue)
- Brake Switch Failure Causing Inoperative Brake Lamps and Shift Issues2008-2010
Kia recall SC098 (NHTSA 13V-114) covers 2008-2011 Optima vehicles with a stop-lamp switch that may malfunction. Brake lamps may fail to illuminate, cruise control may not disengage, push-button start or brake-transmission shift interlock operation may be affected, and the ESC warning light may illuminate. This indexed page retains its existing 2008-2010 year scope.
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View P0504 across all makes →Frequently Asked Questions
What does P0504 mean on Kia?▼
P0504 stands for "Brake Switch "A"/"B" Correlation." Most vehicles use two independent brake switch signals (a normally-open and a normally-closed circuit, switch A and switch B). The PCM compares them and expects them to change state together when the brake pedal is pressed. P0504 sets when the two signals disagree (do not correlate), indicating one switch or circuit is faulty. On Kia specifically, this code is documented across 1 model.
What causes P0504 on Kia vehicles?▼
Common causes on Kia: Failed brake light switch, Misadjusted brake switch (plunger gap), Wiring/connector fault on one of the two brake switch circuits, Blown brake-circuit fuse affecting one signal, Faulty PCM input. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0504 on a Kia?▼
Repair costs vary widely depending on the root cause and specific Kia model.
Which Kia models have P0504 documented?▼
Au7o has documented P0504 on 1 Kia model: Optima.