What Does the P0504 Code Mean?
The DTC P0504 is defined as the “Brake Switch A/B Correlation Code.” This reveals a malfunction in the vehicle’s brake switch light. The DTC P0504 is a powerful generic code, and it is applicable to every OBD2 system car as the error code has a close relationship with the Brake Switch system of the vehicle. Moreover, it has a strong correlation with brake diagram junctures. When Error Code P0504 is identified by the scanning tool, it suggests that the vehicle’s internal computer system has identified a sudden shock in the brake light circuit. The PCM then monitors the relative circuits and also scarves for the data devaluation. A lack of voltage can add fuel to the incident.
The brake light switch is deeply connected to the right-hand circuits. The brake switch always emanates two signal output deliverables. The Error Code will register in the memory of the PCM, and that is the thing that you need to solve as early as possible. The PCM fetches the data to the dashboard, and then the CEL is activated. The shift interlock and cruise control system are also harmonious conclusions that have a close connection with the Brake system Switch.
Causes (Quick)
- Faulty brake switch.
- Damaged wiring or connectors in the brake light circuit.
- Blown fuse affecting the brake light system.
- Misalignment of the brake switch.
Solutions (Quick)
- Replace the defective brake switch.
- Repair or replace damaged wiring or connectors.
- Replace the blown fuse.
- Adjust the brake switch to ensure proper alignment.
What Cause of Code P0504?
You may have found a lot of infamous understandings and close calls in the system. Every error code has some backside reasons. DTC P0504 is not a different part of that understanding. Let us see the possible causes of the error code P0504,
- The most contemporary cause of the error code P0504 is that it has a faulty brake light switch.
- A short, defective, corroded, and burnt wiring and connectors could be one of the main causes of the error code P0504. Some subjects play an important role in disseminating the writings. A disconnected profusion of organograms is life-threatening for the vehicle.
- A blown fuse always threatens the car’s braking system, and this could be the main cause of the error code P0504. The fusible links also play a dire role in justifying the code.
- The brake light bulbs could be fused, and if this happens, then the brake can not measure the potential distance of pressing the brake signal. It is not only the light, but if the bulb holders are dismantled, then it can also yield the error code.
- A failing PCM always produces error codes no matter which code it is. The wiring harness may have a Short brake switch.
What Are the Symptoms of Code P0504?
The Symptoms of DTC P0504 are very crucial for measuring and repairing the code. These Symptoms are nothing but indicators of something wrong in the vehicle.
The Check Engine light turns on if the DTC P0504 is on the verge of self-revelation. The Shift interlock malfunction system could be propagating faulty data through to the main PCM, devaluing all the procedures. Vehicle stalls at a maximum cruising speed if the brake pedal is operated in a reversed procedure. The brake light activates itself as the brake pedal is in a miserable condition. Hard shifting to the outlying parking position can be a common symptom for the DTC P0504. The vehicle starts stalling when you press the brake pedal. The gear selector may be stuck out of the insisting position. These are some of the best and possible Symptoms of DTC P0504.
How to Diagnose DTC P0504?
The diagnosis process of the error code P0504 is more or less very much tiresome. So if you do not follow the steps of diagnosis, then it can be difficult to diagnose the code. Let us have a close look into the complete diagnosis process of the DTC P0504,
Stage-1: Diagnose the circuits, connectors, or wires. These parts are the heart of the vehicle. Check the corroded and worn-out wirings. Check the freeze frame data to inspect the Brake Switch A/B Correlation insides.
Stage-2: Diagnose the wiring harnesses with the help of related tools. Inspect the brake light bulbs if they are in the right possession. Check the fuses if they are working or not. Inspect all the cable codes and relate those data with the DTC.
Stage-3: Since there is no fixed cause, the troubleshooting needs a hard set of measures. The PCM software needs a formal cessation so that all the inside processes are going in full swing. The Brake Switch maintains a well-judged mechanism, so inspect and repair with full care.
DTC P0504: Complete repairing process
The repairing process starts with analyzing the freeze frame data. Check the manufacturer-specific manual to note down the structure of the brake light switch. It would be ethical if you repaired the accessible undervalued terminals as soon as possible. Check the input wire and specified voltage with the help of an ohmmeter. Compare these values with the standard values. That will make it easy to make further decisions. Inspect and repair the blown a fuse. 
The brake light bulbs sometimes face consequences that might be too contagious for the braking system. So repair this as early as possible. The battery voltage sometimes fluctuates, which needs an ohmmeter to check the setups. Along with the brake light bulbs, the brake light circuit also feels pain and gets whacked by the recession. The switch is a defective power output terminal or circuit and must be replaced with an OEM replacement to ensure proper operation.
The wiring harnesses could be out of the equation. It needs a vigilant process to outsmart the ongoing statute. The associated circuit systems also need a replacement if the circuit is short. The Controller Area Network bus system needs a cool inspection as it could be the possible illusion of having a bad sensor. So repair the CAN as soon as possible. You need advanced diagnostic equipment to set up all the disputes among the internal mechanisms of the braking system.
Avoid Common Mistakes
The stop light switch consists of a vigorous duplex system that always transmits two separate signals. Those signals have effective consequences on the powertrain control module. The ECM surmounts these two signals to monitor that the brake system is on the right track. If the signals face downfall for some reason, then force the brake pedal to be in the right place.
The detection conditions always work under some certified conditions. If these prerequisites are not maintained, then the diagnosis process will fail miserably. Here I will sum up those favorable detection conditions.
- First of all, the ignition switch must be on to start the diagnosis. Turn off the fuses also.
- The condition of the Brake pedal must be in a position that can release the extra friction that needs to stop the vehicle.
- The STP signal should be in an “off” position. Also, inactivate the ST1 signal to get the maximum favorable outcomes.
- Detach the IGN fuse and Stop the light switch. Finally, Provide amiable space for the PCM.
How much does it cost to fix the P0504 code?
The total cost includes the labor cost and the defective part replacement cost. The labor charge for repairing this error can range between $100 and $150. However, the repair and replacement cost varies with the defective parts’ cost. For example, the brake light switch can be replaced by ranging between $75 to $150. The cost fluctuates based on the car model of the vehicle as well.
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Meet our professional car mechanic, Russell D. Steele, who has been in this field for five consecutive years and works with several automotive companies. He completed the "AUTOMOTIVE & LIGHT DUTY DIESEL TECHNOLOGY" course from NorthWest Lowa Community College, where he learned essential diagnostic and transportation management skills and became a certified mechanic.
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