EPC light on 2004 Jetta. Code said brake switch faulty, but brakes lights worked. Replaced brake switch, now no brake lights.
EPC light comes on intermittently. Had a mechanic look at it and he said code reader said the brake switch was faulty. Brake lights worked, though. I got a new switch at the dealer and followed instructions to replace it. Now I have no brake lights. I checked the fuses and all ok. I checked the terminals on the switch for continuity and it opened and closed when I depressed the brake pedal. I even put the old brake switch back in and still no brake lights. What am I missing?
My car has 45000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
Hi there. The first thing that pops in my mind beyond of what you have listed is perhaps the electrical harness attached to the brake switch. Perhaps the harness itself is damaged or you have an exposed wire, loose ground wire somewhere. You might want to have a professional mobile mechanic come to your location and complete a brake lights not working inspection to help you diagnose this issue.
How to Identify and Fix Common car Problems ?
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Bad Brake Pedal Switch
It signals the brake lights to turn on and also sends a signal to the engine control unit to reduce power, allowing the vehicle to come to a stop. If the brake pedal switch is faulty, it will not send signals to the EPC to reduce the engine power- resulting in an illuminated EPC light.
It sounds like you may have either a blown fuse or a broken wire. Check and replace the fuses/relays as necessary. It may be necessary to check for battery voltage with a digital volt/ohm meter at the brake switch and bulb sockets; be sure to follow the power source power flow chart in the electrical wiring diagram.
When your brake lights are not working but tail lights are, it could indicate a number of issues with your vehicle if the problem isn`t itself with the individual bulb. This could be a smorgasbord of issues from faulty sensors, broken switches to chapped wires, and even electrical problems of the ground.
Malfunctions with fuel metering, timing, or emissions systems. Engine speed sensor failure. Problems with other sensors such as the crank or cam position sensor, mass airflow sensor, and even the brake light switch. Traction control problems.
There are several different causes for an EPC Light to come on. The most common causes are because of a faulty engine sensor, and malfunctions with the air sensor and brake lights. However, there can be many other causes: Wiring issues.
Like all fuses, the brake light system fuse can be found in the power distribution center, which is under the dashboard or tucked away underneath the hood.
The P0504 code is defined as “Brake Switch A/B Correlation” and is a generic diagnostic trouble code (DTC) generated by the engine control module (ECM) of your car. P0504 indicates that the ECM has detected a malfunction in the brake light switch signal circuit (stop lamp or stop light switch circuit).
You can see your brake light switch by looking under the dash, near the top of the brake pedal. The brake light switch is usually attached to a small bracket that holds the switch, activated when the pedal is depressed, in position.
If the lights turn off, the switch is either misaligned or the pedal is in the wrong position. Wire short – You may have a short in the wiring. You can check by unplugging the brake light switch and checking the lights. If they stay on, you have a short circuit somewhere.
If you want to fix the EPC light yourself, you can try the following: first, start the car normally. Then, start the car for the second time and push the gas pedal to the floor when the engine starts. In some cases, this works. It is also a good idea to check the electrical connections on the throttle body.
However, engine oil is crucial to a healthy engine and lubricated parts, so it`s possible an issue that has triggered the EPC light is caused by low oil.
You should never ignore this light when it comes on. It is a clear indicator that there is a problem. The brake control unit, the steering control unit, and the engine control unit all control the EPC. For this reason, it may be challenging to diagnose the cause of the light on your dashboard.
While you can continue to drive with the EPC warning light on, you run the risk of doing significant damage to the engine. To help prevent damage, the EPC`s limp-home mode might activate, making the vehicle sluggish as you seek help.
Using a 25amp Fuse in place of a 30amp Circuit Breaker
Historically auto-resetting circuit breakers have been the standard circuit protection for use with electric trailer brake controllers.
The stop lamp fuse is in the left kick panel inside the vehicle. It is a 15amp fuse that powers the stop light switch on the brake pedal. The brake light switch sends power to rear brake lights.
Failing Brake Systems
Another system that experiences failures that causes illuminated CEL is the brake system. Everything from low fluid levels in the lines to unevenly worn brake pads can cause this light to illuminate.
You should never ignore this light when it comes on. It is a clear indicator that there is a problem. The brake control unit, the steering control unit, and the engine control unit all control the EPC. For this reason, it may be challenging to diagnose the cause of the light on your dashboard.
You should never ignore this light when it comes on. It is a clear indicator that there is a problem. The brake control unit, the steering control unit, and the engine control unit all control the EPC. For this reason, it may be challenging to diagnose the cause of the light on your dashboard.
However, engine oil is crucial to a healthy engine and lubricated parts, so it`s possible an issue that has triggered the EPC light is caused by low oil.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
EPC light on 2004 Jetta. Code said brake switch faulty, but brakes lights worked. Replaced brake switch, now no brake lights.
ANSWER : Hi there. The first thing that pops in my mind beyond of what you have listed is perhaps the electrical harness attached to the brake switch. Perhaps the harness itself is damaged or you have an exposed wire, loose ground wire somewhere. You might want to have a professional mobile mechanic come to your location and complete a brake lights not working inspection to help you diagnose this issue.
Brake lights are not working. replaced brake light swtch still no brake lights. the third brake light the connection was melted at
ANSWER : The first thing to do is to repair third brake light and replace the brake light fuse and then see if the third brake lights work and the lower lights start working? If only the 3rd brake light starts working then you may need a further checks on the turn signal flasher or switch could be bad.
I replaced the brake light switch. Gear lever unlocked because it had locked. Now the brakes feel hard.
ANSWER : Hi, thanks for writing in. You need to check the brake switch install adjustment. You may have the switch adjusted too tight and it is holding the the brake pedal partly down. This will cause the brake master cylinder to not release the brakes when you let off the pedal. Readjust the switch away from the pedal until you feel some free play again in the pedal. This should fix the problem. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.
Okay so when I turn my lights on at night my brake lights do not work, when I don’t have my lights on they work fine.
ANSWER : Hi there. Based on your inquiry, it’s highly probable that you have a damaged light switch or some electrical fault inside the turn signal relay. However, it’s also possible that the brake switch above the brake pedal could also be the source of your problem. Due to the fact that multiple electrical components might be causing this issue, it’s a smart idea to first have a professional mobile mechanic complete a brake lights are not working inspection, so they can determine what’s causing all of these issues and recommend the right repairs.
Abs light, emergency brake light, steering wheel assist light, engine light, EPC light, traction control light
ANSWER : Hello, thank you for writing in. The vehicle does utilize a lot of the same sensors for these systems. Are there any other codes that are coming up when this code appears? If so you will want to take these into consideration when processing the repair and making a diagnosis. The module may be bad, and replacing it should fix the problem. The lights should turn off once the main computer recognizes the new module and the sensors sync up. If you believe the sensors need to be cleaned you may do so. Do as minimal as possible to make sure you are not damaging the sensor or disrupting the wiring inside. A bad connection would make the lights stay on. With so many lights that are effected by the module being illuminated, the module is likely bad or does not have a connection. Check the connection first and then resort to replacing the unit. For more help with these electrical tests, contact our service department.
All dashboard lights and tail lights do not work after driving through a lot of snow. Headlights work. And brake lights work.
ANSWER : Hello. We’ll be happy to help you. There are a few things that I recommend checking to discover why your lighting system is malfunctioning. The headlight dimmer switch should be checked. Along with the wiring harness above the right front tire behind the fender well cover. Also
the main fuse under the hood should be inspected because other people with your particular vehicle have had similar lighting issues if that fuse goes bad. It will be a great idea to check the rest of the fuses in that area too while checking the main fuse. Once the fuses are checked inside of the main fuse box then I would check the fuses inside of their interior fuse box. The interior fuse box should be located on the driver side of the dashboard near where your legs would be. If you need more assistance with repairing your vehicle please keep in mind that our organization provides Mobile Mechanics who can help you diagnose and repair your vehicle, all at competitive rates.
the main fuse under the hood should be inspected because other people with your particular vehicle have had similar lighting issues if that fuse goes bad. It will be a great idea to check the rest of the fuses in that area too while checking the main fuse. Once the fuses are checked inside of the main fuse box then I would check the fuses inside of their interior fuse box. The interior fuse box should be located on the driver side of the dashboard near where your legs would be. If you need more assistance with repairing your vehicle please keep in mind that our organization provides Mobile Mechanics who can help you diagnose and repair your vehicle, all at competitive rates.
Just replaced head gasket, changed crack sensor new plugs. The check engine light is on, but dim, the only other light that the dash is a normal battery indicator. The fuel pump is not running when switch is turned on, the power windows don’t work, it turns over but not firing. It’s like only one part of the system is working. Also the heater fans work even if the switch is off.
ANSWER : I would first look at the diagnostic trouble codes. Those codes are available because the check engine light is on. If the fuel pump is not running (momentarily) at key on, that fault alone will prevent the car from starting as there will be no fuel pressure. Pump output and pressure can be directly tested and you can also check for electrical power to the pump. To find out why the engine will not run, the recommended diagnostic is a no start diagnostic. If you request that service, the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
When I put my foot on the brake my back left brake light goes off, when I take it off the brake the brake light comes on
ANSWER : I would suggest trying to disconnect and reconnect the wiring to the rear lights. I have seen these older Toyota vehicles rear lighting short out on the lights themselves due to the way the light circuit was made on the lamp housing. Look at the housing circuit on the light to see if one is touching another, and that could tell you why it is malfunctioning. There could also be a problem with the brake light switch. If you are not comfortable dealing with wires, I recommend getting in touch with a certified mechanic who can look at your brake light issue for you to see what’s going on.
