t99rick

I own a 98 a4 1.8t quattro. Lately I've been sinking some money into her to fix some overdue repairs. One of them being the ABS module. The abs light, and brake light have been on for roughly a year now (abs light is solid, brake light blinking.. and also the three really annoying beeps everytime you turn the car on). My first step into solving this problem was to run Vag-com and see if I could communicate with the abs module. No communication at all. I couldn't even access any other modules without removing the ABS module fuse. After coming to the conclusion that the ABS module is most likely faulty, I matched the part number and ordered a remanufactured module from autoecu.com.

Just a couple hours ago I installed the remanufactured abs module and ran Vag-scan. I was able to communicate with the controller immediately. Scanned for faulty codes... Nothing. No codes at all. But.. My abs light, and brake light were still there. Pretty disappointing. I tried disconnecting the battery for 30 minutes hoping to reset the ecu and clear the lights, didn't work. I also tested the wheel speed sensors because I've heard those can cause the abs, and brake lights. The wheel sensors were all dead on according to vag-scan, all registered the same speed while driving down the road.

So, I'm stumped. If anyone has any advice, or can think of anything I'm missing it would be greatly appreciated.

awcjacobs

When you depress the brake pedal, do your brake lights come on? Might be a brake light switch. On my A6, both ABS and Ebrake light came on and would make warning noise. Thought it was ABS, but was brake light switch.

t99rick

Thank you for the suggestion. I am still getting brake lights. I just ran another vag scan and under the auto trans scan I picked up fault code (00526 - brake light switch-f, 27-00 - implausible signal). Soooo I'm guessing that you were right. I'm going to see if I can find a brake light switch tomorrow morning. Why do you think that the fault code came up under the 'auto trans' module on VCDS lite? I will keep you posted with what happens. I can't wait to get rid of the lights on the dash, and the horrible beeps everytime I start the damn car!

By the way, I noticed your car details, I used to have an 02 a6 2.7t, gray, tip. Loved it, very fast. Sold her last fall

t99rick

Well, I haven't tried to replace the brake light switch yet, but I'm losing hope that that is the problem. I scanned the auto trans with vag com and got the 00526 brake light switch f, implausible signal.. Ross-tech states on their website: "Many Automatic Transmission Control Modules will show a DTC 00526 or 17087 that indicates a faulty brake light switch. This can be ignored and will not appear if you press the brakes once before checking for Fault Codes." My question is.. Will the 00526 brake light switch f fault code cause my abs light, and brake light to appear on my dash? Or is it something else?

I'm going to try to take the brake light switch out and replace it. I also need to register VCDS lite so I can perform a throttle body adaptation, and possible figure out these abs lights a little easier.

Any suggestions would be great. Thanks in advance!

awcjacobs

I am not certain why a brake light switch error would come from the trans module, but best guess is because that module measures how hard the engine is working to shift. Braking is part of engine deceleration.

Yes, faulty brake switch will cause ebrake light and ABS because it is part of the braking system. Plus the design is to make the driver 'scared', rightly so because a faulty switch would mean you have no brake lights, which would require urgent repair due to the safety.

But I think replacing the switch is worth a try. A new switch from the dealer should not be a lot of money. Unbelievable yes, but the switch for my A6 was a little under $6 + tax, that from an Audi dealer. Usually I walk in and expect to pay $500.00 minimum every time. So assuming that they are the same price for an A4, I think it is worth a try.

awcjacobs

Another idea it might come from the Auto Trans would be to make the car go into 'limp mode' With my faulty switch, the car went into limp mode.

t99rick

Update: Just installed a new brake light switch this morning. No luck. Still have the abs light, and brake light on the dash. Brake lights work fine. I was able to clear the brake light switch fault code and it didn't come back immediately like it was. As it stands I am not picking up any fault codes under any of the modules. And like I said before, my wheel speed sensors seem to be working fine. My front rotors are in really rough shape. I've been meaning to replace them... Does anyone think that that could cause the abs light, and brake light? I'm just out of ideas. Thanks in advance for any advice.

awcjacobs

Damn

I hate to think of this now and even say it, but your brake fluid is topped right up?

t99rick

Yeah, I have triple checked the brake fluid. It's just below the max fill line. The tech guy from the company that I bought the abs module said to just drive the car and go through 50 key cycles (starting the car) and the car will reset itself. I have a hard time thinking that is going to work. I'm going to run another vag scan in the morning cuz it's been a few days and see if I pickup any codes. Is there a relay in the dash associated with the braking system? The abs fuse in the fuse panel is good. Thanks again for the ideas. This one is about to make me take the car to a mechanic! I never ever do that! Lol

awcjacobs

Hey Man, with some time, did your brake light and ABS light go out?