04 WJ. brake line went out so replaced all lines with new SS lines. Master pump had all kinds of "sludge" in it and decided to replace it at the same time. Bench bleed master cylinder and bled all 4 wheels. ABS light on once finished and restarted the engine. Didn't drive it and pulled the ABS fuse in the power distribution block, turn on engine ABS light was out. Plugged fuse back in and ABS was on but also the red brake light. Drove about a mile and the ABS light went out. The red brake light remains lit. I've disconnected the E brake wire and the fluid level sensor plug with no change, Brakes work great but I can't figure out why the brake light is still lit. Is there another sensor somewhere that I'm missing? Before you say check for codes / errors, been there, done that, no codes or faults on engine or ABS system.

Thanks in advance guys.

 

Disconnect the battery to reset the computer. The light may be off when you restart. The brake light is a default for when the ABS light burns out. Resetting it may help.

 

Dave, I think that you might have solved why my brake light is on, My jeep always had the ABS light on if the light burned out than maybe that is why the Brake Light is on.

 

I have to admit I read that in my FSM.

 

You can disconnect the ABS module to see. That would turn on your ABS light. If it doesn't, then you know the ABS light is probably burnt out and is the reason for the brake light being on.

I did look up some more on your particular case jeep58. I do not have any FSM or anything to really know.. I am not an expert mechanic. The information I gather is from multiple online sources. I put things together with the general knowledge I have on these things.

There is no clear schematic for the brake warning lamp.. It is on multiple pages of FSM's..

The CCD bus is involved as well as the BCM. In fact the BCM has a "red brake warning lamp driver" built into it using the GY/BK wire.

The instrument cluster diagram isn't a whole lot of help since it shows the brake warning lamp, high-beam indicator lamp, check engine lamp, and cruise control lamp connected in unison.

You can check the BK/GY wire from ignition switch to BCM red brake warning lamp driver... to trace down a short there (to the brake warning lamp driver in the BCM). It should be noted: I believe only in Canada do they require headlights to be on full time. This (brake warning lamp driver in the BCM) may actually be linked up with the "Daytime running lamp module" somehow (from what I read) but not sure? Only pointing this out since if you don't have this module, they may still have the connector in place shorting to ground if connected to nothing. You could have some type of short in the ignition switch itself to the BCM leading to the brake warning light driver, the daytime running lights module or a linked connection to it at its ordinary location, or an issue with a BCM module on the fritz.

It seems strange to have the daytime running lights module trigger a brake light, but I have read at least one account of a guy with a 1998 ZJ who was able to trace the brake warning light being on constantly.. directly related to an issue with this module. It was suggested to him by a guy with a Canadian version ZJ. He said he messed with the daytime running lamp module, and by doing this, he was able to make the brake warning light to go on and off. The story was never exactly finished. Except for him to say that he was going to be replacing the entire BCM, related to other issues he was having as well...

 

Dave, I tried the disconnecting the battery. Left it disconnected over night and still have the issue. I know the ABS light works as it comes on with all the other lights when the key is first turned on. I am at a loss.

 

Noah, you are correct, the wiring diagram on these things is a joke to be polite about it. What exactly is the CCD bus?

 

PCI bus CCD bus...? It is a one-wire communications system between all of the vehicle computers - all of the different modules located throughout the vehicle. To be able to link the modules up with, and to allow communication with the PCM. It is the PCI bus system. It basically means, 'computing' system, I think?

 

From what I understand,

The reasons for the red brake warning light being on could be the parking brake switch, the proportioning valve switch, the proportioning valve itself the spool being moved enough to set off the proportioning valve switch because of an imbalance having been detected with pressure differences between the front and rear braking systems (possibly a stuck spool in the proportioning valve related to maybe having done an improper brake fluid bleeding procedure, or having a break in the integrity of one of the braking systems lines causing an imbalance detected by the spool at one point maybe in the past, since the proportioning valve spool is not considered to always self reset once the pressure variance has been restored between the front and rear braking systems), the brake fluid level sensor in the master cylinder, the ABS light being burnt out, a short from the ignition switch wiring leading to the BCMs brake warning light driver,

Or, maybe a fault with the BCM itself, or maybe a problem within the PCI bus system causing a disturbance to the proper functioning of the BCM module, and its brake warning light driver.

I think that is about it?

(edited to add):
There is also the Canadians wiring version to consider. The daytime headlamp module being a possible source to trigger the brake warning light? Also, irregardless of wether or not you even have the daytime headlamp module, it is still possible to have this wiring run to it anyway.. If so, it could be shorted out, even though it is essentially terminally connected to nothing.. This scenario would result in triggering the brake warning light to illuminate.

 

The simplest way to check warning lights for being burnt out is the bulb check when you first turn the key on. If it doesn't light then, it's burnt out.