ABS and Parking brake light always on
 

I know others have this problem, but I searched and didnt find much.

Previous owner said the Master cylinder failed and pedal went to the floor. Lights have been on ever since. MC, pads, and leaking wheel cylinder were replaced. Brakes feel fine to me, parking brake works well.

What can I check to make the lights go out? I dont have a repair manual yet so I might need a little "extra" help. Thanks.

first thing do you have brake lights ? if the fuse blows the anti lock light stays on.

Yes! brake lights are working.

Unplug the cable to the ABS module for 5 seconds then reconnect it. The module is behind the glove box which you can tip out further by pressing on the plastic in the back.

If there is nothing wrong with the system now the light should stay off. If it comes on again then report back here and we'll get you the error codes and tell you how to get them out of your box.

Edwin

Do a search for RWAL
There's a bunch of stuff on here


Den

If there is a low vacuum signal to your low vacuum warning switch (or a bad switch) it will cause both lights to light up. The switch is located on the inner driver’s side fender and can be found by tracing the small vac line that runs to the brake booster, I think.

I think the Brake light lights up anytime the ABS light lights up. It's a failsafe in case one of the bulbs goes bad.

Edwin

I disconected the ABS control box and removed the ABS fuse from the panel under the steering column.

Both lights are still on.

I grounded the the plug and got 7 flashes.
On another post It says code 7 is:
"BCM fuse pellet blown, isolation output missing, or valve wiring shorted to ground"

What do I do now?

Thanks guys, your help has been great.

I would think BCM fuse pellet would mean the fuse for the Brake Control Module

The isolation and dump valves are combined in the RWAL hydraulic valve which is mounted on the frame rail back near the rear axle. Check the connection there and also follow the wires back forward and make sure nothing is wore through or rubbing the frame or something.

Den

No visible wiring problems. I disconnected and reconnected the plug at the RWAL valve. Connections were clean and tight.

I opened up the BCM to see if there was a fuse inside. There is what looks like a thermal fuse soldered to the board. I wonder if that is the "pellet fuse", it certainly looks more like a pellet than the blade type fuse.

Any other ideas? I would love to solve this.

Did you take an ohms meter to the fuse? If it's what I think it is, it's a surface mount type fuse with a ceramic body that you can't tell if it's blown without an ohms meter.

I have to go check out my own RWAL problems so I'll have more experience in a few days.

Edwin

I tested it for continuity, and it think it was 1.7 ohms across the outer terminals. The inner terminals have no resistance.

That seems a bit high for a fuse. What's the amp rating if you can read it? I would think it should be less than an ohm unless it's a 1/10 amp or smaller.

Not sure what you mean by inner terminals, a fuse should only have 2 terminals. Can you post a digital close up pic of it. I can probably tell you what's what with the fuses. I'm an electronics tech.

Edwin

Here is a pic of the "fuse". Sorry its out of focus, my camera cant focus up close.

I know, a fuse should have only two terminals, What I called the "inner terminals" are the two silver bands running across the body. They are metal and soldered to the PCB. There was no resistance between the two.

On the two ends of the fuse, I measured 12.5k ohms with my DMM set to the 20k scale.

I could find no markings on the piece, even with a magnifying glass. I looks like a thermofuse to me, but who knows. Any idea what this is?

Pellet fuse??

I'm not so sure that's a fuse at all. It might be a reed relay and the reading you got was the coil and the other terminals are the contacts which are open. Your different readings also point to it maybe being a non-linear device such as a diode. I have to pull mine out in the next few days so I'll look at it and see if it's similar and we can compare notes. You can PM me at edwin@freeholdconsulting.com

Edwin