1994 Grand Voyager ABS brake issue

Once the light has turned on, there will be at least one diagnostic fault code stored in the ABS Computer. That will lead you to the circuit or system with the problem, not necessarily the specific defective part. The buzzing you're hearing is the computer activating the solenoids to modulate brake fluid pressure to one or more wheels in response to the computer thinking one wheel is slowing down too fast. That can be due to a loss of signal from one wheel speed sensor for a number of reasons. When the yellow warning light turns on is a clue too. If it comes on while driving and not pressing the brake pedal, the computer might be detecting an extra pulse from one front wheel speed sensor per tire revolution due to a cracked tone ring. That's what's happening on my '95 Grand Caravan. It takes from 100 feet to a mile or more before the light turns on, and it will reset off each time the engine is restarted. If your light turns on before the van is moving, there is more likely a problem in the hydraulic controller or pump. The system is deactivated when the light is on.

I also have a '93 Dynasty with the Bendix-10 system. That one gets its power assist from the pressurized brake fluid that is held in storage. If you have that system, a pump problem will have an affect on your power assist. There was a recall on that system to replace the piston assembly in the master cylinder. My '95 ABS system is different. That uses a standard vacuum power assist booster so it will still have normal power assist if the ABS system shuts down. I'm not sure which system was used in '94.

Start by finding a mechanic with a scanner that can access the ABS computer to read the fault code(s).

Caradiodoc

I found my '94 service manual. It would appear you have the Bendix-4 ABS system. That uses a standard master cylinder and vacuum power booster.

I really get the impression there is internal leakage taking place in the master cylinder based on the pedal dropping but it would seem the red warning light would be on too for unequal pressures in the two hydraulic circuits. It is also possible for there to be a leak in modulator but I don't have any experience working on them. I DO know you don't want to let the system run out of fluid while replacing other brake parts such as calipers and wheel cylinders. The base brake system can be pedal-bled with a helper, but you must have the Chrysler DRB2 or DRB3 scanner to activate some valves to bleed the modulator.

There are no fault code descriptions shown in the service manual but they do make reference to latching and non-latching codes. Latching codes deactivate the system even if the problem is intermittent and goes away. You must turn the ignition switch off and restart the engine to reset the system. With non-latching codes, if the problem goes away, the light will turn off and the system will be functional again without having to cycle the ignition switch off and back on. Either way, the fault codes will remain in the computer's memory. Having those codes read will point you toward the cause of the problem. If an intermittent problem doesn't show up for a long time, the codes will erase automatically after 50 engine starts so it's important to have them read before that happens and that valuable information is lost.

Caradiodoc