What are probable causes for an ABS warning light to come on even though brakes feel normal?

Looks like you have a few issues there.

1. The battery warning. This is indicative of a weak battery and if your battery is 3 years old or more I would replace it.

2. If you have a weak battery this can trigger other warning lights in the vehicle, typically the ABS warning but sometimes other warning lights as well depending on the electronic features in the car. If you replace the battery this should correct the battery warning and most likely the ABS warning if both of these warnings appeared at the same time.
Normally, once the ABS warning is displayed the anti lock braking system(ABS) will be shut down. Whilst your braking will be normal, if you brake too hard and lock up your wheels on a slippery road there is no ABS assist to prevent the brake lock up which you have when the system is working.

3. If the alternator on the engine is not generating sufficient power and thus not charging the battery at all, or very little, you will likely get a battery warning light. I don't know if your 1999 vehicle has a warning light to indicate a faulty alternator or not.

4. Check Engine Light.
You suggested the CE warning has been showing up for a few days and before the battery and ABS warnings popped up.
The CE warning can be caused by dozens of different engine issues.
The vehicle needs to be scanned with the appropriate scan tool to see what fault codes the onboard computer is generating because if you have a CE warning light there will be fault codes generated 99% of the time.

Once these fault codes have been pulled the mechanic can start to diagnose the cause of the problem or problems. Each engine fault code your car's computer is generating can be caused by different types of problems so it is important that they diagnose the issues correctly. Otherwise your Check Engine light will remain on as long as the causes are not identified and fixed.

"Is it possible if I bleed all four brakes they might shut off?"

If you bleed the brakes all you will do is remove any air in the brake lines and replace the brake fluid with new fluid. Do this in any event if the brake fluid is 2 yrs old or more.

This will have no affect on the ABS warning light and when the light is displayed the ABS has turned off because there is a problem with the ABS. You will not get it back on until the cause is determined and fixed which may be just a failed wheel speed sensor.

The brake warning has probably been triggered by the same failure that has caused the ABS warning light (since they came on together and bleeding the brakes should make no difference).

If the car sat for 2 months, no doubt the battery went flat. You have not mentioned anything about the battery but if your battery is in poor shape this can trigger warning lights in many cars especially the ABS (and stability control systems).

The best option is to have the vehicle scanned for fault codes that have been generated and there will be one or 2 if these warning lights are displayed. Scanning the ABS for codes will show up one or more issues and you can trace the problem from there. I think you will find the brake warning and ABS warning have been caused by the same fault.

In any event make sure you check the brake fluid level in the car and look for any external leaks of fluid that may have developed. Check the operation of your brakes to ensure they are working normally and that the brake pedal is not slowly dropping to the floor when you continue to apply pressure. Bleed the brakes if the brake fluid is 2 yrs old or more.

When I had that problem with the emergency light it was the sensor for emergency brake
The abs and brakes sounds like you are loosing pressure in the system

Because there is a fault in the system and the electronically operated anti-lock braking system has been de-activated.
You will still have normal braking though. However, If you lock up the wheels under heavy braking there is no system in operation now that releases the brake pressure to permit the wheel or wheels to rotate and gain traction. It is all manual control, ie. you have to control any lock up you cause yourself with the braking pressure you apply.

The most likely cause of the ABS warning is a failed wheel speed sensor or sensors. The warning will remain until the cause is identified and fixed.

Possibly a defective ABS sensor, or low brake fluid. Recommend a reputable mechanic to assess the issue.

Anything that disables the ABS,pull the fuse,disconnect a wheel sensor,unplug the controller,
will turn on the ABS light and the brakes will be normal base brakes.

There are a few sensors and components which feed into a computer.Even though your brakes seem fine,there is something wrong.ABS takes sensor inputs from the wheel speed,sends them to a computer,compares them to how hard you want to brake,and applies/releases the brakes as fast as possible to prevent skidding.You normally cannot feel it.So even though you can stop,something is giving a bad signal somewhere.The computer is usually not the problem though.The sensors and brakes are under the more extreme usage conditions.Greg

the wheel baering is going bad leting the axle kick sideways causeing light

Anti-Lock Control —Vehicles Built After 03/2002 The 3-channel anti-lock brake system consists of the following components:

• front wheel speed sensors
• front wheel speed sensor rings
• hydraulic control unit (HCU)
• Anti-lock brake control module (ECU)
• rear wheel speed sensor
• rear wheel speed sensor rings
• yellow anti-lock brake warning indicator

The 4-channel anti-lock brake system with traction control and stability assist system consists of the following components:

• active brake booster with integral solenoid
• brake booster release switch
• front wheel speed sensors
• front wheel speed sensor rings
• hydraulic control unit (HCU)
• stability assist module (ECU)
• stability assist event indicator
• lateral accelerometer
• longitudinal accelerometer (4x4)
• rear wheel speed sensors
• rear wheel speed sensor rings
• steering wheel position sensor
• yaw rate sensor
• yellow anti-lock brake warning indicator
• brake pressure transducer
• traction control switch

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I suspect the abs issue is causing the speed control not to work if it happened at the same time the cruise control stopped working. When the yellow ABS light comes on, it means the ABS is dactivated. You may have a faulty accelerometer which senses acceleration and yaw (side to side lean). I have not seen a bad one but you said it is sensitive to acceleration.
I would unplug it and see what happens. The connector should have a small tab to depress so you can pull the connector out.
Here is where it is:

Accelerometer Removal and Installation

1. NOTE: The accelerometer is located under the center, rear passenger seat carpet. (I think you have to remove seat for access).
   Cut the carpeting along the perforations.

1. Disconnect the electrical connector.

1. Remove the nuts and remove the accelerometer.

Have dealer hook up tester and pull fault codes if you can't find an easy solution.
Some background info

A malfunction in the anti-lock brake system will cause the anti-lock brake control module to shut off or inhibit the system. However, normal power-assisted braking remains.

Malfunctions are indicated by the yellow ABS warning indicator in the instrument cluster.

The anti-lock brake system is self-monitoring. When the ignition switch is turned to the RUN position, the anti-lock brake control module will carry out a preliminary self-check on the anti-lock electrical system indicated by a three-second illumination of the yellow ABS warning indicator in the instrument cluster.

During vehicle operation, including normal and anti-lock braking, the anti-lock brake control module monitors all electrical anti-lock functions and some hydraulic operations.

Each time the vehicle is driven, as soon as vehicle speed reaches approximately 20 km/h (12mph), the anti-lock brake control module turns on the pump motor for approximately one-half second. At this time, a mechanical noise may be heard. This is a normal function of the self-check by the anti-lock brake control module.

Pedal pulsation coupled with noise while braking on loose gravel, bumps, wet or snowy roads is normal and indicates correct functioning of the anti-lock brake system.

Warning Lamp Indicator
The anti-lock brake system (ABS) uses the yellow ABS warning indicator to alert the driver of a malfunctions in the ABS.
The yellow ABS warning indicator will come on to warn the driver that the ABS has been turned off due to a symptom that exists in the ABS. Normal power assist braking remains but wheels can lock during a panic stop while the yellow ABS warning indicator is illuminated.

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Please report back, I am curious if that is what it is. Good luck

Sounds like you have a bad sensor. No you can not hurt anything by driving with the light on, but you do want to try to keep your warning lights clear