ABS brake problem, 1994 Chevrolet Corsica

If the vehicle does not have ABS brakes, The wheels will lock on a hard/panic stop. This is why ABS was developed so the operator can maintain some control during hard/panic stops

ABS sensor has nothing to do with the restriction of the brake oil supply. It merely tells the ECU whether the wheel is spinning or stopped at all when the car is moving.
Check:
- Pull up the ABS diagnostic error codes.
- Brake hose attached to the caliper for swollen or clogged.
- Check brake pipe from the skid control ECU to front wheel.
- Check the caliper assembly.

Popular problems with the Lumina and the corsica,let me describe you problem just when you start out after it sat for awhile you step on the brake a the rear brakes suddenly grab and what happens the whole rear end dips. the drive a little more and it brakes normal.,Why the ABS light uneven brake condition or road condition or even tire condition set this off. The type of brake shoe brand has alot to due with this to and there a porpotioning valve for this. dealer sell these its worth it or just get used to back bottom out and be gentle as you brake the car.There not a real cure.

Look at the front brakes. If they did their job, the rear brakes possibly wouldn't need to lock up. Also check the emergency brake that it's adjusted properly; if its cam (at rear brakes) is rotated because of maladjustment of the cable, that might cause a wedged effect when the brakes are applied.

ANTI-LOCK BRAKE SYSTEM (and HCU-Hydraulic Control Unit)
General Information The 4-Wheel Anti-lock Brake System (ABS) is an electronically operated, all wheel brake control system. Major components include the power brake booster, master cylinder, the wheel speed sensors, and the Hydraulic Control Unit (HCU) which contains the control module, a relay, and the pressure control valves. The system is designed to ****** wheel lockup during periods of high wheel slip when braking. Retarding wheel lockup is accomplished by modulating fluid pressure to the wheel brake units. When the control module detects a variation in voltage across the wheel speed sensors, the ABS is activated. The control module opens and closes various valves located inside the HCU. These valves, called dump and isolation valves, modulate the hydraulic pressure to the wheels by applying and venting the pressure to the brake fluid circuits. Some models are equipped with a Traction Assist (TA) system. The TA system senses wheel spin upon acceleration, turns on the Hydraulic Control Unit (HCU) pump and applies fluid pressure to the appropriate rear wheel. Two additional isolation valves in the HCU will also close to permit fluid to flow only to the rear wheels. The TA system monitors TA usage to avoid overheating the rear brakes. If the system does sense brake overheating, the ABS module will inhibit TA operation until the rear brakes are permitted to cool down.
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SYSTEM COMPONENTS The anti-lock brake system consists of the following components:

• Vacuum booster and master cylinder assembly
• Hydraulic Control Unit (HCU)
• ABS module
• Wheel sensors
• Pedal travel switch

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On 1992-1994 and 1995-00 a scanner is used to perform the brake bleed. But on yours, I think it's different according to the manual.
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What do you mean change the cal. on the rear also? Do you mean Caliper?

check too see if the emergency cable is froze

The most common bleeding procedure is to bleed the ABS brake furthest from the master cylinder first, then bleed the other brake that shares the same hydraulic circuit (which may be the other rear brake on a rear-wheel drive car, or the opposite front brake on a front-wheel drive car or minivan). After these have been bled, you then bleed the other brake circuit starting with the furthest brake from the master cylinder.
Air can be very difficult to remove from an ABS modulator assembly because of all the nooks and crannies inside the unit. The modulator may have eight to 10, or more, ABS/traction control solenoid valves, plus various check valves and dead-end ports. Some ABS modulators have special bleed screws to help you vent the trapped air when bleeding the system. Others do not and require the use of a scan tool to cycle the ABS solenoids while you bleed the system. 1. To bleed the isolation valves in the modulator, there are two bleeder screws. Start with the one toward the engine. Turn the ignition on and apply light pressure on the brake pedal. Open the bleeder screw and allow the fluid to flow until clear. Close the screw and do the same at the second bleeder screw. 2. Depressurize the accumulator by pumping the pedal 40 times with the key off. Wait about two minutes for the brake fluid to de-aerate, then refill the fluid reservoir with DOT 3 brake fluid. 3. Now you can bleed the boost section. This is done by applying moderate pressure on the brake pedal and turning the ignition on for three seconds, then off. Repeat this a total of 10 times. Make sure the pedal feels firm when you have finished, and give the car a road test to make sure the brakes are working properly.

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

Itcould be that the brakes installed on your car were not the Original Manufaturers (OEM) recommended pads and/or shoes on the back and front. Or only two of the brakes were replaced. when installing breaks install the OEM's or original breaks for your Corsica.
If a given set of replacement linings are more aggressive than the original, the brakes may feel grabby or upset front-to-rear brake balance increasing the risk of the front or rear brakes locking up on wet or slick roads especially if the more aggressive linings end up on the back brakes. On the other hand, if the replacement linings are less aggressive than the original linings or have less fade resistance, the vehicle may require increased pedal effort and take longer to stop than before. And if these linings end up on the front brakes, they may increase the risk of rear wheel lockup, too.

Most of the time with the rear brakes locking up the brake drums are warpped. If you remove the rear brake drums and take them to almost any auto parts store (Napa, Checkers ect.) they will turn the drums for about $10 a piece.

After you have the drums turned you will need to readjust the rear brakes.