On my 93 Sierra, the guy I bought the truck from had been attempting to bleed the brakes, and also put on a new master cylinder. The truck stops, but when I brake hard it feels like the old drum brakes did. Anyones guess as to which direction it will pull. The brake light has been for a week, since i bought it, but now it started flashing: dot dot dash dot dot dash. Two quick blinks, and a short illuminated pause. Owners manual says nothing about this type of warning, other than a constant illumination of the light. Also, I need to mention that this morning i checked the fluid level and its filled completely to the top, to where when you put the lid back on, it overflows. I need to drain some out, correct?

 

Idk about flashing but if you have trouble try flushing brake lines ill look for code online

 

When the key is first turned on the RWAL module turns the dash brake indicator light on for 2 seconds, then it should go off.

The RWAL system can store trouble codes.

The RWAL system is only capable of storing one code at a time.

You can retrieve RWAL codes without a scan tool.

To retrieve RWAL codes connect a jumper wire between terminal H and terminal A of the ALDL connector with the key on (engine not running). Watch the dash brake lamp and count the blinks. Sometimes RWAL system send out a phantom blink before the code blinks start. It can take up to 20 seconds for the code to start coming out.

Checking the code with this method can set a false code 9.

You can clear the code by removing the fuse for 10 seconds then reinstalling it. The fuse should be labeled STOP/HAZARD or BRAKE. Removing the RWAL fuse will not clear the code.

If you get one long flash and 5 shorter flashes that is a code 6.

If the light is blinking the manual states you should still check the codes by turning the key on (engine not running) and put a jumper wire between terminal A and H of the ALDL. Count the brake light flashes.

On trucks built after Aug 1994 a scanner is required to retrieve codes 6,9,10

This site tells how to read your codes. Chevy C1500 Brake Light Is On

This site has general information about RWAL. http://www.babcox.com/editorial/tr/tr89850.htm

Code 4 testing: NOTE: the isolation/Dump Valve is out by the master cylinder. It is an aluminum block with two round thinks and has brake lines going to it. Key OFF, unplug the Isolation/Dump valve, test the resistance between terminal C of the Isolation/Dump valve and the body of the valve. This tests the switch. Also test the resistance between terminal C and terminal D of the Isolation/Dump Valve. Both tests should measure greater then 50,000 ohms. If they measure less than this the Isolation/ Dump valve is bad.

If it tests ok, with the connecter still unplugged, turn the key on, measure the voltage between terminal C and terminal D of the wire harness that connects to the Isolation/Dump valve. It should be 4 volts or more. If it reads 0 volts replace the RWAL ECU (flat black plastic box by the master cylinder). If it tested 4 volts or more, and it sets a code 4 again, after clearing the code, replace the Isolation/Dump valve.93 Sierra brake light flashing

 

When the key is first turned on the RWAL module turns the dash brake indicator light on for 2 seconds, then it should go off.

The RWAL system can store trouble codes.

The RWAL system is only capable of storing one code at a time.

You can retrieve RWAL codes without a scan tool.

To retrieve RWAL codes connect a jumper wire between terminal H and terminal A of the ALDL connector with the key on (engine not running). Watch the dash brake lamp and count the blinks. Sometimes RWAL system send out a phantom blink before the code blinks start. It can take up to 20 seconds for the code to start coming out.

Checking the code with this method can set a false code 9.

You can clear the code by removing the fuse for 10 seconds then reinstalling it. The fuse should be labeled STOP/HAZARD or BRAKE. Removing the RWAL fuse will not clear the code.

If you get one long flash and 5 shorter flashes that is a code 6.

If the light is blinking the manual states you should still check the codes by turning the key on (engine not running) and put a jumper wire between terminal A and H of the ALDL. Count the brake light flashes.

On trucks built after Aug 1994 a scanner is required to retrieve codes 6,9,10

This site tells how to read your codes. Chevy C1500 Brake Light Is On

This site has general information about RWAL. http://www.babcox.com/editorial/tr/tr89850.htm

Code 4 testing: NOTE: the isolation/Dump Valve is out by the master cylinder. It is an aluminum block with two round thinks and has brake lines going to it. Key OFF, unplug the Isolation/Dump valve, test the resistance between terminal C of the Isolation/Dump valve and the body of the valve. This tests the switch. Also test the resistance between terminal C and terminal D of the Isolation/Dump Valve. Both tests should measure greater then 50,000 ohms. If they measure less than this the Isolation/ Dump valve is bad.

If it tests ok, with the connecter still unplugged, turn the key on, measure the voltage between terminal C and terminal D of the wire harness that connects to the Isolation/Dump valve. It should be 4 volts or more. If it reads 0 volts replace the RWAL ECU (flat black plastic box by the master cylinder). If it tested 4 volts or more, and it sets a code 4 again, after clearing the code, replace the Isolation/Dump valve.