GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Component Replacement

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SYSTEM FILLING



The master cylinder is filled in the usual manner with no special procedures being necessary. Only DOT 3 brake fluid must be used; silicone or DOT 5 fluid is specifically prohibited. Do not use any fluid which contains a petroleum base; these fluids will cause swelling and distortion of the rubber parts within the system. Do not use old or contaminated brake fluid.

RWAL ECU/EBCM



See Figure 1

The Electronic Brake Control Module (EBCM), formerly known as the RWAL Electronic Control Unit (ECU), is a non-serviceable unit. It must be replaced when diagnosis indicates it is faulty. Because it is expensive and normally non-returnable, be absolutely sure the module is at fault before replacement.

  1. Turn the ignition switch OFF . The switch MUST be OFF whenever you are connecting/disconnecting power from the module. Failure to do this may destroy the computer.
  2.  
  3. Disengage the wiring harness connector(s) from the computer control module.
  4.  
  5. Grasp the module and remove it by pulling toward the front of the vehicle. If necessary, gently pry the tab at the rear of the module while pulling.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: RWAL ECU/EBCM mounting

Do not touch the electrical connectors or pins; do not allow them to contact brake fluid. If contaminated with brake fluid, clean them with water followed by isopropyl alcohol.

To install:
  1. Install the computer module by aligning it and carefully sliding it into the bracket until the tab locks into the hole.
  2.  
  3. Engage the wiring harness connector(s) to the module.
  4.  
  5. Turn the ignition ON , then verify proper system operation.
  6.  

ANTI-LOCK PRESSURE CONTROL VALVE



The Anti-Lock Pressure Valve (APV), formerly known as the isolation/dump or control valve assembly is not serviceable. The entire component must be replaced as an assembly should a malfunction be confirmed.

  1. Turn the ignition switch OFF . The switch MUST be OFF whenever you are connecting/disconnecting power from the module (as will done later in this procedure). Failure to do this may destroy the computer.
  2.  
  3. Disconnect the brake line fittings at the valve, then immediately cap or plug all openings to prevent system contamination or excessive fluid loss. Remember to protect the surrounding paintwork from damage by fluid spillage.
  4.  
  5. Disengage the bottom connector from the RWAL ECU/EBCM. At NO time should you allow the APV to hang by the wiring.
  6.  

Do not touch the electrical connectors or pins; do not allow them to contact brake fluid. If contaminated with brake fluid, clean them with water followed by isopropyl alcohol.

  1. Remove the bolts holding the valve to the bracket.
  2.  
  3. Remove the valve from the vehicle.