GM Full Size Vans 1987-1997 Repair Guide

Isolation/Dump Valve

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TESTING



  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the isolation/dump valve harness from the ECU.
  4.  
  5. Check the dump valve coil resistance between terminals B and D. If the resistance is greater than 3.0 ohms, replace the assembly. The resistance should be between 1.0 and 3.0 ohms.
  6.  
  7. Check the isolation valve coil resistance between terminals A and D. The resistance should be between 3.0 and 6.0 ohms. Replace the assembly if the resistance is above 6.0 ohms.
  8.  
  9. Check the resistance of the anti-lock valve switch between terminals C and D and then check it between C and the assembly body. If the resistance is less than 50,000 ohms in either test, replace the assembly.
  10.  

REMOVAL & INSTALLATION



The isolation/dump valve is not serviceable. Replace the unit only when defective.

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the brake line fittings using a flare nut wrench.
  4.  
  5. Disconnect the bottom electrical connector from the ECU. Do not allow the isolation/dump valve to hang by the pigtail.
  6.  
  7. Remove the valve from the vehicle.
  8.  

To install:
  1. Install the valve and torque the bolts to 21 ft. lbs. (29 Nm).
  2.  
  3. Connect the electrical connectors and reconnect the brake lines using a flare nut wrench. Torque the fittings to 18 ft. lbs. (24 Nm).
  4.  
  5. Connect the negative battery cable and bleed the system.
  6.  

 
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