Component Tests and General Diagnostics

Fig. 111 Modulator Operational Test. Starion:

1. Connect pressure gauges with a range of 0 to 2100 psi, one to rear brake exit point and other between master cylinder and modulator, Fig. 111.
2. With engine idling, hold brake pedal at a point which results in reading of about 711 psi on pressure gauge B.
3. While watching pressure gauge B, operate the release solenoid valve. System is normal if pressure suddenly drops to about 0 psi.
4. If pressure does not drop to about 0 psi, maintain pressure as described in step 2 and operate the build up solenoid valve then stop operation of release solenoid valve while watching pressure gauge.
5. If pressure suddenly rises to about 711 psi the system is normal.
6. Repeat step 3 and then, with the build up solenoid valve in the non-operating position, increase fluid pressure on master cylinder and check rear brake fluid pressure.
7. If pressure gauge B does not show a reading of 1422 psi when brake pedal is depressed until gauge A shows a reading of 1707 psi, replace the modulator.