Chart A2 - Main Valve

WARNING: This page is about a different car, the 1988 Buick Riviera and 1988 Buick Reatta. However, it is still accessible from the selected car via links, so may be relevant.

Main valve is a solenoid valve, located inside hydraulic unit. Valve is activated by EBCM (pin No. 18) to provide modulated boost pressure to front hydraulic wheel brake circuits. Valve is grounded internally to hydraulic unit. Normal resistance is 2-5 ohms.

Fig 1: Main Relay Grounding Schematic

Fig 2: Flow Chart A2, Code 21 - Main Valve

Fig 3: Flow Chart A2, Code 21 - Main Valve (1 of 2)

Fig 4: Flow Chart A2, Code 21 - Main Valve (2 of 2)