hi guys, im currently working on my 1990 sierra sapphire 4x4 cosworth, the abs light comes on with the ignition and stays on all the time, i have tested the following...

• all wheels sensors and pick up rings
• all the relays and fuses
• live and earth to the ecu
• all the hydraulic modlator solenoid valves, in cluding bridging the wiring to check the operation
• the pump motor
• the pressure switch
• the brake pedal position switch
• the brake fluid level warning lamp/switch

the only thing i havent done is connected a pressure guage to the accumulator to check the pressure is all correct but as the pump motor stopped pumping as the fluid got down to the max mark i assumed its all ok...!

im clean out of ideas guys, any help would be very greatful... cheers