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Can you explain better what it is doing?
The power brakes are not working (have to press really hard on the breaks for the vehicle to stop), and the ‘brakes’ & ‘ABS’ lights came on the dash. This has happened before (about a year ago), while driving, suddenly the indicator lights turned off and the power brakes worked again. But, about 2 minutes later the ‘brakes’ & ‘ABS’ lights came on and the power brakes stopped working again. The day after this, somehow everything was working again.
It sounds like your hydraulic power unit has failed, The previous incident may have been a intermittant failure. Your truck uses hydraulic pressure instead of vacuum. Here is a description of it.
DESCRIPTION AND OPERATION The hydraulic power unit comprises an electrically driven pump and a pressure switch. The pressure switch incorporates three electro-mechanical switches: one for the pump, another, at a different pressure setting, to illuminate the pressure warning light. The latter switch plus the third switch inform the ECU of low pressure and that ABS function should cease whilst pressure remains low. The pump also incorporates a non-return valve, a low pressure inlet filter, and a pressure relief valve to protect the system.