ACC Low Pressure (X21A9) [11/2021 - ]: Description

Code	Tester Display	Measurement Item	Trouble Area	Output ECU
X21A9	ACC Low Pressure	History of a continuous and significant decrease in accumulator pressure	Accumulator pressure dropped due to frequent brake pedal operation Pump motor malfunction Accumulator deterioration Accumulator pressure sensor (brake booster with master cylinder assembly) Supply voltage reduced	No. 1 skid control ECU (brake booster with master cylinder assembly)