What are the common causes of C0594?

A failed brake booster motor A. Open or short in the brake booster motor A circuit. A corroded connector at the brake booster motor A. A weak ground or low voltage at brake booster motor A.

Read all codes and confirm the brake booster motor A fault. Check battery voltage and grounds at the brake booster motor A. Test the brake booster motor A circuit for opens and shorts. Command the brake booster motor A and watch the response. Replace the brake booster motor A if it does not respond to command. Clear the code and retest.

C0594

Brake Booster Motor A Performance

System: Chassis control (C code)
Lamp: Check Engine Light
Category: Chassis

What it means

C0594 means Brake Booster Motor A Performance.

Check these first

A failed brake booster motor A
Open or short in the brake booster motor A circuit
A corroded connector at the brake booster motor A
A weak ground or low voltage at brake booster motor A

What to do next

Read all codes and confirm the brake booster motor A fault
Check battery voltage and grounds at the brake booster motor A
Test the brake booster motor A circuit for opens and shorts
Command the brake booster motor A and watch the response
Replace the brake booster motor A if it does not respond to command
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.