C0590

Code

Generic C — Chassis

Brake Booster Motor A Phase U-V-W Current High

Brand: Generic

Type: C — Chassis

Views: UK: 16 EN: 24 RU: 20

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Page language: EN

Mechanical seizure or binding of the brake booster/pump (jammed rotor, debris, collapsed vanes)
Shorted or partially shorted motor winding(s)
Intermittent short or low-resistance connection in U/V/W phase wiring or connector
Faulty motor driver (ABS/Brake ECU or dedicated driver module) causing excessive output current
Poor or corroded connector/ground causing abnormal current flow
Foreign object restricting motor or pump movement

ABS/brake warning lamp or combination warning illuminated
Reduced or intermittent brake assist; harder pedal or increased pedal travel
Unusual noise from booster/pump (grinding, scraping, or unusually loud motor noise)
Burning electrical smell or smoke in severe cases
Stored DTC(s) related to booster/pump overcurrent or motor faults

Read and record all stored DTCs and freeze frame data with a scan tool
Inspect battery condition and charging system; verify stable 12V supply under load
Visually inspect motor/pump connectors, wiring harness, and grounds for damage, corrosion, or pin pushed out
Attempt to operate the booster/pump while monitoring for noise, binding or abnormal behavior (use scan tool commands if available)
Measure motor phase-to-phase and phase-to-ground resistances with power removed
Measure motor current draw during operation with a clamp meter for each phase to identify imbalance or overcurrent

Supply voltage: nominal vehicle battery voltage (~12 V) stable under load (should not collapse)
Phase currents: all U/V/W phase currents should be balanced and within the manufacturer’s specified operating/current limits (no single phase significantly higher than the others)
Phase-to-phase and phase-to-ground resistances: should be consistent across phases and show no short to ground (manufacturer values vary; expect low ohms but not near zero)
Control signals: PWM drive signals from ABS/booster controller should be present and similar across phases when commanded (use oscilloscope or diagnostic tool)

Retrieve and record DTCs and freeze frame data. Note conditions when fault occurred (speed, load, ambient temperature).
Perform visual inspection of battery, charging system, ABS/booster connectors, harness, and grounds. Repair obvious damage.
With ignition off, disconnect motor connector and measure phase-to-phase and phase-to-ground resistances. Compare phases for imbalance or shorts to ground.
Check supply voltage at motor connector while cranking/commanding pump; verify stable voltage. Low supply can cause driver stress.
Reconnect and, using a clamp ammeter, measure phase currents while commanding the pump through the scan tool (if available) or during the condition. Identify any phase drawing significantly higher current or total current above spec.
If possible, operate the motor while listening for abnormal noises and attempt to turn the shaft by hand (motor removed) to check for mechanical binding or bearing failure.
Wiggle-test wiring and connectors while monitoring current and fault status to find intermittent opens/shorts.
If motor windings, currents, or mechanical seizure are confirmed, remove motor/pump assembly for bench testing or replacement. If motor bench test is good, suspect driver/ECU failure.
Inspect and clean connectors and grounds, repair wiring as required. Replace motor/pump assembly or control module as indicated by test results.
After repairs, clear codes and perform functional tests and road/operational test to confirm fault does not return.

⚠️ Status

Overcurrent detected on Brake Booster Motor A (U-V-W phases). Motor/pump circuit fault — reduced brake assist possible. Service required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours

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