C05A6

Code

Generic C — Chassis

ABS Pump Motor Supply Voltage B Circuit High

Brand: Generic

Type: C — Chassis

Views: UK: 28 EN: 35 RU: 29

AI status

Completed

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Page language: EN

Causes

Short to battery voltage on the pump motor supply (Circuit B)
Failed pump motor driver or internal ABS control module fault
Faulty or corroded connector or wiring harness (opens/shorts causing incorrect readings)
Failed pump motor relay or stuck relay contacts
Aftermarket electrical accessory wired into pump supply
Intermittent or poor ground at ABS module or pump

Symptoms

ABS warning lamp illuminated
Traction control/ESC warning and/or disabled
ABS pump may run unexpectedly or not run when commanded
Possible loss of anti-lock braking and stability control
Blown fuse for ABS pump circuit (in some cases)
Erratic ABS behavior or stored multiple ABS-related fault codes

What to check

Read ABS module fault memory and freeze frame data with a capable scan tool
Visually inspect ABS pump, module connectors and wiring for damage, corrosion, pin push-out or aftermarket taps
Check fuses and pump motor relay for correct operation
Measure battery voltage at battery terminals and at the ABS pump supply pin with key ON and engine running
Measure voltage at ABS module pump B supply pin and compare to battery
Inspect chassis and module grounds for tightness and corrosion

Signal parameters

Normal pump supply voltage (key ON, engine OFF): approximately battery voltage (11–15 V)
Normal pump supply voltage (engine running): typically 13–14.8 V (depending on charging system)
High-voltage condition: sustained voltage above ~15–16 V or voltage spikes above system spec
Pump motor coil resistance (typical): low ohm range — varies by vehicle; expect a low resistance path (consult OEM spec)
Relay coil resistance (typical): tens to a few hundred ohms (refer to OEM data for exact values)
Module ground resistance: near 0 ohms to chassis (

Diagnostic algorithm

Connect a scan tool, record freeze frame/live data, and note any other ABS or charging system codes.
Visually inspect harnesses, connectors, and the pump motor for physical damage, corrosion, or aftermarket taps. Repair any obvious issues.
With key ON (engine OFF), measure battery voltage at battery posts and at the ABS pump supply B pin at the module and at the pump connector. Compare readings.
If pump supply shows higher than battery or unexpected constant battery voltage, disconnect the pump connector. Re-measure at the module harness side to determine if the short/load is in the pump or wiring.
Check and operate the pump relay (if applicable). Swap with identical known-good relay if available. Measure relay contacts for unexpected continuity to B+ with relay de-energized.
Inspect and measure module ground(s). Clean and tighten ground connections as needed.
If wiring at pump side is good and the pump is not the source, suspect internal ABS module/pump driver fault. Perform bench tests per OEM if available or consider module replacement/repair.
Check charging system voltage with engine running. If charging is above specification, diagnose alternator/regulator before replacing ABS components.
After repairs, clear codes and perform functional test/road test to verify fault does not return.

Likely causes

Wiring short to constant battery voltage on ABS pump supply B
Corroded/poor connector at ABS pump motor or module causing abnormal voltage reading
Failed internal pump driver transistor in ABS ECU
Stuck or welded pump relay supplying battery voltage continuously
High charging system voltage (>15–16 V) stressing ABS supply circuit

Fault status

⚠️ Status

ABS warning lamp illuminated; ABS/ESC functionality may be limited or disabled. Repair electrical fault in pump supply B circuit to restore normal ABS operation.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 2.5 hours