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Home / DTC / C05A7 — ABS Pump Motor Supply Voltage B Circuit Low

C05A7 — ABS Pump Motor Supply Voltage B Circuit Low

Detailed page for trouble code C05A7.

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C05A7

Generic C — Chassis

ABS Pump Motor Supply Voltage B Circuit Low

Brand: Generic
Type: C — Chassis
Views: UK: 14 EN: 24 RU: 18
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Page language: EN

Causes

  • Low battery or poor charging system voltage
  • Blown fuse or faulty relay for ABS pump circuit
  • Corroded, loose or damaged connector at the ABS pump or control module
  • High-resistance or short-to-ground in supply wiring (Circuit B)
  • Faulty ABS pump motor (high internal resistance or partial failure)
  • Faulty ABS control module / driver circuit

Symptoms

  • ABS warning lamp illuminated (may also show traction control or ESC lamp)
  • ABS pump may not run or runs intermittently when ABS expected to activate
  • Reduced or inhibited ABS/ESC function under heavy braking or slippery conditions
  • Possible unusual noise or no noise from pump when system commands activation
  • Brake pedal feel may be firmer or different during ABS events

What to check

  • Read DTCs and freeze frame data with a capable scan tool; note conditions (ignition state, vehicle speed, battery voltage).
  • Check battery voltage with key off, key on, and engine running; confirm charging system output.
  • Inspect fuses and relays for the ABS pump supply (Circuit B); replace if blown or suspect.
  • Visually inspect connectors and harness to ABS pump and ABS control module for corrosion, pin damage, or loose terminals.
  • Measure voltage at ABS pump supply pin (Circuit B) with key ON and while commanding pump via scan tool; check for excessive voltage drop under load.
  • Check continuity and resistance between ABS pump connector and ABS control module power pin and ground points.

Signal parameters

  • Battery voltage (key OFF): ~12.0 V (varies by state of charge)
  • Battery/charging voltage (key ON / engine running): typically 13.5–14.8 V
  • ABS pump supply (Circuit B) expected: near battery voltage when pump is commanded
  • Acceptable voltage drop: small (typically
  • Pump motor current: can be high during activation (varies by vehicle; expect tens of amps on some systems)—check service data before measuring

Diagnostic algorithm

  1. Retrieve all codes and freeze-frame data; note battery voltage and conditions when the code set. Attempt to clear codes and perform a short road or ABS activation drive to recheck.
  2. Verify battery state of charge and charging system. Charge or replace battery and repair charging faults before continuing.
  3. Inspect ABS pump power/ground fuses and relays for Circuit B. Replace suspect components and retest.
  4. Visually inspect wiring and connectors at the ABS pump and ABS control module. Repair corroded pins, bent terminals, or damaged insulation.
  5. With a DVOM, measure voltage at the ABS pump supply pin (Circuit B) with key ON and while commanding the pump with a scan tool. Note voltage with and without load.
  6. Check continuity and resistance between the pump supply pin and the ABS module power output pin; check ground integrity between pump housing/connector and vehicle chassis.
  7. If wiring and supply check good, measure pump motor winding resistance and/or perform a bench test of the pump (if service procedure allows). Compare to spec or reference.
  8. If pump motor draws excessive current or shows internal faults, replace pump assembly. If wiring OK but module driver does not supply voltage, consider ABS control module replacement or repair.
  9. After repairs, clear codes, perform ABS actuator test and road test to confirm ABS pump operation and absence of recurrence.

Likely causes

  • Battery state of charge or alternator not providing adequate voltage
  • Corroded/loose terminals at pump or ground strap causing voltage drop
  • Blown pump fuse or sticking/faulty pump relay on Circuit B
  • Damaged wiring harness insulation, chafing to ground, or connector pin corrosion
  • ABS pump motor beginning to fail and drawing excessive current, causing supply sag
  • ABS control module power driver fault for Circuit B

Fault status

⚠️ Status
ABS Pump Motor Supply Voltage B Circuit Low — the ABS control module detected supply voltage on Circuit B below the acceptable threshold while the pump was commanded. This may disable proper ABS pump operation.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

C05A6 C05A8 C0500 C0035 C1234 U0121
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