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Home / DTC / C0020 — ABS Pump Motor Control

C0020 — ABS Pump Motor Control

Detailed page for trouble code C0020.

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Code

C0020

Generic C — Chassis

ABS Pump Motor Control

Brand: Generic
Type: C — Chassis
Views: UK: 36 EN: 69 RU: 68
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Page language: EN

Causes

  • Blown fuse or failed relay for ABS pump motor
  • Open, short or high-resistance wiring in pump motor power or ground circuit
  • Corroded, loose or damaged connector at the pump motor or ABS module
  • Failed ABS pump motor (electrical or mechanically seized)
  • Faulty ABS control module (driver transistor or electronics)
  • Low battery voltage or poor main battery/charging system condition

Symptoms

  • ABS warning lamp illuminated (often combined with traction control/ESC lamp)
  • ABS pump does not run when commanded or during self-test
  • Longer stopping distances under ABS activation or reduced ABS function
  • Grating or no audible pump noise when ABS is commanded
  • Intermittent or permanent loss of ABS/traction control functionality
  • Possible change in brake pedal feel when ABS engages

What to check

  • Read and record stored and pending codes with a capable scan tool; note freeze frame data
  • Check vehicle battery voltage (key on engine off and while cranking) and charging system condition
  • Inspect fuses and relays for the ABS pump circuit and replace if blown or failed
  • Visually inspect pump motor connector and wiring for corrosion, damage, chafing or loose terminals
  • Back-probe pump motor connector and measure supply voltage and ground while commanding pump ON with a scan tool
  • Measure pump motor resistance (motor coil) with battery disconnected and compare to expected range

Signal parameters

  • Expected supply voltage to pump: ~11–14.5 V with engine running (varies by vehicle)
  • Control signal type: typically switched DC or PWM from ABS module; voltage range 0–battery volts (0–12 V)
  • Typical pump motor coil resistance (generic range): low, often ~0.1–5 Ω (varies by design) — consult vehicle-specific data
  • Typical running current: can be several amps up to 10–30 A peak during operation depending on pump size; stall current higher
  • When module switches low-side transistor ON, control side should pull near 0 V; OFF should be near battery voltage

Diagnostic algorithm

  1. Safety & prep: Park on level surface, chock wheels, disable vehicle per manufacturer procedures. Have a capable ABS scan tool and appropriate PPE.
  2. Read codes: Record C0020 and any concurrent codes (wheel speed, sensor, communication). Clear codes and attempt replicate to see if code returns.
  3. Electrical baseline: Check battery voltage and main grounds. Poor battery can cause control faults.
  4. Fuses/relays: Inspect and test ABS pump fuse and relay; replace known-faulty items and retest.
  5. Visual/wiring inspection: Inspect harness from ABS module to pump for damage, corrosion, rodent damage or pin corrosion; repair as needed.
  6. Command test: Using scan tool, command ABS pump ON while back-probing the pump connector. Verify battery supply present and module ground/drive switching.

Likely causes

  • Blown fuse or failed pump relay
  • Open/short or poor ground in pump power circuit
  • Failed or seized pump motor
  • Corroded connector at pump or module

Fault status

⚠️ Status
ABS warning lamp (and possibly traction/ESC lamp) illuminated. Fault may be stored or active; pump may not operate when commanded. Driving with ABS disabled increases risk during emergency braking.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

C0021 C0035 C0040 C0110 P0620
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