C05A4

Code

Generic C — Chassis

Wheel Speed Sensors Supply Circuit Low

Brand: Generic

Type: C — Chassis

Views: UK: 17 EN: 63 RU: 22

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Page language: EN

Causes

Blown or open fuse for ABS/traction/wheel-speed sensor supply
Ignition/relay circuit not supplying power to sensor rail
Short to ground on the sensor supply wire
Open or high-resistance connection in supply or ground wiring
Corroded/loose sensor connector or pin(s)
Failed wheel speed sensor (internal short or load)

Symptoms

ABS warning lamp illuminated
Traction/stability control warning or disabled
Intermittent or no ABS operation
Speedometer or cruise control faults (depending on vehicle)
One or more wheel speed sensor DTCs stored
Possible diagnostics show low supply voltage values at sensor circuit

What to check

Scan for all stored DTCs and freeze-frame data; note which wheel(s) affected
Verify battery voltage and charging system (battery > 12.2 V at rest, ~13.5–14.5 V running)
Inspect ABS/traction system fuses and relays (replace if blown)
Visually inspect wiring harnesses, sensor connectors, and ground points for corrosion, damage, or pin push-out
Backprobe the sensor supply pin with ignition ON and measure voltage at each wheel connector
Measure resistance between sensor supply and chassis ground to detect shorts

Signal parameters

Expected sensor supply: many systems use an ignition-switched 12 V rail (nominal ~9–16 V with engine off/on) or a regulated 5 V reference (nominal ~4.5–5.5 V). Check vehicle-specific spec.
Typical passive sensor AC output: amplitude varies with wheel speed; no DC supply required for passive sensors (if passive, a missing supply DTC may indicate module supply/reg reference fault).
Typical active sensor output: signal is a square wave whose amplitude is referenced to the sensor supply; frequency proportional to wheel speed.
Resistance of passive sensors (if applicable): vehicle-specific — compare to service manual; out-of-range may indicate open/shorted sensor.
Continuity: supply circuit should show low resistance from module fuse to sensor connector pin (check for opens/high resistance).

Diagnostic algorithm

Read and record all DTCs and freeze-frame data; clear codes and attempt to reproduce to confirm persistence.
Verify battery voltage and correct charging; low system voltage can cause false low-supply DTCs.
Locate and inspect ABS/traction fuses and relays; replace any blown fuse and test for recurrence.
With ignition ON (engine off), backprobe the supply pin at each wheel speed sensor connector and note measured voltage. If supply is present at module/fuse but low or absent at a wheel, isolate wiring between those points.
If supply is low at all sensor connectors, check fuse/relay, module power/ground, and module internal regulator circuits.
If supply is low at a single wheel, disconnect the sensor and re-measure supply voltage at the disconnected harness — if voltage returns to normal, the sensor may be shorted. If still low, suspect wiring short to ground or poor connection upstream.
Perform continuity and resistance checks from the module supply pin to the sensor connector to find opens/high resistance; check for shorts to ground using an ohmmeter (power off).
Inspect and repair any damaged wiring, corroded connectors, or poor grounds. Replace faulty sensor if confirmed.
If wiring and sensors test good, test or replace the ABS/TCM module (or perform module bench test) per manufacturer procedure.
Clear codes and road-test to confirm repair; verify ABS/traction systems function and no recurrence of C05A4.

Likely causes

Blown fuse or relay for the sensor supply
Open/poor connection at sensor connector or ground
Short to ground on the supply wire near a wheel or harness chafe
Faulty wheel speed sensor
Faulty ABS/TCM module (less common)

Fault status

⚠️ Status

Low voltage detected on the wheel speed sensor supply circuit. Wheel speed sensors may not be receiving proper power; ABS/traction functions can be affected. Inspect supply fuse/relay, wiring, connectors, and sensor/module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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