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Home / DTC / C1D21 — Wheel module

C1D21 — Wheel module

Detailed page for trouble code C1D21.

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C1D21

LAND ROVER C — Chassis

Wheel module

Brand: LAND ROVER
Type: C — Chassis
Views: UK: 3 EN: 6 RU: 3
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Page language: EN

Causes

  • Wheel module internal fault or failed electronics
  • Open/short in power or ground circuit to the wheel module
  • Corroded, loose or damaged module connector or wiring
  • Faulty wheel speed sensor or sensor wiring at the wheel module
  • CAN/LIN bus communication fault or interference
  • Low battery voltage or intermittent supply

Symptoms

  • ABS, DSC or traction control warning lamp illuminated
  • Reduced or disabled ABS/ESC functionality (loss of braking interventions)
  • One wheel speed reading missing, intermittent or implausible in scan tool live data
  • Vehicle speed or stability systems behaving inconsistently
  • Multiple related fault codes stored (ABS, BCM, other wheel module codes)

What to check

  • Read all stored codes and freeze-frame data from ABS, engine and body modules
  • Check live data: wheel speed values for each wheel and status of wheel module
  • Inspect wheel module connector and wiring for corrosion, damage and secure fit
  • Check vehicle battery voltage and charging system (key on and engine running)
  • Measure power and ground at the wheel module connector with harness connected
  • Measure CAN (and LIN if present) bus voltages at the module connector (idle voltages and continuity)

Signal parameters

  • Wheel speed sensor waveform (AC voltage or frequency) and sensor resistance (ohms)
  • Wheel module supply voltage (approx. 11–14 V key on/engine running)
  • Module ground continuity to chassis and battery negative
  • CAN High and CAN Low voltages (approx. 2.5 V idle; differential ~0 V idle, ~ +/-2.5 V active)
  • CAN bus continuity and termination resistance (approx. 60 ohms total)
  • Module wake/sleep or LIN signal (if applicable) and module present flag/status in live data

Diagnostic algorithm

  1. Record full fault list from scan tool (ABS, BCM, engine). Note freeze-frame and whether code is current or historic.
  2. Clear codes and attempt to reproduce. Monitor live data for the affected wheel speed and module status while driving or on a lift (use safe procedures).
  3. Visually inspect the wheel module and connector for corrosion, water entry, damaged pins or loose fasteners. Repair or replace damaged connectors/wiring.
  4. Check battery voltage and charging system. Low supply can cause module faults — recharge or replace battery if necessary.
  5. With connector connected, measure supply voltage and ground at the module pins (key on). Compare to vehicle reference. Repair any supply/ground issues.
  6. Measure wheel speed sensor resistance and signal while rotating the wheel (use oscilloscope or frequency meter). Replace sensor if out of specification or intermittent.
  7. Check CAN bus voltages at the module connector and verify continuity to ABS/BCM. Inspect termination resistors and other nodes for faults.
  8. Perform wiggle and backprobe tests while monitoring live data to find intermittent wiring faults caused by suspension movement.
  9. If wiring and sensors are good and communication is lost or module reports internal faults, consider replacing the wheel module. Follow manufacturer procedures for module coding/programming and security pairing.
  10. After repair or replacement, clear codes and perform road test to confirm fault does not return. Re-scan all related modules for stored errors.

Likely causes

  • Corrosion or water ingress at the wheel module connector
  • Broken/shorted wiring harness to the wheel module from suspension movement
  • Faulty wheel speed sensor mounted in the hub
  • Internal failure of the wheel module electronics
  • Loss of CAN bus communication due to faulty termination or other node

Fault status

⚠️ Status
Wheel module fault — communication, sensor or electrical fault detected at wheel module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

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