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Home / DTC / C1020 — Right Rear Wheel Speed Sensor Circuit Malfunction

C1020 — Right Rear Wheel Speed Sensor Circuit Malfunction

Detailed page for trouble code C1020.

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C1020

Generic C — Chassis

Right Rear Wheel Speed Sensor Circuit Malfunction

Brand: Generic
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Damaged or chafed wiring harness to right rear wheel speed sensor
  • Corroded/loose connector or poor ground
  • Failed wheel speed sensor (magnetic or Hall type)
  • Damaged or missing tone/ring reluctor on wheel/hub
  • Wheel bearing damage causing sensor misalignment
  • Contaminated sensor (metal debris, heavy rust)

Symptoms

  • ABS warning lamp illuminated
  • Traction control and/or stability control warning lights illuminated
  • Possible loss of ABS/traction control functionality
  • Erratic or zero wheel speed reading for right rear on scan tool
  • Pulsating brake feel or altered ABS operation during braking events
  • Occasional false slip/stability interventions

What to check

  • Read all stored and pending ABS/traction codes and freeze frame data with a scan tool
  • Observe live wheel speed sensor data for all four wheels at low rolling speed
  • Visually inspect right rear sensor, connector, wiring and tone ring for damage, corrosion or debris
  • Check for play in wheel bearing and correct sensor air gap to reluctor/tone ring
  • Wiggle harness and connector while watching live data to find intermittent faults
  • Measure sensor resistance (for passive sensors) and supply/pull-up voltages (for active/Hall sensors) at the connector

Signal parameters

  • Passive (magnetic) sensor: DC resistance often ~800–3,000 Ω (varies by vehicle). Produces AC voltage that increases with wheel speed (typical low-speed AC ~0.2–2.0 VAC).
  • Active (Hall/active) sensor: requires reference supply (commonly 5V or 12V) and provides a digital square or pulse output (0–5V or 0–12V) at a frequency proportional to wheel speed.
  • Typical pulse frequency: low speeds tens of Hz, rising with wheel RPM; exact values are vehicle-specific — compare to other wheel sensors.
  • Expected behavior: stable, symmetrical waveform without dropouts or high noise; no open circuit (OL) on resistance check for passive sensors.

Diagnostic algorithm

  1. Connect a scan tool and record C1020 and any related codes; note freeze frame and live wheel speed values.
  2. Verify vehicle-specific sensor type (passive vs active) from service data before electrical tests.
  3. Perform a visual inspection of the right rear sensor, tone ring/reluctor and harness — repair obvious damage or contamination.
  4. With wheel supported and rotated, observe live sensor data. If the right rear shows zero or erratic pulses while others are normal, suspect sensor/hardware or wiring.
  5. For passive sensors: disconnect sensor and measure DC resistance at the sensor leads; compare to spec or the opposite wheel. Check for open/short to ground.
  6. For active sensors: verify reference voltage/pull-up at the sensor connector with key on; then backprobe signal while rotating wheel — expect digital pulses.
  7. Use an oscilloscope to verify waveform integrity (amplitude, symmetry, no dropouts).
  8. Perform a wiggle/rock test on harness and connector while observing live data to find intermittent faults.
  9. Inspect and measure continuity and resistance of wiring back to ABS module; check grounds and connector pins for corrosion or bent pins.
  10. If wiring and sensor test good, swap right rear sensor with an identical known-good sensor (or swap with left rear if same type) and see if fault follows the sensor.
  11. Repair or replace failed sensor, damaged wiring, corroded connector, or damaged tone ring as indicated. Repair grounds and module connectors if faulty.
  12. Clear codes and perform a test drive to confirm repair; re-scan to ensure C1020 does not return.

Likely causes

  • Wiring harness damage or connector corrosion at right rear sensor
  • Failed right rear wheel speed sensor
  • Damaged or missing tone ring on right rear hub
  • Ground or power feed problem to sensor

Fault status

⚠️ Status
Right Rear Wheel Speed Sensor Circuit Malfunction detected. ABS/traction control may be disabled; the fault indicates an open/short/intermittent or invalid signal from the right rear wheel speed sensor circuit.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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Code

C1020

MERCEDES-BENZ C — Chassis

CAN Communication Fault

Brand: MERCEDES-BENZ
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Damaged or chafed wiring harness to right rear wheel speed sensor
  • Corroded/loose connector or poor ground
  • Failed wheel speed sensor (magnetic or Hall type)
  • Damaged or missing tone/ring reluctor on wheel/hub
  • Wheel bearing damage causing sensor misalignment
  • Contaminated sensor (metal debris, heavy rust)

Symptoms

  • ABS warning lamp illuminated
  • Traction control and/or stability control warning lights illuminated
  • Possible loss of ABS/traction control functionality
  • Erratic or zero wheel speed reading for right rear on scan tool
  • Pulsating brake feel or altered ABS operation during braking events
  • Occasional false slip/stability interventions

What to check

  • Read all stored and pending ABS/traction codes and freeze frame data with a scan tool
  • Observe live wheel speed sensor data for all four wheels at low rolling speed
  • Visually inspect right rear sensor, connector, wiring and tone ring for damage, corrosion or debris
  • Check for play in wheel bearing and correct sensor air gap to reluctor/tone ring
  • Wiggle harness and connector while watching live data to find intermittent faults
  • Measure sensor resistance (for passive sensors) and supply/pull-up voltages (for active/Hall sensors) at the connector

Signal parameters

  • Passive (magnetic) sensor: DC resistance often ~800–3,000 Ω (varies by vehicle). Produces AC voltage that increases with wheel speed (typical low-speed AC ~0.2–2.0 VAC).
  • Active (Hall/active) sensor: requires reference supply (commonly 5V or 12V) and provides a digital square or pulse output (0–5V or 0–12V) at a frequency proportional to wheel speed.
  • Typical pulse frequency: low speeds tens of Hz, rising with wheel RPM; exact values are vehicle-specific — compare to other wheel sensors.
  • Expected behavior: stable, symmetrical waveform without dropouts or high noise; no open circuit (OL) on resistance check for passive sensors.

Diagnostic algorithm

  1. Connect a scan tool and record C1020 and any related codes; note freeze frame and live wheel speed values.
  2. Verify vehicle-specific sensor type (passive vs active) from service data before electrical tests.
  3. Perform a visual inspection of the right rear sensor, tone ring/reluctor and harness — repair obvious damage or contamination.
  4. With wheel supported and rotated, observe live sensor data. If the right rear shows zero or erratic pulses while others are normal, suspect sensor/hardware or wiring.
  5. For passive sensors: disconnect sensor and measure DC resistance at the sensor leads; compare to spec or the opposite wheel. Check for open/short to ground.
  6. For active sensors: verify reference voltage/pull-up at the sensor connector with key on; then backprobe signal while rotating wheel — expect digital pulses.
  7. Use an oscilloscope to verify waveform integrity (amplitude, symmetry, no dropouts).
  8. Perform a wiggle/rock test on harness and connector while observing live data to find intermittent faults.
  9. Inspect and measure continuity and resistance of wiring back to ABS module; check grounds and connector pins for corrosion or bent pins.
  10. If wiring and sensor test good, swap right rear sensor with an identical known-good sensor (or swap with left rear if same type) and see if fault follows the sensor.
  11. Repair or replace failed sensor, damaged wiring, corroded connector, or damaged tone ring as indicated. Repair grounds and module connectors if faulty.
  12. Clear codes and perform a test drive to confirm repair; re-scan to ensure C1020 does not return.

Likely causes

  • Wiring harness damage or connector corrosion at right rear sensor
  • Failed right rear wheel speed sensor
  • Damaged or missing tone ring on right rear hub
  • Ground or power feed problem to sensor

Fault status

⚠️ Status
Right Rear Wheel Speed Sensor Circuit Malfunction detected. ABS/traction control may be disabled; the fault indicates an open/short/intermittent or invalid signal from the right rear wheel speed sensor circuit.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

C0035 C0040 C0045 C0050 P0500
856

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MERCEDES-BENZ

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