C0047 — Left-Rear (LR) Wheel Speed Sensor Circuit Low / Signal Low

Note: Exact wording varies by OEM. “Circuit Low” or “Signal Low” indicates the module sees low voltage/low amplitude from the LR sensor circuit, distinct from a pure “open” or “short” code.

What it means

The ABS/EBCM detects the LR wheel-speed signal is below calibrated voltage or amplitude, often due to a weak sensor, excessive air gap, encoder damage, or voltage drop in the LR harness/connector path. On platforms using active sensors, “circuit low” can also point to short-to-ground or an internal sensor failure pulling the signal low. JustAnswer+1

Typical symptoms

  • ABS lamp; ESC/traction disabled messages possible.
  • Intermittent low-speed ABS activation (chatter) if the waveform is noisy or weak.

Common root causes

  • Weak/failed LR sensor (internal fault or contamination).
  • Excessive air gap or damaged encoder in the RR hub assembly.
  • Wiring/connector issues producing a voltage drop or partial short-to-ground at the knuckle or along the rear harness. JustAnswer

Professional diagnostics (step-by-step)

  1. Live-data comparison
    • Graph all four wheel speeds; a chronically lower or dropping LR trace indicates low-signal behavior.
  2. Scope the sensor
    • Active sensor: verify supply and ground, then view the square-wave amplitude; a stuck-low or narrow-swing waveform confirms “signal low.”
    • Inductive sensor: spin the wheel and check AC amplitude; compare LR vs. RR. Weak AC on LR with good RR = LR corner issue.
  3. Air-gap and encoder
    • Measure/check the sensor seating depth and the condition of the encoder ring. Correct gap; replace the hub if the encoder is damaged.
  4. Circuit integrity
    • LR harness is exposed to spray/road debris; unplug both ends and test for short-to-ground, short-to-B+, high resistance. Repair any compromised sections.
  5. Relearn/verification
    • Clear codes, road-test with live data; verify stable, matched wheel-speed traces.

Verified fixes

  • Replace the LR wheel-speed sensor when amplitude remains low after cleaning/seating.
  • Correct air gap, or replace hub/encoder if physically damaged.
  • Repair/repin the LR harness/connector to remove voltage drop/partial short-to-ground.
  • Only after inputs/harness pass, evaluate the EBCM. JustAnswer

Sources:

  • Technician Q&A and service-procedure guidance for C0047 = LR signal low/low voltage, highlighting sensor vs. harness root-causes and verification by scope/voltage testing. JustAnswer
  • Field example mapping C0047 to LR wheel-speed low circuit diagnostics (post-replacement persistence → harness inspection). JustAnswer