C1047

Code

FIAT C — Chassis

Left rear wheel speed sensor

Brand: FIAT

Type: C — Chassis

Views: UK: 23 EN: 54 RU: 24

AI status

Completed

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Page language: EN

Causes

Failed left rear wheel speed sensor (internal short/open)
Damaged or contaminated tone/reluctor ring at left rear hub
Corroded, loose or disconnected sensor connector
Broken, chafed or shorted wiring harness between sensor and ABS module
Poor ground or supply/reference fault for an active sensor
Intermittent connection from water/road contamination

Symptoms

ABS warning lamp illuminated
Traction control / stability control warning or reduced function
Intermittent or incorrect wheel-speed reading for left rear in scanner live data
ABS may engage incorrectly or not engage when required
Possible speedometer or cruise control irregularities (if vehicle uses wheel speed for those systems)

What to check

Retrieve and record freeze frame and stored data with a diagnostic scanner (wheel speed inputs, related codes)
Visually inspect left rear sensor, connector and wiring for damage, corrosion, pin deformation and moisture intrusion
Inspect the reluctor/tone ring on the hub/axle for missing teeth, heavy corrosion, debris or magnetized metal shavings
Compare live wheel speed readings for all four wheels at low speed (on lift or road test) to identify dropouts or no signal from left rear
Wiggle test harness and connector while monitoring live data to find intermittent faults
Measure sensor resistance with a DVM (for passive/VR sensors) and compare to spec; check for short to ground/short to power

Signal parameters

Passive (variable reluctance) sensor: generates AC voltage. Typical behavior — low speed: ~0.1–1.0 Vrms; higher speed: several volts peak-to-peak; frequency proportional to wheel RPM
Passive sensor DC resistance (typical range): few hundred ohms to a few kilo-ohms depending on design — compare to OEM spec
Active (Hall/electronic) sensor: provides square/pulse output, typically 0–5V (some systems use 0–12V). Output switches with wheel rotation; frequency proportional to RPM
Typical pulse frequency: proportional to wheel speed; nominal pulses per wheel revolution determined by tone ring tooth count (refer to vehicle spec)
Sensor air gap: small clearance (often 0.5–2.0 mm) — excessive gap reduces signal amplitude

Diagnostic algorithm

Connect an OBD scanner and read stored codes and live wheel-speed data. Note whether C1047 is current or historic and any related ABS/traction codes.
Visually inspect left rear sensor, connector and wiring for obvious damage, corrosion, water intrusion or foreign material. Clean connector and dry if needed.
With ignition ON (engine off), backprobe sensor connector and confirm reference supply and ground presence for active sensors (compare to OEM values). Do NOT short pins.
Measure sensor DC resistance (for passive sensors) with meter disconnected. If open or out of spec, replace sensor.
Rotate wheel by hand (lifted) or use driven method and measure AC output (passive) or pulse output (active) with oscilloscope or DVOM (frequency/voltage should increase with speed).
Wiggle harness and connector while spinning wheel and watching live data for intermittent changes. Repair any broken wires or poor terminals.
Inspect the reluctor/tone ring for missing teeth, heavy rust, spacing issues or metal debris. Replace or repair if damaged and ensure correct air gap between sensor tip and ring.
Verify continuity between sensor connector and ABS module pins; check for shorts to power/ground. Repair wiring harness as required.
If sensor, connector and wiring test good, scan and test the ABS module inputs; consider module fault if input stage is defective. Consult OEM procedures before module replacement.
After repairs, clear codes and perform a road test or roller test to confirm proper wheel speed readings and that the ABS/traction warnings do not return.

Likely causes

Faulty left rear wheel speed sensor
Connector corrosion or loose pin at left rear sensor
Damaged reluctor/tone ring (missing teeth, heavy rust/debris)
Wiring harness damage between sensor and ABS module

Fault status

⚠️ Status

Left rear wheel speed sensor circuit fault detected — left rear wheel speed signal out of range, missing or intermittent.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 1.5 hours

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