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Home / DTC / C1206 — FL wheel speed sensor signal

C1206 — FL wheel speed sensor signal

Detailed page for trouble code C1206.

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C1206

MITSUBISHI C — Chassis

FL wheel speed sensor signal

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

Causes

  • Damaged or failed front-left wheel speed sensor
  • Broken, shorted or corroded sensor wiring or connector
  • Contaminated or corroded connector pins
  • Damaged or missing reluctor (tone) ring or magnetic pickup surface
  • Wheel bearing or hub damage causing improper air gap
  • Interference from debris or metal shavings near the sensor

Symptoms

  • ABS warning lamp illuminated
  • Traction control / stability control warning lamp illuminated or disabled
  • ABS function inoperative or reduced
  • Erratic or no FL wheel speed value in scan-tool live data
  • Possible speedometer/gear shift anomalies on some vehicles
  • Possible unusual noise or play from front-left wheel/hub

What to check

  • Scan for additional ABS or wheel speed codes and record freeze frame/live data
  • Visual inspection of FL sensor, connector, and wiring for damage, corrosion, or contamination
  • Check connector pins for corrosion, bent pins, or loose terminals
  • Compare FL wheel speed live data to other wheels at low speed
  • Check for proper sensor supply voltage/reference and ground (if active sensor)
  • Measure sensor resistance (for passive sensors) and continuity to ABS module

Signal parameters

  • Passive (magnetic) sensor: generates AC waveform; amplitude increases with wheel speed (millivolts to volts) and frequency proportional to speed.
  • Active (Hall or magnetoresistive) sensor: produces digital pulses (square wave) referenced to vehicle electronics (commonly 0–5V or 0–12V) with frequency proportional to wheel speed.
  • Resistance check (passive sensor): vehicle-specific—refer to service manual; abnormal open or short indicates sensor failure.
  • Waveform check: clean, regular pulses without dropout, jitter or excessive noise. Missing pulses or irregular amplitude indicates sensor/reluctor/wiring issue.

Diagnostic algorithm

  1. Read ABS/vehicle codes and note any related codes and freeze-frame data. Clear codes and see if C1206 returns.
  2. With ignition ON, inspect FL sensor connector and wiring for corrosion, bent pins, damage, chafing, or moisture. Repair or clean as needed.
  3. Use a scan tool to monitor FL wheel speed value while slowly rolling the vehicle; compare to other wheel speeds. Look for dropouts or no reading.
  4. Backprobe connector: check sensor reference/power and ground (active sensor) or measure resistance across sensor terminals (passive sensor). Compare to factory spec.
  5. Spin the wheel and observe the sensor signal with an oscilloscope (preferred) or AC voltmeter. Confirm consistent waveform and amplitude that changes with speed.
  6. If signal is missing or erratic, wiggle wiring and connector while observing signal to check for intermittent faults.
  7. Inspect the reluctor/tone ring for missing teeth, heavy rust, or debris. Check air gap between sensor and ring; adjust or replace if out of spec.
  8. Check hub/bearing for excessive play that could change sensor gap; repair as required.
  9. If wiring and sensor tests fail, swap FL sensor with a known-good wheel sensor (if same type) and re-check to isolate sensor vs harness/module.
  10. If swapped sensor works, replace the original FL sensor and retest. If fault follows harness, repair or replace wiring/connector.
  11. If all external tests pass and no wiring fault found, consider ABS module fault and follow manufacturer procedures for module diagnosis or replacement.

Likely causes

  • Open or short in FL sensor harness or connector
  • Failed FL wheel speed sensor (internal open/short or weak output)
  • Reluctor ring damaged, missing teeth, or excessive runout
  • Connector corrosion or poor mating
  • Intermittent wiring due to chafing at suspension joint
  • Less likely: ABS module fault

Fault status

⚠️ Status
Front-left wheel speed sensor signal fault detected. ABS/traction control module reports invalid, intermittent, or missing FL wheel speed input.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

C1201 C1202 C1203 C1204 C1205 C1207
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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