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Home / DTC / C1256 — Rear Right(RR) Height Sensor Abnormal | EMS Indicates CAN Engine Torque Intervention Fault

C1256 — Rear Right(RR) Height Sensor Abnormal | EMS Indicates CAN Engine Torque Intervention Fault

Detailed page for trouble code C1256.

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C1256

HYUNDAI C — Chassis

Rear Right(RR) Height Sensor Abnormal | EMS Indicates CAN Engine Torque Intervention Fault

Brand: HYUNDAI
Type: C — Chassis
Views: UK: 26 EN: 38 RU: 21
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Page language: EN

Causes

  • Faulty rear right height/position sensor (open, shorted, out-of-range)
  • Damaged wiring or connector at RR height sensor (corrosion, bent pins, broken wire)
  • Incorrect sensor mechanical linkage or seized/damaged suspension link
  • Faulty suspension/height control module (BCM/ASC/AVN module)
  • CAN bus faults between suspension module and EMS (shorts, opens, missing termination)
  • Low battery voltage, poor ground, or blown fuse affecting sensors or modules

Symptoms

  • Suspension warning lamp or height control warning on dash
  • Vehicle ride height incorrect at rear right (sagging or stiff)
  • ABS/ESC or traction control warnings if systems share data
  • Reduced engine power / torque intervention message or limp mode if EMS intervenes
  • Harsh or uneven ride, possible noise from rear suspension
  • Intermittent faults that may clear and return

What to check

  • Read and record all stored and pending DTCs from suspension/BCM, ABS, and EMS modules; note freeze frame/live data
  • Visually inspect RR height sensor, linkage and connector for damage, corrosion, water intrusion, or disconnected harness
  • Wiggle harness and connector while monitoring for intermittent code or live-data changes
  • Measure battery voltage and inspect fuses/grounds for modules involved
  • Compare RR sensor live readings to other height sensors (LF, RF, LR) with scan tool
  • Check CAN bus physical layer: voltage levels, continuity, and termination (approx. 60 ohm between CAN H & CAN L at module ends or 120 ohm across the bus)

Signal parameters

  • Height sensor power: typically 5 V reference supply (verify with scan tool/wiring diagram)
  • Height sensor output: typically a variable voltage (approx. 0.5–4.5 V) that changes with suspension position — values vary by model, compare to other corners
  • Sensor resistance: if a potentiometer-type sensor, resistance should change smoothly with suspension movement (no open circuits)
  • CAN bus idle voltages: CAN High ~2.5 V (dominant ~3.5 V), CAN Low ~2.5 V (dominant ~1.5 V) — measure with meter/oscilloscope
  • Termination resistance across CAN H/L: ~60 ohm measured at a module on a two-terminator bus (two 120 ohm in parallel)
  • Packets: suspension/ride height module and EMS exchange CAN messages reporting ride height and torque intervention flags — verify via a capable scan tool or CAN sniffer

Diagnostic algorithm

  1. Retrieve all stored codes from all modules (BCM/suspension, ABS, EMS). Note any U-codes or communication errors. Clear codes and see if C1256 returns.
  2. Inspect the RR height sensor, linkage and connector for physical damage, corrosion, water ingress or disconnected pins. Repair or reconnect as needed.
  3. With ignition ON, backprobe the sensor connector: confirm 5 V reference (or specified supply), ground, and measure output voltage while moving the suspension through its range. Compare to factory values or the opposite-side sensor.
  4. If output is open, shorted, or out-of-range, trace wiring back to the module. Check continuity and resistance of each conductor. Repair wiring or connector faults.
  5. If sensor voltages are correct, check suspension control module power and ground integrity and inspect its connector. Verify module communicates on CAN bus.
  6. Test CAN bus: measure idle voltages on CAN H and CAN L. Check for proper termination resistance. If CAN communication errors (U-codes) appear, isolate by disconnecting modules one at a time and rechecking bus behavior.
  7. If wiring and CAN bus are good, compare ride height sensor readings across all four corners via scan tool. If only RR is abnormal, replace the RR sensor and retest.
  8. If replacement sensor does not clear the code, consider reprogramming or replacing the suspension/height control module and re-run adaptations/calibrations per factory procedure.
  9. After repairs, clear codes, perform required learning/adaptation procedures for ride height sensors, and road/test to confirm no return of code and proper ride/engine behavior.
  10. If EMS torque intervention flag persists, retrieve EMS data to identify the cause of torque reduction request (stability event, fault condition) and diagnose EMS-related codes separately.

Likely causes

  • RR height sensor failure or connector/wiring fault (most common)
  • Corroded or intermittent connector at the suspension module
  • CAN bus wiring issue (short to battery/ground or open) causing false torque-intervention flag
  • Faulty suspension control module or EMS communication fault
  • Mechanical sensor linkage jammed or misadjusted producing invalid readings

Fault status

⚠️ Status
C1256 — Rear Right height sensor abnormal; suspension module reports EMS requested CAN engine torque intervention. Check RR sensor, wiring/CAN, and module communications.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

Similar codes

C1257 C1260 C1241 U0100 U0073
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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