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Home / DTC / U012B — Lost communication with the chassis control module B

U012B — Lost communication with the chassis control module B

Detailed page for trouble code U012B.

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Code

U012B

LAND ROVER U — Network/User

Lost communication with the chassis control module B

Brand: LAND ROVER
Type: U — Network/User
Views: UK: 3 EN: 6 RU: 8
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Page language: EN

Causes

  • Faulty or corroded connector at the Chassis Control Module B
  • Open, shorted or high-resistance CAN bus wiring (CAN High/CAN Low) to the module
  • Module power (fuse, supply) or ground missing or intermittent
  • Missing or faulty CAN termination resistor(s)
  • Module in sleep mode, not awake, or software/firmware mismatch
  • Faulty CCMB module

Symptoms

  • Illumination of warning lamp(s) related to chassis systems (ABS/traction/stability)
  • Loss or degradation of functions managed by CCMB (stability control, active suspension, etc.)
  • Other modules reporting their own communication DTCs
  • Scan tool cannot communicate with CCMB or shows the module as 'not present'
  • Intermittent faults that occur when turning, driving or after key cycles

What to check

  • Retrieve all stored DTCs and freeze frame data from all networks; note time/date and mileage
  • Confirm battery voltage is within specification (typically 12–14.5 V) and fully charged
  • Visually inspect CCMB connector(s) for corrosion, bent pins, water ingress or damage
  • Check fuses and power feed to the CCMB and measure module supply and ground at the connector
  • With ignition on, verify CAN bus idle voltages at a known-good connector: CAN_H and CAN_L
  • Measure resistance across CAN_H and CAN_L with power off (expect approx. 60 ohms total for two 120Ω terminators)

Signal parameters

  • Battery / supply voltage to module: approx. 12–14.5 V (should be stable)
  • CAN bus idle voltages (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both near mid-supply)
  • Dominant state voltages: CAN_H typically ~3.5 V and CAN_L ~1.5 V (differential ≈ 2.0 V)
  • Termination resistance (between CAN_H and CAN_L with power off): approx. 60 Ω (two 120 Ω terminators in parallel)
  • Physical continuity: low ohm continuity between module CAN pins and network backbone; no short to battery or ground

Diagnostic algorithm

  1. Record all U-codes and note whether the CCMB is shown as 'not present' or 'no response' on the scan tool.
  2. Verify battery voltage and engine bay power distribution; reconnect battery if necessary and clear codes to see if faults return.
  3. Locate CCMB and identify connector pinout from wiring diagram; check fuses and measure module supply and ground at the connector.
  4. Inspect the CCMB connector for corrosion/water ingress, clean and reseat; repair any damaged pins or terminals.
  5. With ignition ON, measure CAN_H and CAN_L at the module connector. Compare to expected idle/dominant values and to other known-good nodes.
  6. With power off, measure resistance across CAN_H and CAN_L: expect approx. 60 Ω. If open or very low, investigate missing terminator or short.
  7. Isolate the fault by disconnecting the CCMB and observing whether bus behavior changes; disconnect other nodes one at a time if required to find a faulting module.
  8. Perform a wiggle test on harnesses and connectors while monitoring communication to find intermittent breaks.
  9. If wiring and power/ground check OK and bus activity present, attempt communication using manufacturer diagnostic routines: wake the module, reflash/update software if indicated, or run module self-test.
  10. If CCMB still does not communicate and wiring/power are verified good, consider replacing the CCMB or sending it for repair/reprogramming per manufacturer procedures.
  11. After any repair, clear DTCs and perform road test/cycle ignition to confirm fault does not return; re-scan all networks.

Likely causes

  • Power or ground fault at the CCMB (blown fuse, loose ground)
  • Damaged or corroded connector/wiring at the CCMB
  • CAN bus open, short to voltage/ground, or failed termination
  • CCMB hardware failure or internal fault
  • Intermittent network node (another control module) causing bus errors

Fault status

⚠️ Status
No response or interrupted messages from Chassis Control Module B on the vehicle data bus (CAN).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3.0 hours

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U0100 U0121 U0140 U0155 U0422
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