C1A66

Code

LAND ROVER C — Chassis

Control Module Communication Fault

Brand: LAND ROVER

Type: C — Chassis

Views: UK: 21 EN: 23 RU: 19

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Causes

Loss of power or ground to the affected control module
Blown fuse or failed power distribution component
Open, shorted or high-resistance wiring/connectors on CAN or LIN network
Corroded or water-damaged connector(s)
Network bus off condition caused by a node fault
Faulty control module (internal hardware or software)

Symptoms

Warning lamp(s) illuminated (master warning, specific system warnings)
Affected system(s) inoperative (e.g., doors/locks, lighting, ABS, airbag, infotainment) or reporting 'not available'
Intermittent or permanent loss of diagnostics for the module in a scan tool
Multiple communication-related DTCs stored across modules
Unusual vehicle behavior tied to networked systems (locks, windows, CAN-controlled actuators)

What to check

Use a professional scan tool to read all stored/extended network codes and note which control module(s) are not responding
Check and record battery voltage (engine off and cranking) and inspect battery terminals for corrosion/tightness
Inspect and test fuses and relays powering the affected module and common bus power sources
Visually inspect harnesses and connectors for corrosion, water ingress, damaged insulation, pin push-out or bent pins
Measure CAN High and CAN Low idle voltages with respect to chassis (~2.5 V each) and check differential levels with a scope
Check CAN termination resistance across CAN_H and CAN_L (typical ~60 Ω for two 120 Ω terminators in parallel)

Signal parameters

CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
Differential voltage when dominant ≈ 2.0 V
Bus termination ~60 Ω total (two 120 Ω terminators in parallel)
Typical CAN baud rates: 500 kb/s or 250 kb/s (verify manufacturer network speed)
Expected periodic message IDs and message frequency for the affected module (compare to a known-good vehicle or factory data)
Module error counters / bus-off flag shown in advanced diagnostic data

Diagnostic algorithm

Record DTCs from all modules and take notes of any other network-related codes.
Verify battery condition and connections; recharge or replace battery if voltage inadequate.
Inspect and test fuses/relays for the affected module and related power distribution circuits.
Identify physical location of the module and inspect its connector for corrosion, bent pins, moisture, or damage; disconnect, inspect, and reseat.
With ignition on, use a scan tool to attempt communication with the module; note if module responds after connector manipulation (intermittent contact).
Measure CAN_H/CAN_L voltages at the module connector and at a known-good network point. If voltages are abnormal, isolate wiring between points.
Check termination resistance and use an oscilloscope to view waveform quality; look for excessive noise or missing message activity.
If a short or open is found, repair wiring/harness or replace damaged connectors; protect and seal repaired areas against moisture.
If wiring and power/ground are good but module does not communicate, perform module re-flash/update if available and recommended by OEM.
If reprogramming is unsuccessful and all network tests pass, consider replacing the module. Follow OEM procedures for coding/initialization and re-check the network afterward.
After repair, clear codes and perform a full network scan and road test to confirm the fault does not return.
If intermittent or complex network issues persist, obtain OEM wiring diagrams, module pinouts and manufacturer technical bulletins; escalate to dealer-level diagnostics if required.

Likely causes

Low battery or poor battery connections causing modules to drop off the bus
Blown/loose fuse or connector at the affected module
Damaged CAN high/low pair (short to ground or +12V) in harness sections near known trouble areas (doors, rear modules, underbody)
Corrosion/water ingress at multi-pin connectors causing intermittent comms
Failed gateway or other network module disrupting address claiming

Fault status

⚠️ Status

Control Module Communication Fault — affected module not communicating on vehicle network (CAN/LIN); check power, ground, connectors, and bus wiring.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours

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C1A66 — Control Module Communication Fault