C1A85

Code

LAND ROVER C — Chassis

Manufacturer-specific DTC — consult Land Rover service manual

Brand: LAND ROVER

Type: C — Chassis

Views: UK: 17 EN: 33 RU: 23

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Causes

Intermittent or permanent loss of communication between modules (CAN/LIN)
Faulty control module hardware or internal electronics
Damaged wiring harness, chafed wires, or intermittent connector connection
Corroded or contaminated connector terminals (water ingress)
Low or unstable battery/vehicle supply voltage
Incorrect or incomplete software/programming or failed module reflash

Symptoms

One or more warning lights or message center alerts related to the affected system
Loss or reduced functionality of the subsystem controlled by the affected module
Intermittent faults that may clear after ignition cycle or battery disconnect
Stored or active DTCs in addition to C1A85, possibly including communication U-codes
Possible limp-home mode depending on the affected system

What to check

Use a Land Rover-approved diagnostic tool (SDD/Pathfinder or equivalent) to read C1A85, all related codes, and freeze-frame/live data
Determine code status: active/current, intermittent, pending, or historic
Record battery voltage and cranking voltage; ensure charged battery (12.4–12.8 V at rest) before testing
Visually inspect wiring and connectors for damage, corrosion, water ingress and secure fit
Check relevant fuses and relays for continuity and proper operation
Verify module power and ground at the connector (measure pin voltages and ground resistance)

Signal parameters

Module supply voltage at key ON and cranking (expected ~9–16 V depending on state)
Module ground resistance (low-ohms,
CAN bus voltages: CAN_H ~2.5–3.5 V idle, CAN_L ~1.5–1.0 V idle and differential ~2.5 V
Presence/absence of module CAN messages (message IDs) on the bus using an oscilloscope or CAN sniffer
Communication error counters or fault frame counts in the diagnostic tool
Freeze-frame parameters captured when C1A85 set (vehicle speed, engine rpm, ambient temp, battery voltage)

Diagnostic algorithm

Connect a Land Rover factory-level scanner and retrieve all DTCs, freeze-frame and live data. Note related U- and C-codes.
Confirm code status (current vs historic) and attempt to clear codes. See if C1A85 returns immediately or only under certain conditions.
Check battery state of charge and charging system; charge or replace battery if voltage is low and retest.
Visually inspect harnesses and connectors for the suspected module and main CAN junctions; repair any damaged insulation or corroded terminals.
Test module power and ground at the connector with ignition on; measure for correct supply voltage and a good ground reference.
Monitor CAN bus while operating the vehicle or cycling the ignition; look for message loss, high error frames, or voltage abnormalities with a scope or CAN tool.
Perform wiggle/strain tests on wiring while watching live data to reproduce intermittent faults.
Review vehicle history for recent module replacements or software updates; if present, verify correct part number and programming status.
If wiring and power/ground are good and communication issues persist, consult factory diagnostic procedures to run module self-tests and component-level checks. Reflash or reprogram the module only when supported by factory instructions.
Replace the module only after confirming it is the root cause. After repairs, clear codes, perform relearn/coding procedures as required, then road test to verify resolution.

Likely causes

Poor connector contact or water-corroded connector at the implicated module
CAN bus short or open (CAN H/L short to power or ground)
Module has failed electrical components (internal fault)
Vehicle battery low or weak during key-on events causing module to report error
Recent software update or module replacement that requires coding/configuration

Fault status

⚠️ Status

Manufacturer-specific DTC — consult Land Rover service manual and factory diagnostic tool for definition and repair instructions.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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