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Home / DTC / C1A85 — Manufacturer-specific DTC — consult Land Rover service manual

C1A85 — Manufacturer-specific DTC — consult Land Rover service manual

Detailed page for trouble code C1A85.

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C1A85

LAND ROVER C — Chassis

Manufacturer-specific DTC — consult Land Rover service manual

Brand: LAND ROVER
Type: C — Chassis
Views: UK: 3 EN: 5 RU: 5
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Page language: EN

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

  1. Connect a Land Rover factory-level scanner and retrieve all DTCs, freeze-frame and live data. Note related U- and C-codes.
  2. Confirm code status (current vs historic) and attempt to clear codes. See if C1A85 returns immediately or only under certain conditions.
  3. Check battery state of charge and charging system; charge or replace battery if voltage is low and retest.
  4. Visually inspect harnesses and connectors for the suspected module and main CAN junctions; repair any damaged insulation or corroded terminals.
  5. Test module power and ground at the connector with ignition on; measure for correct supply voltage and a good ground reference.
  6. 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.
  7. Perform wiggle/strain tests on wiring while watching live data to reproduce intermittent faults.
  8. Review vehicle history for recent module replacements or software updates; if present, verify correct part number and programming status.
  9. 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.
  10. 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

Similar codes

C1A84 C1A86 U0100 U0121 U0155
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