U0425

Code

LAND ROVER U — Network/User

Invalid data received from the auxiliary heater control module

Brand: LAND ROVER

Type: U — Network/User

Views: UK: 12 EN: 30 RU: 15

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Page language: EN

Causes

Faulty auxiliary heater control module (software or hardware)
Corroded, loose or damaged connector(s) at the auxiliary heater module
Open, shorted or high-resistance CAN bus wiring (CAN_H/CAN_L)
Low or intermittent battery voltage or poor ground connection
Blown fuse or faulty relay supplying the heater module
Software incompatibility or corrupted module calibration

Symptoms

Auxiliary heater does not turn on or does not respond to commands
Driver warning lamp or message about heater or climate preconditioning
No cabin pre-heat / loss of remote pre-heat function
Intermittent operation of heater or sporadic restoration after key cycle
Related control units report communication faults or fail to show expected heater data

What to check

Read all stored DTCs and freeze frame data from the vehicle and auxiliary heater module
Confirm battery voltage is within specification during cranking and diagnosis (use a battery support if required)
Inspect fuses and relays supplying the auxiliary heater circuit
Visually inspect connector(s) and wiring to the auxiliary heater for corrosion, bent pins, water damage, or rubbing/abrasion
Check general CAN bus health: ensure other modules communicate normally and note any other U-codes
Verify module supply and ground circuits for continuity and resistance

Signal parameters

CAN bus physical: CAN_H and CAN_L twisted pair; idle common-mode ~2.5 V
Expected dominant differential ~1.5–3.0 V when messages transmit (verify with oscilloscope)
Typical periodic auxiliary heater status message: low-frequency periodic messages (eg 1–10 Hz) carrying status bytes — message ID and payload are manufacturer-specific
Message payload fields commonly include: heater demand, fault flags, relay/valve status, temperature readings
Timing: messages should be periodic and consistent; missing or corrupt frames and high error counters indicate bus problems
Noisy bus or stuck dominant state will block multiple modules from communicating

Diagnostic algorithm

Record U0425 and any related codes from all modules; note freeze frame and battery voltage at fault time
Verify battery state and health; if battery voltage is low or unstable, recharge or use a diagnostic power supply before further testing
Perform a visual inspection of the auxiliary heater module connectors and wiring for corrosion, water ingress, loose or damaged pins
Inspect and test fuses and relays for the heater module power feed; replace if suspect
With ignition on, verify module power and ground at the connector with a multimeter (reference wiring diagram). Repair any supply or ground issues
Scan the CAN bus: check for other communication faults (U0100, U0121, etc.). Use a scope to observe CAN_H and CAN_L for expected idle voltage, message activity, and noise/spikes
If bus shows a stuck dominant line or heavy errors, isolate segments by disconnecting suspected nodes (disconnect auxiliary heater connector) and re-check bus behavior
If wiring and bus are correct and supply is stable, attempt to re-establish communication: cycle ignition and perform a module reset if supported by the manufacturer's tool
Check for available software updates or calibration reprogramming for the auxiliary heater module; re-flash only with the correct procedure and battery support
If module still reports invalid data after verifying wiring, power and software updates, consider replacing the auxiliary heater control module. Re-test and clear codes; confirm normal operation and that no other modules report communication errors
Document repairs and advise customer about potential intermittent faults if the cause was corrosion or moisture
If uncertain, consult Land Rover technical service information or dealer-level diagnostics for manufacturer-specific message IDs and diagnostics

Likely causes

Poor electrical supply or ground to the auxiliary heater module
Connector corrosion or pin damage at the auxiliary heater module
CAN bus wiring short to battery/ground or to other circuits
Module internal failure or corrupted firmware following a power event
Conflicting or missing CAN messages due to a failed gateway or intermediate module

Fault status

⚠️ Status

Module is transmitting invalid or out-of-spec data on the vehicle CAN network; communication/data integrity with the auxiliary heater control module has failed.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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U0425 — Invalid data received from the auxiliary heater control module