U0420

Code

LAND ROVER U — Network/User

Invalid data received from the power steering control module

Brand: LAND ROVER

Type: U — Network/User

Views: UK: 31 EN: 191 RU: 89

AI status

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Page language: EN

Causes

CAN bus communication fault (physical layer)
Faulty power steering control module (PSCM)
Damaged wiring or connectors to PSCM
Incorrect module programming or calibration
Low battery voltage or poor ground
Intermittent connector corrosion or water ingress

Symptoms

Power steering warning lamp or message on instrument panel
Loss or reduction of power-assisted steering (heavy steering)
Intermittent or erratic steering assist
Other module warnings or communication-related messages present
DTC present in scan tool data for PSCM and possibly other modules

What to check

Read and record all current and stored DTCs from PSCM and other modules on the same CAN network
Check vehicle battery condition and charging system voltage (key-on and cranking)
Visually inspect PSCM connector and CAN wiring for damage, corrosion, pin push-out or water ingress
Check for aftermarket electronics or recent repairs that may have disturbed CAN wiring
Use a scan tool to view live CAN messages and PSCM data (steering angle, assist level, torque request)
Confirm module software/calibration version and recent software updates or reflash history

Signal parameters

CAN bus (High/Low) differential voltage: approx. 2.5 V idle common mode, ±2.5 V differential under drive — confirm with scope or CAN tester
Message frequency: PSCM messages typically periodic (e.g., 10–100 Hz depending on parameter) — check for missing messages
Message contents to monitor: steering wheel angle, assist torque demand, assist level, PSCM status/fault flags
Expected ranges: steering angle, torque values and assist commands should be within plausible physical limits and change smoothly with wheel movement
Error frames and bus load: check for excessive error frames, high bus load or collisions

Diagnostic algorithm

Connect a capable OEM or professional scan tool and retrieve all codes and freeze-frame data from PSCM and other modules
Document which modules report communication or invalid data — helps isolate whether PSCM is source or recipient
Verify battery voltage and ground connections; charge battery if low and clear transient errors then re-scan
Visually inspect PSCM connector, seals and wiring harness for damage, corrosion, tensioned wires or recent repair evidence; repair as needed
Perform a wiggle test on harness/connector while monitoring live data for message dropouts or value jumps
Use a CAN bus physical-layer tester or oscilloscope to check CAN_H and CAN_L for proper recessive/dominant voltages, waveforms, and absence of excessive noise or reflections
If physical layer is good, monitor PSCM message IDs and payload with a logger — look for malformed frames, out-of-range values or unexpected message sources
Compare live steering-related parameters (steering angle, torque request) between PSCM and other modules (ABS, ECU) to identify conflicting data sources
Check for and apply any applicable software updates or reprogramming for PSCM and related modules per manufacturer service information
If wiring and software are confirmed good, follow manufacturer procedure to test or replace PSCM; replace only after confirming fault is internal to module
After repair, clear codes and road test while monitoring live data to verify the fault does not return

Likely causes

Open/short or high-resistance in CAN H/L wiring to PSCM
Corroded, loose or damaged PSCM connector pins
Failed PSCM internal electronics or firmware corruption
Vehicle battery voltage dips during key-on/engine cranking
Faulty steering angle sensor or related sensor feeding PSCM
ECU(s) on same CAN segment transmitting invalid frames

Fault status

⚠️ Status

Invalid or implausible steering data received from the power steering control module; communication or data integrity failure detected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5 - 3.0 hours

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U0420 — Invalid data received from the power steering control module