U1550 — No message received from power steering

Causes

• Blown fuse or tripped relay supplying power to the EPS module
• Loss of power or ground at the EPS module
• Damaged or corroded connector at the EPS unit
• Broken, shorted or high-resistance CAN bus wiring between EPS and other modules
• CAN bus termination resistor open or missing
• EPS module internal fault or failed module

Symptoms

• EPS warning lamp or general warning light on instrument cluster
• Reduced or no power-assisted steering (heavy manual steering)
• Steering assist intermittent or erratic
• Other CAN-related warnings or instruments showing communication errors
• Possible drivability or electronic stability systems alerts if they rely on EPS data

What to check

• Verify battery voltage is stable (12V+ with ignition on) and battery connections are clean/tight
• Inspect fuses and relays related to power steering; replace if blown
• Visually inspect EPS module connector for corrosion, bent pins, water intrusion, or loose terminals
• Use a scan tool to read all network modules and note which modules report 'no CAN communication' or timeouts
• Check for additional DTCs in EPS, BCM, ABS and instrument cluster that indicate network issues
• Measure supply voltage and ground at the EPS module connector with ignition on

Signal parameters

• Vehicle battery supply to EPS: ~12 V (with ignition on); no large voltage drop under load
• EPS ground: low resistance to chassis ground; no intermittent connection
• CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (measured to ground); differential ~0 V when recessive
• CAN dominant state: CAN_H rises and CAN_L falls giving differential ~1–3 V during activity (use oscilloscope)
• Message frequency: EPS typically transmits periodic status/torque messages (several Hz to tens of Hz); absence indicates fault
• CAN bus nominal baud rates: commonly 500 kb/s or 250 kb/s depending on vehicle architecture (confirm for model)

Similar codes