Code
U1550
ALFA ROMEO
U — Network/User
No message received from power steering
Views:
UK: 7
EN: 10
RU: 9
AI status
Completed
Completed
100%
Causes
- Faulty Electric Power Steering (EPS) control module
- Open, shorted or high-resistance wiring on CAN H/CAN L to the EPS
- Corroded/damaged connectors at EPS or gateway/BCM
- Blown fuse or loss of power/ground to the EPS module
- CAN bus transceiver failure in EPS or another module
- Network termination or bus wiring fault (missing/incorrect termination resistance)
Symptoms
- Steering system warning lamp or EPS warning in instrument cluster
- Loss of electric power assist or reduced/locked steering assist (may be intermittent)
- ABS/ESC or other networked warning lights may also be present
- Instrument cluster shows communication or module missing messages
- Steering effort increases, especially at low speed
- Possible limp-home mode or limited vehicle drivability
What to check
- Read and record all current and stored DTCs and freeze frame data from all network modules
- Verify battery voltage (key ON) and charging system health (12.0–14.5 V expected)
- Visually inspect EPS connector, wiring harness, and nearby ground points for damage or corrosion
- Check fuses and relays related to EPS and instrument/gateway modules
- Use a scan tool to attempt communication with the EPS module and view live CAN bus traffic
- Measure CAN H and CAN L voltages with key ON engine OFF (see signal_params)
Signal parameters
- Idle voltages (each line to chassis): ~2.5 V (CANH and CANL each near 2.5 V when recessive)
- Dominant bit voltages: CANH ~3.5 V, CANL ~1.5 V (differential ~2.0 V)
- Differential idle voltage ~0 V, dominant ~2.0 V
- Common CAN bus data rates used on Alfa Romeo can be 500 kbps or 250 kbps (vehicle-specific)
- Expected termination: two 120 ohm resistors in parallel → ~60 ohm across CANH and CANL at network ends
Diagnostic algorithm
- Record symptoms and all DTCs from all modules; note occurrence conditions (ignition on, driving, cold start).
- Confirm U1550 is current and reproducible: attempt communication with EPS using OEM-level scanner; note if module appears on network.
- Check vehicle battery voltage and charging — restore proper voltage before further tests.
- Visually inspect EPS connector, wiring, and harness routing for chafing or damage; repair any problems found.
- Check and verify fuses/relays that supply EPS power and any instrument/gateway fuses. Replace if defective.
- With ignition ON (engine OFF) monitor CAN bus traffic on the high-speed network using a scan tool or scope. If no traffic from EPS ID, probe at EPS connector.
- Measure CANH and CANL voltages at EPS connector and at gateway/BCM. Verify termination resistance ~60 ohm across CANH/CANL. Look for short to VBAT or ground.
- If bus voltages or termination are faulty, isolate and repair wiring short/open. Disconnect suspected module(s) to isolate bus fault; check whether bus returns to normal.
- If wiring and power/ground are good but EPS still not present on bus, attempt module reset (power cycle, clear codes) and perform ECU software/parameter check and update if available.
- If a known-good EPS module or harness is available, swap to confirm module fault before replacement.
- After repair, clear codes, verify EPS communication, and perform functional test / road test to confirm normal steering assist and no recurrence of U1550.
Likely causes
- Disconnected or corroded EPS connector at steering column
- Blown 5A/10A/30A fuse feeding EPS (vehicle-specific)
- Damaged CAN wiring harness behind dash or in steering column
- EPS module internal failure (transceiver or processor)
- Vehicle battery recently disconnected or low charge causing module to not wake
- Aftermarket devices or recent repairs disturb CAN wiring
Fault status
Status
No CAN messages received from the power steering control module. Steering assist and related systems may be degraded; communication with EPS is lost or intermittent.
Repair difficulty: Medium
Diagnostic time: 1.5-3.5 hours
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Code
U1550
FIAT
U — Network/User
No message received from power steering
Views:
UK: 4
EN: 10
RU: 6
AI status
Completed
Completed
100%
Causes
- Faulty Electric Power Steering (EPS) control module
- Open, shorted or high-resistance wiring on CAN H/CAN L to the EPS
- Corroded/damaged connectors at EPS or gateway/BCM
- Blown fuse or loss of power/ground to the EPS module
- CAN bus transceiver failure in EPS or another module
- Network termination or bus wiring fault (missing/incorrect termination resistance)
Symptoms
- Steering system warning lamp or EPS warning in instrument cluster
- Loss of electric power assist or reduced/locked steering assist (may be intermittent)
- ABS/ESC or other networked warning lights may also be present
- Instrument cluster shows communication or module missing messages
- Steering effort increases, especially at low speed
- Possible limp-home mode or limited vehicle drivability
What to check
- Read and record all current and stored DTCs and freeze frame data from all network modules
- Verify battery voltage (key ON) and charging system health (12.0–14.5 V expected)
- Visually inspect EPS connector, wiring harness, and nearby ground points for damage or corrosion
- Check fuses and relays related to EPS and instrument/gateway modules
- Use a scan tool to attempt communication with the EPS module and view live CAN bus traffic
- Measure CAN H and CAN L voltages with key ON engine OFF (see signal_params)
Signal parameters
- Idle voltages (each line to chassis): ~2.5 V (CANH and CANL each near 2.5 V when recessive)
- Dominant bit voltages: CANH ~3.5 V, CANL ~1.5 V (differential ~2.0 V)
- Differential idle voltage ~0 V, dominant ~2.0 V
- Common CAN bus data rates used on Alfa Romeo can be 500 kbps or 250 kbps (vehicle-specific)
- Expected termination: two 120 ohm resistors in parallel → ~60 ohm across CANH and CANL at network ends
Diagnostic algorithm
- Record symptoms and all DTCs from all modules; note occurrence conditions (ignition on, driving, cold start).
- Confirm U1550 is current and reproducible: attempt communication with EPS using OEM-level scanner; note if module appears on network.
- Check vehicle battery voltage and charging — restore proper voltage before further tests.
- Visually inspect EPS connector, wiring, and harness routing for chafing or damage; repair any problems found.
- Check and verify fuses/relays that supply EPS power and any instrument/gateway fuses. Replace if defective.
- With ignition ON (engine OFF) monitor CAN bus traffic on the high-speed network using a scan tool or scope. If no traffic from EPS ID, probe at EPS connector.
- Measure CANH and CANL voltages at EPS connector and at gateway/BCM. Verify termination resistance ~60 ohm across CANH/CANL. Look for short to VBAT or ground.
- If bus voltages or termination are faulty, isolate and repair wiring short/open. Disconnect suspected module(s) to isolate bus fault; check whether bus returns to normal.
- If wiring and power/ground are good but EPS still not present on bus, attempt module reset (power cycle, clear codes) and perform ECU software/parameter check and update if available.
- If a known-good EPS module or harness is available, swap to confirm module fault before replacement.
- After repair, clear codes, verify EPS communication, and perform functional test / road test to confirm normal steering assist and no recurrence of U1550.
Likely causes
- Disconnected or corroded EPS connector at steering column
- Blown 5A/10A/30A fuse feeding EPS (vehicle-specific)
- Damaged CAN wiring harness behind dash or in steering column
- EPS module internal failure (transceiver or processor)
- Vehicle battery recently disconnected or low charge causing module to not wake
- Aftermarket devices or recent repairs disturb CAN wiring
Fault status
Status
No CAN messages received from the power steering control module. Steering assist and related systems may be degraded; communication with EPS is lost or intermittent.
Repair difficulty: Medium
Diagnostic time: 1.5-3.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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👍 Like
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Send to email