U1340

Code

Generic U — Network/User

Steering Angle Sensor: No Communication

Brand: Generic

Type: U — Network/User

Views: UK: 9 EN: 9 RU: 8

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty or failed steering angle sensor/module
Damaged wiring or connector in steering column harness (including clock spring)
Open or short on CAN/LIN bus (to battery or ground)
Missing or low sensor power or ground (blown fuse, bad splice)
Poor termination or wiring high resistance on the vehicle network
Intermittent connection from steering wheel movement or corrosion

Symptoms

ABS, ESC, or traction control warning lamp illuminated
Loss of stability control, lane-keeping, or other driver aids that use steering angle
Steering angle value missing or frozen on scan tool
Inconsistent or no steering wheel position shown in instrument cluster
Multiple communication-related DTCs present
Intermittent faults that occur when steering wheel is turned

What to check

Read all stored and pending DTCs from all modules; note freeze-frame data
Verify the steering angle sensor module appears on the network with a scan tool
Check for related U-codes on gateway/ABS/BCM/ECU indicating bus issues
Inspect steering column wiring, clock spring and connectors for damage or corrosion
Verify sensor power and ground at the connector (voltage and continuity)
Measure CAN_H and CAN_L voltages and differential with key on (see signal_params)

Signal parameters

Typical CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive).
Dominant state during transmission: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ~2.0 V).
Termination resistance between CAN_H and CAN_L (key off) ≈ 60 Ω (two 120 Ω terminators in parallel).
Expected sensor supply: vehicle-specific (commonly 5 V reference or battery/ignition feed); check service data.
Steering angle message rate: vehicle-dependent; typically tens of Hz (10–50 Hz) while steering is moving.
No valid steering angle message or repeated error frames indicate communication failure.

Diagnostic algorithm

Confirm DTC: Connect a capable scan tool and record U1340 and any related codes; capture live data and freeze frame.
Check module presence: Verify the steering angle sensor or its ECU is present and responsive on the network. If absent, proceed to wiring/power checks.
Power/ground check: At the sensor connector, verify correct supply voltage (with key on) and good chassis ground continuity. Repair any open/low circuits.
Inspect harness and connectors: Visually examine steering column harness, clock spring, and connectors for damage, corrosion, or pin push-out. Repair or replace as required.
Network wiring test: With ignition off, measure resistance between CAN_H and CAN_L (~60 Ω). With ignition on, measure DC voltages on CAN_H and CAN_L and look for expected idle voltages.
Monitor network traffic: Use a scan tool or scope to confirm steering angle messages and bus behavior. Look for dominant states, error frames, or missing messages.
Wiggle/test while steering: With the scan tool active, move the steering wheel through its range to see if messages appear or fault is intermittent—this helps locate a broken conductor or clock spring fault.
Isolate bus/device: If possible, disconnect the steering angle sensor and see if other modules report changed bus behavior or error codes. Replace suspect wiring or sensor as diagnosed.
Replace or reprogram: If wiring and power are good but the sensor/module does not communicate, replace the steering angle sensor or reprogram/update module software per service instructions.
Verify repair: Clear codes, perform required calibrations (steering angle reset/calibrate) and confirm the system operates correctly on road test.