Code
U2143
OPEL
U — Network/User
CAN-Bus No Communication with SAS (Steering Angle Sensor)
Views:
UK: 5
EN: 9
RU: 4
AI status
Completed
Completed
100%
Causes
- Open, shorted or corroded wiring/connectors between SAS and CAN bus
- Faulty steering angle sensor (internal failure)
- Loss of sensor power or ground (blown fuse, open circuit)
- CAN bus short to battery/ground/5V or high resistance in bus
- Missing or failed CAN termination resistor(s)
- Intermittent contact due to damaged connector or harness movement
Symptoms
- ABS/ESP/traction control warning lamp illuminated
- Steering angle not shown in scan tool live data
- Loss of vehicle stability or traction-assist functions
- Adaptive chassis/steering features disabled
- Cruise control or lane-assist features inhibited
- One or more related communication U-codes present
What to check
- Read and record all stored DTCs and freeze-frame data; note any other U-codes
- Visually inspect SAS connector and wiring for corrosion, damage, or water ingress
- Check fuses and power/ground circuits for the SAS
- Verify presence/absence of SAS messages using a scan tool (live data / bus traffic)
- Measure CAN_H and CAN_L voltages at the SAS connector with key ON, engine off
- Check termination resistance across CAN_H and CAN_L (≈60 ohms typical with two 120Ω resistors)
Signal parameters
- Idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both lines near mid-supply)
- Dominant state: CAN_H typically rises ~3.5–4.5 V, CAN_L falls ~0.5–1.5 V (so differential ≈2–3.5 V)
- Typical termination: two 120 Ω resistors in parallel = ~60 Ω across CAN_H to CAN_L
- Common bus speeds: high-speed CAN ~500 kbps (vehicle dependent); low-speed CAN ~125 kbps
- No SAS traffic visible on bus when U2143 is active
Diagnostic algorithm
- Confirm the fault: Clear codes and see if U2143 returns. Record any accompanying U-codes.
- Check other modules on the same CAN network to determine if the fault is isolated to the SAS or system-wide loss of comms.
- Visually inspect the SAS connector, wiring, and nearby harness for damage, corrosion, or moisture. Repair any physical damage.
- Verify power and ground at the SAS connector with key ON. Check related fuses and relays.
- Measure CAN_H and CAN_L voltages at the SAS connector. Compare to expected idle voltages. Check termination resistance between lines (≈60 Ω).
- Use an oscilloscope or high-speed CAN diagnostic tool to look for CAN frames and noise on the bus while turning the steering wheel (some SAS messages are produced with steering movement).
- Perform a wiggle test on the harness and connectors while monitoring bus activity to find intermittent faults.
- If wiring and bus voltages are good but no messages are present, test/replace the SAS or its CAN transceiver. If messages are present at the sensor but not at other modules, trace wiring to gateway/ABS/BCM.
- If a module replacement is performed, ensure correct coding/programming and perform required initialization/calibration of the SAS (steering angle calibration).
- After repair, clear codes and verify proper operation of SAS data on the CAN bus and restoration of related systems.
Likely causes
- Damaged or corroded SAS connector or pin(s)
- Open power or ground feed to the SAS
- Broken CAN_H or CAN_L conductor or poor splice/repair
- Failed CAN transceiver in the SAS or gateway module
- Missing/failed termination resistor or short across CAN lines
- Software/coding error after module replacement or update
Fault status
Status
No CAN communication with Steering Angle Sensor — SAS messages not received on CAN bus.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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