AU
C046008

DTC C046008 indicates an unreliable or incorrect SAS (Steering Angle Sensor) signal value in the EPS (Electric Power Steering) system 0x11F message — Seal U

Braking System

DTC C046008 indicates an unreliable or incorrect SAS (Steering Angle Sensor) signal value in the EPS (Electric Power Steering) system 0x11F message.

Although originally classified under the ABS/braking system, modern vehicle architectures route the SAS signal via the CAN bus to both the ESP (Electronic Stability Program) and the EPS.

The control unit sets this fault when it detects the steering angle sensor signal exceeds the plausible range, exhibits abnormal jumps, experiences a sampling timeout, or fails the logical correlation check with the wheel speed sensor signals (as related code C052801 indicates).

This fault limits ESP functionality, causes abnormal steering assistance, or disables the automatic emergency braking system, severely impacting driving stability.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Steering Angle Sensor (SAS) internal damage or signal drift, commonly caused by mechanical impact to the sensor during a front-end collision.
  • 2Poor contact, open circuit, or short circuit in the steering wheel clock spring or SAS wiring harness connector interrupts signal transmission.
  • 3Failure to perform SAS zero-point calibration and maximum steering angle learning using the dedicated diagnostic tool after replacing the steering gear, steering column, or performing chassis repairs.
  • 4Abnormal wheel speed sensor signal (e.g., single wheel speed deviation or incorrect sensor installation direction) causes the EPS/ABS control unit to judge the SAS signal as unreliable during cross-validation.
  • 5Outdated EPS control unit software version or control unit hardware internal AD sampling circuit fault.
What To Do
  • 1
    Pre-inspection and data collection: Check battery voltage (≥12V), verify the status of all instrument cluster warning lights, read all DTCs and freeze frame data using a diagnostic tool, and check for related fault codes such as C052801 (SAS and wheel speed check abnormal).
  • 2
    Physical inspection: Check the steering wheel clock spring connector for looseness, verify correct SAS sensor installation (especially on accident-repaired vehicles), and inspect the related wiring harness for pinching, damage, or corrosion.
  • 3
    Signal verification: Access the EPS data stream and observe the actual SAS angle value. Slowly turn the steering wheel from lock to lock. Verify the angle changes linearly without jumps and reads within 0°±5° when the steering wheel is straight ahead.
  • 4
    Wheel speed signal cross-check: Read data from the four wheel speed sensors. While driving the vehicle or rotating the wheels on a lift, confirm all wheel speed signals are consistent and show no jumps to rule out wheel speed differences causing the system to judge the SAS signal as unreliable.
  • 5
    Sensor calibration: Use a BYD dedicated diagnostic tool (such as VDS or ED400) to perform the 'Steering Angle Sensor Calibration' procedure, including zero position calibration and maximum steering angle learning. Clear the fault code after completion.
  • 6
    Control unit check: If the fault persists after calibration, check the EPS control unit power supply and ground. If necessary, update the EPS control unit software or replace the EPS assembly.
  • 7
    Final verification: Clear all DTCs and perform a road test (including straight-line driving, left and right turns, and stationary steering). Confirm the fault code does not recur and the ESP/ABS warning light turns off.
Real-World Cases
BYD DTC AI Analysis

BYD S7 ESP warning light on after front-right accident

✓
Symptoms: After a right-front collision, the ESP warning light stayed on. Fault code: C046008 (SAS signal fault). Diagnosis: Technicians found the steering rack had been removed and reinstalled during accident repairs, possibly shifting the steering angle sensor position. Live data showed the steering angle at 15° with the wheel straight (outside ±5° spec). Resolution: They rechecked the sensor mounting, used a dedicated diagnostic tool to run steering angle sensor zero calibration and max angle learning, cleared the codes, and test drove the vehicle. The ESP light went out; fault resolved.
Original source ↗
BYD DTC AI Analysis

Autohome Forum: C046008 DTC Circuit Troubleshooting Case

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Symptoms: Vehicle had no accident history, but the ABS/ESC warning lights intermittently illuminated on the instrument cluster. Scan tool retrieved DTC C046008. Diagnosis: The fault code indicated an unreliable SAS signal. The technician inspected the wiring harness connector between the EPS control unit and the SAS, finding a loose connection at the clock spring connector below the steering wheel. Continuity testing showed an intermittent open circuit in the SAS signal line. Resolution: Reconnected the clock spring connector and applied conductive grease to prevent oxidation. Secured the wiring harness with cable ties to prevent strain when turning the steering wheel. Cleared the fault codes and monitored for one week without recurrence.
Original source ↗
BYD DTC AI Analysis

BYD Seal 06 DM-i Official Diagnostic Manual Case

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Symptoms: Instrument cluster displayed "Check ESP System" with intermittent heavy steering. Scan tool read C046008 (EPS 0x11F message: SAS signal value unreliable/faulty). Some vehicles also log C052801 (SAS signal vs wheel speed check abnormal). Diagnosis: Per the workshop manual, checked live data for all four wheel speed sensors. Right-rear wheel speed signal fluctuated intermittently. Found the right-rear wheel speed sensor was not fully pushed in during installation, leaving excessive air gap to the tone ring. Fix: Reinstalled the right-rear wheel speed sensor to the standard position. Cleared fault codes; SAS and wheel speed signal cross-check passed and C046008 disappeared.
Original source ↗
BYD DTC AI Analysis

General Steering Angle Sensor System Diagnostic Procedure (Compatible with BYD EPS Architecture)

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Symptoms: Steering wheel position sensor primary and secondary signal fault; angle signal sampling timeout. Diagnosis: Performed standard EPS diagnostics. Checked battery voltage (10.8V, low) and EPS control unit power circuit. Connected scan tool, cleared DTCs, and test drove at safe speed while turning the steering wheel repeatedly. Fault returned. Removed the steering angle sensor and found internal photoelectric components contaminated. Solution: Replaced steering angle sensor assembly with same model; performed zero-point calibration and maximum steering angle learning. Also replaced aging battery to stabilize voltage. Fault eliminated.
Original source ↗
BYD DTC AI Analysis

C046008 Fault Code Power and Ground Troubleshooting Case

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Symptoms: Intermittent C046008 after startup, with communication faults across multiple control units. Diagnosis: Suspected power supply fault. Battery voltage fluctuated between 11–13 V at idle; alternator output unstable. Found EPS control unit ground bolt oxidised and loose. Resolution: Cleaned and tightened the EPS control unit ground. Replaced the faulty alternator regulator. Stabilised system voltage to 13.5–14.5 V. Cleared fault codes; C046008 has not returned. Confirmed unstable supply voltage causes SAS signal sampling faults.
Original source ↗
Other Seal U Fault Codes
B1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.