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B165511

B165511 is a BYD SRS (Supplemental Restraint System / airbag system) circuit diagnostic trouble code — Seal U

Safety System

B165511 is a BYD SRS (Supplemental Restraint System / airbag system) circuit diagnostic trouble code.

B1655 specifically designates the Left Front Frontal Impact Sensor circuit, and 11 is the subtype code indicating a Short to Ground.

This fault indicates the SRS control module detects an abnormally low-resistance path (typically less than 1 ohm) between the left front impact sensor signal circuit and vehicle body ground, preventing the control module from correctly receiving the sensor acceleration signal.

This fault forces the airbag system into fail-safe mode and continuously illuminates the instrument panel SRS warning light.

During a collision, this condition may prevent the left front airbag from deploying normally or delay its deployment.

This constitutes a severe fault affecting occupant safety.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

Reversed wiring harness colours after accident repairs caused DTC B165511

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A BYD Song had the airbag warning light stay on after collision repairs. A diagnostic scan revealed DTCs B165511 (Left frontal collision sensor short to ground) and B167011 (Right side collision sensor short to ground). The technician initially replaced both collision sensors, but the fault persisted. Further inspection found that the engine bay wiring harness had been replaced during the accident repair. The work did not strictly follow the wiring diagram, causing the wire colours for pins 1 and 2 of the left frontal collision sensor connector B02(A) to be reversed compared to the diagram (the actual wire colours were opposite). After swapping the pin connections, the fault codes cleared. This case shows that during accident repairs, always verify pin definitions against the wiring diagram rather than relying solely on wire colour memory.
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BYD DTC AI Analysis

Left front impact sensor connector shorted due to water ingress after wading

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A BYD Qin EV's SRS warning light came on after the vehicle drove through water during heavy rain. A scan tool retrieved DTC B165511. Inspection found water inside the impact sensor connector beneath the left front bumper; the pins had green oxide, causing a short to ground on the signal wire. The waterproof seal on the connector had aged, letting water in when driving through water. Thoroughly cleaned the connector pins with electronic cleaner, applied conductive grease, replaced the waterproof seal with a new one, and wrapped the connector with waterproof tape. Cleared the DTC and the system returned to normal. Advised the owner to regularly check the sealing condition of the wiring harness connectors inside the front bumper.
BYD DTC AI Analysis

Improper front bumper removal and refitting pinched and damaged the wiring harness.

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A BYD E2 had its front bumper replaced at a 4S dealership. After driving approximately 200 km, the airbag warning light illuminated. Retrieved DTC B165511. Inspection found that while installing the left front fender liner fixing screw, the technician trapped the left front impact sensor wiring harness under the screw. The screw threads pierced the harness insulation, allowing the copper core to contact the body metal and create a short to ground. Repair: Freed the trapped harness, wrapped the damaged area with electrical tape, rerouted the harness (ensuring at least 20 mm clearance from the fixing screw), added corrugated tubing for protection, and replaced the damaged harness section. Fault resolved.
BYD DTC AI Analysis

Internal short circuit in aftermarket crash sensor

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A BYD E3 displayed an airbag fault immediately after the left front impact sensor was replaced with a non-genuine part following a minor collision. The retrieved fault code was B165511. Checking the harness side of the sensor connector revealed no short to ground, and harness resistance was normal. Suspecting the new sensor, the technician removed it and measured internal resistance. The signal terminal to the housing (ground) showed 0.5 ohms, confirming an internal short in the aftermarket sensor. Replacing it with a genuine impact sensor resolved the fault. Impact sensors are part of the safety system and require genuine parts. Aftermarket components may have internal circuit design defects.
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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.