B1773 – Rear right seat belt pretensioner not present (BYD)

B1773 means the rear right seat belt pretensioner circuit does not look “installed” to the vehicle. In real life, that usually turns the SRS/airbag warning on and can disable that seating position’s restraint functions. This is a manufacturer-specific BYD code, so the exact logic can vary by platform. According to BYD factory diagnostic data, this code indicates: Rear right seat belt pretensioner not present. Treat this as a safety-critical SRS fault. Depower and disable the SRS using OEM procedures before touching any related connector. Use only OEM-approved SRS test methods and a scan tool with full SRS access.

B1773 Quick Answer

On a 2020 BYD Dolphin, B1773 points to the SRS module not detecting the rear right seat belt pretensioner as present. Most often, the cause is an open circuit, a disconnected connector, or high resistance at the pretensioner connection, not an instantly “bad” pretensioner.

What Does B1773 Mean?

Official definition (BYD): “Rear right seat belt pretensioner not present.” The SRS system expects to see a valid pretensioner connected at the rear right seat belt. When the SRS module cannot confirm that device, it stores B1773 and commands the airbag warning status.

What the module checks and why it matters: The SRS control unit verifies the pretensioner circuit identity and electrical integrity. It does this with internal diagnostic checks on the squib loop and connector path. A missing connector, an open in wiring, or excess resistance can make the module interpret the pretensioner as “not present.” That distinction matters. The code points you to a suspected trouble area, not a condemned part, per SAE J2012-DA guidance.

Theory of Operation

Under normal conditions, the rear right pretensioner sits in the seat belt assembly and connects to the SRS harness through dedicated connectors. The SRS module continuously monitors each pretensioner circuit for plausibility. It looks for the expected electrical signature and circuit continuity using built-in diagnostics. The module then decides whether the circuit looks valid and ready.

With B1773, the SRS module does not see the expected signature for the rear right pretensioner. An unplugged connector can cause that quickly. Corrosion, terminal spread, or a harness pinch can also interrupt the circuit. Because this involves pyrotechnic components, you must disable the SRS before disturbing connectors. Avoid back-probing with standard test leads unless BYD service information permits it.

Symptoms

You will usually notice an SRS warning first, then scan-tool details during diagnosis.

• SRS warning Airbag/SRS indicator illuminated and stays on
• Message Safety restraint warning message on the cluster (if equipped)
• Code storage B1773 stored in the SRS control unit memory
• Readiness change Some SRS functions may show “not ready” or “fault” in scan data
• Rear seat coverage Reduced or disabled pretensioner function for the rear right position
• Intermittent behavior Warning may toggle with seat movement or temperature changes
• Post-repair event Code appears after rear seat, belt, or interior trim work

Common Causes

• Connector not fully seated at the pretensioner: A partially latched plug changes terminal contact and makes the SRS module interpret the device as missing.
• Rear right seat harness unplugged during interior work: Seat removal, trim work, or cleaning often leaves the pretensioner circuit disconnected.
• Open circuit in the pretensioner wiring: A broken conductor in the rear seat belt/pretensioner branch stops the module from seeing the expected load.
• High resistance from corrosion or moisture intrusion: Corroded terminals add resistance and can push the measured circuit value out of the “present” window.
• Terminal damage or poor pin fit: Spread terminals, bent pins, or a pushed-out terminal creates an intermittent “not present” result.
• Harness pinch or chafe near the seat frame or B-pillar trim: Seat movement and sharp edges damage SRS wiring and can open the circuit under load or vibration.
• Incorrect seat belt/pretensioner assembly installed: A mismatched BYD part or incorrect sub-harness can prevent the SRS module from recognizing the component.
• Aftermarket seat cover or accessory stressing the harness: Added tension on wiring can pull terminals or break conductors over time.
• SRS module coding/configuration mismatch after repairs: If the module configuration does not match installed equipment, it may flag the rear right pretensioner as not present.

Diagnosis Steps

Use a scan tool with full BYD SRS access, plus OEM service information for depowering steps and connector handling rules. Keep a DMM available for power and ground voltage-drop tests at the SRS module circuits only. Do not probe pretensioner connectors with standard test leads. Use only OEM-approved breakout methods and test adapters for SRS circuits.

1. Confirm DTC B1773 in the SRS/airbag system menu and record stored vs pending status. Save freeze frame data, if available, and note battery voltage, ignition state, and any companion SRS codes. Freeze frame shows when the fault set. A scan-tool snapshot helps catch an intermittent during a harness wiggle test.
2. Follow BYD depowering procedures before touching any SRS connector or seat belt pretensioner wiring. Disable the SRS system per OEM steps and wait the specified discharge time. Do not skip this step.
3. Check fuses and power distribution that feed the SRS module and related restraint circuits. Verify correct fuse fit and no heat damage at fuse blades. Inspect the power distribution path visually before meter work.
4. Verify SRS module power and ground integrity with voltage-drop testing under load. Command any available SRS self-test function that activates module loads, if supported. Measure ground drop during operation and keep it under 0.1V. High resistance can mimic missing components.
5. Re-enable the system as required for scan-tool communication checks, then perform a full network scan. Confirm the SRS module communicates normally and no low-voltage or network faults exist. Communication issues can create misleading “not present” messages.
6. Depower the SRS system again using BYD procedures. Remove trim as needed and inspect the rear right seat belt pretensioner connector area. Look for an unseated connector, secondary lock not engaged, water trails, corrosion, or pulled wiring at the strain relief.
7. Inspect the rear right pretensioner harness routing from the pretensioner toward the body harness. Focus on pinch points near the seat frame, lower anchor, and trim retainers. Check for chafing, crushed sections, or previous repair splices.
8. Check connector terminal condition and pin fit using OEM-approved methods only. Verify terminals have correct tension and sit flush in the housing. Repair pushed-out terminals and replace damaged connector bodies as needed.
9. Use the scan tool to view SRS data that relates to rear right pretensioner presence or circuit status, if the BYD software provides it. Compare the rear right reading to the rear left side when equipped similarly. A side-to-side comparison helps isolate wiring versus module logic issues.
10. If service information allows circuit testing, perform harness integrity checks using approved breakout adapters at the SRS module side, not at the pretensioner squib. Check for opens and high resistance across the harness path with the system depowered. Do not use continuity checks alone to “pass” a circuit. Confirm low resistance and stable readings while gently flexing the harness.
11. Correct the verified fault, then restore all connectors and locks. Re-enable the SRS system per BYD procedure and clear the DTC with the proper SRS scan tool function. Cycle ignition and recheck for immediate code return. A hard fault usually returns right away on key-on in a continuously monitored circuit.
12. Confirm the repair with a final full scan and a post-repair inspection of harness routing and clip retention. If the code returns, stop and recheck configuration and part correctness before replacing modules. Document findings and measurements.

Professional tip: Treat “pretensioner not present” as a circuit recognition fault first. BYD SRS logic expects a specific electrical load signature. A loose connector, poor pin tension, or high resistance often triggers this code with no visible damage. Always depower correctly and use OEM-approved SRS test adapters. Standard probes can spread terminals and create repeat comebacks.

Possible Fixes

• Reseat and lock the rear right pretensioner connector: Restore full engagement and confirm the secondary lock holds.
• Repair wiring damage in the rear right pretensioner branch: Fix opens, chafed insulation, or pinched sections using OEM-approved SRS wiring practices.
• Clean and restore terminal integrity: Address corrosion, replace damaged terminals, and correct poor pin fit that creates high resistance.
• Correct harness routing and retention: Reclip the harness away from seat frame pinch points and confirm slack for seat movement.
• Install the correct BYD pretensioner or sub-harness when mismatched: Verify part numbers and configuration match the vehicle equipment before installation.
• Configure or re-initialize the SRS system after verified hardware repair: Use the BYD-capable scan tool to complete any required setup when the vehicle equipment list changed.

Can I Still Drive With B1773?

You can usually drive a BYD Dolphin with B1773, but you should treat the SRS as compromised. This code means the vehicle does not see the rear right seat belt pretensioner as present. In a crash, that seat position may lose pretensioner function. The SRS warning lamp may also stay on, and some BYD platforms disable related restraint functions when any SRS fault sets. Do not attempt DIY SRS testing. Depower the SRS using OEM procedures before touching connectors, and avoid back-probing with standard test leads.

How Serious Is This Code?

B1773 is safety-critical, not a drivability code. The car may run normally, yet protection for the rear right occupant may drop. The module sets this fault when it cannot identify the pretensioner circuit as connected or plausible. That usually points to an open circuit, wrong component, connector issue, or harness damage. Treat the entire restraint system as potentially compromised until proven otherwise. Correct diagnosis requires an SRS-capable scan tool for BYD and OEM-approved test methods. Only trained, SRS-certified technicians should handle pretensioner and airbag circuit checks.

Common Misdiagnoses

Technicians often replace the rear right pretensioner because the description says “not present.” That wastes money when a loose under-seat connector or high resistance at a terminal causes the same symptom. Another common mistake involves using a standard multimeter on the squib circuit. That can damage components or create a deployment risk. Some shops also clear codes and release the car without checking SRS data, seat occupancy inputs, and connector fit. Use the scan tool to confirm the module reports the right seat position and pretensioner status, then verify wiring integrity with OEM-approved adapters.

Most Likely Fix

The most common confirmed repair direction involves restoring a solid connection at the rear right pretensioner connector or repairing an open in the rear seat belt pretensioner harness. Start with SRS depowering, then inspect for partially seated locks, spread terminals, corrosion, or harness strain near the seat base. After repairs, run a full SRS self-check with a BYD-capable scan tool and confirm the pretensioner now shows as present. Do not assume a new pretensioner will fix it until you prove the circuit fault.

Repair Costs

SRS/airbag repair costs vary significantly by component. Diagnosis must be performed by a qualified technician with SRS-capable equipment. Do not attempt airbag system repairs without proper training and safety procedures.

Last updated: March 29, 2026