AutoCodes – Generic – B1787

B1787 Code - Rear Occupant Classification Sensor Left Collision Detection

Quick Answer

The Diagnostic Trouble Code (DTC) B1787 is output when the Occupant Detection ECU receives a collision detection signal sent by the Rear Occupant Classification Sensor Left (LH) when an accident occurs. Common causes include Faulty Separate Type Rear Seat Cushion Spring Assembly Left (Rear Occupant Classification Sensor Left), Separate Type Rear Seat Cushion Spring Assembly Left harness is open or shorted, Separate Type Rear Seat Cushion Spring Assembly Left circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: B1787 indicates Rear Occupant Classification Sensor Left Collision Detection.
Common causes: Common causes include Faulty Separate Type Rear Seat Cushion Spring Assembly Left (Rear Occupant Classification Sensor Left), Separate Type Rear Seat Cushion Spring Assembly Left harness is open or shorted, Separate Type Rear Seat Cushion Spring Assembly Left circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 6,479

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Oct 16, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B1787 Description

The Diagnostic Trouble Code (DTC) B1787 is output when the Occupant Detection ECU receives a collision detection signal sent by the Rear Occupant Classification Sensor Left (LH) when an accident occurs. DTC B1787 is also stored when the separate type of front seat cushion spring assembly is subjected to a strong impact, even if an actual accident has not occurred. However, when the Occupant Detection ECU outputs a collision detection signal, even if the vehicle is not in a collision, DTC B1787 can be cleared by performing the zero point calibration and sensitivity check. Therefore, when DTC B1787 is output, first perform the zero point calibration and sensitivity check.

OBDII Code B1787 - Rear Occupant Classification Sensor Left Collision Detection - AutoCodes.com — B1787 Code - Rear Occupant Classification Sensor Left Collision Detection

What does this mean?

What are the Possible Causes of the DTC B1787?

Faulty Separate Type Rear Seat Cushion Spring Assembly Left (Rear Occupant Classification Sensor Left)
Separate Type Rear Seat Cushion Spring Assembly Left harness is open or shorted
Separate Type Rear Seat Cushion Spring Assembly Left circuit poor electrical connection
Faulty Occupant Detection ECU

How to Fix the DTC B1787?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B1787 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the B1787 code?

Need more information on how to fix the B1787 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B1787 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B1787 Lexus — Rear Occupant Classification Sensor Left Collision Detection
B1787 Scion — Rear Occupant Classification Sensor Left Collision Detection
B1787 Toyota — Rear Occupant Classification Sensor Left Collision Detection

Precautions for SRS “AIR BAG” and “SEAT BELT PRE-TENSIONER” Service

Never probe the electrical connectors on air bag, side air curtain modules or seat belts.
Never disassemble or tamper with safety belt buckle/retractor pretensioners, adaptive load limiting retractors, safety belt inflators, or probe the electrical connectors.
Do not use electrical test equipment to check SRS circuits unless instructed to in this Service Manual.
Before servicing the SRS, turn ignition switch OFF, disconnect both battery cables and wait at least 3 minutes. For approximately 3 minutes after the cables are removed, it is still possible for the air bag and seat belt pre-tensioner to deploy. Therefore, do not work on any SRS connectors or wires until at least 3 minutes have passed.

Failure to follow this instruction may result in the accidental deployment of these modules, which increases the risk of serious personal injury or death.

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about B1787 Code

1. What are common symptoms of OBDII code B1787 (Rear Occupant Classification Sensor Left Collision Detection)?

- Common symptoms include the airbag warning light illuminating on the dashboard and possible issues with the rear occupant classification system.

2. What could cause OBDII code B1787 to trigger?

- This code may be triggered by a fault in the rear occupant classification sensor on the left side, wiring issues, or damage to the sensor due to a collision.

3. How serious is OBDII code B1787?

- This code is related to the rear occupant classification system, which is crucial for proper airbag deployment in the event of a collision. It should be addressed promptly to ensure the safety features are functioning correctly.

4. Can I continue driving with OBDII code B1787 present?

- It is not recommended to ignore this code and continue driving, as it indicates a potential issue with the rear occupant classification sensor that could affect airbag deployment in case of an accident.

5. What are some repair tips for OBDII code B1787?

- Repair tips include checking and repairing any damaged wiring, inspecting and replacing the rear occupant classification sensor if necessary, and clearing the code to see if it returns.

6. How can I diagnose OBDII code B1787?

- Diagnosis involves using an OBDII scanner to retrieve the code, inspecting the rear occupant classification sensor and its wiring for damage, and testing the sensor's functionality.

7. Are there any recalls related to OBDII code B1787?

- It's advisable to check with the vehicle manufacturer or the National Highway Traffic Safety Administration (NHTSA) for any recalls related to the rear occupant classification system and this specific OBDII code.

8. Can a DIY enthusiast fix OBDII code B1787?

- Depending on your skill level and experience with automotive repairs, you may be able to address this code yourself by following repair guides and using the necessary tools to inspect and replace the rear occupant classification sensor.

9. How much does it cost to repair OBDII code B1787?

- The cost of repairing this code can vary depending on the extent of the damage, whether it requires sensor replacement, and if professional labor is needed. It's best to consult with a mechanic for an accurate estimate.

10. Will fixing OBDII code B1787 turn off the airbag warning light?

- Once the underlying issue triggering the code is repaired and the code is cleared, the airbag warning light should turn off. If it persists, further diagnosis may be required to ensure the system is functioning correctly.