2025-2026 Lexus UX300h Collision Avoidance Module: RCTA, Programming, and Replacement Guide
This guide covers the essential details for diagnosing, replacing, and programming the collision avoidance module, with a critical focus on software calibration and option compatibility.
- Replacement is NOT plug-and-play; mandatory software calibration using dealer-level tools (Toyota Techstream) is required.
- Before buying, verify your vehicle has the Rear Cross Traffic Alert (RCTA) feature and that the part number is exactly 89340-76290.
- A "BSM Malfunction" warning does not always mean the module is bad; TSBs for similar models show a software update can often fix the issue.
- Due to the need for expensive, specialized calibration tools, this repair is not feasible for DIY mechanics and should be handled by a Lexus dealer or a qualified specialty shop.
Symptoms of a Failing Collision Avoidance Control Module
When the collision avoidance control module or its related sensors fail, the vehicle will typically display clear warnings on the dashboard. You will not lose the ability to drive the car, but key safety features will be disabled.
- "Check Blind Spot Monitor System" Message: The most common symptom is a warning message appearing on the Multi-Information Display (MID) located in the instrument cluster.
- BSM and RCTA Inoperative: The systems will not function. The indicator lights in the side mirrors will not illuminate when a vehicle is in your blind spot, and you will receive no alerts when backing out of a parking space.
- Illuminated Warning Light: A general malfunction or driving assist warning indicator may light up on the dashboard.
Associated OBD-II Diagnostic Trouble Codes (DTCs)
A professional scan tool is required to read these codes. Their presence strongly suggests a problem within the BSM system, though it could be the module, a sensor, the mirror indicator, or wiring.
- C1AB4 - Open in Outer Mirror Indicator (Module "B" Side / Master): This code points to an open circuit related to the passenger side (Master) mirror indicator.
- C1AB5 - Open in Outer Mirror Indicator (Module "A" Side / Slave): This code indicates an open circuit related to the driver side (Slave) mirror indicator.
- C1AB2 / C1AB3: These codes indicate a short to ground in the master or slave mirror indicator circuits, respectively.
Pro Tip: Technical Service Bulletins (TSBs) for other recent Lexus models show that these DTCs and a "BSM Malfunction" message can sometimes be resolved with a simple software update at the dealership, without replacing any parts. This should be considered as a first diagnostic step before condemning the module.
Known Issues, Recalls, and Technical Service Bulletins (TSBs)
As the 2025-2026 UX300h is a relatively new model, long-term failure patterns have not yet emerged. However, several official communications are relevant.
Recalls
While no recalls exist specifically for the collision avoidance module as of mid-2026, several recalls have been issued for the 2025 UX300h that owners should be aware of:
- NHTSA Recall 24V-587: Affects 141 vehicles built between January 9-17, 2024. A main engine room wire harness may fracture, leading to a sudden loss of driving power. The fix is a harness replacement by a dealer.
- NHTSA Recall 26V341: Affects a broader range of 2025 Lexus UX Hybrid vehicles. The instrument panel may fail to display certain warnings. The remedy is a software update performed by a dealer.
- NHTSA Noncompliance Recall 25V-744: The rear-view camera image may freeze. This is corrected by a software update to the Parking Assist ECU.
Programming and Calibration: A Job for the Pros
Warning: Replacing this module is not a simple plug-and-play repair. The new module MUST be calibrated to the vehicle for the system to function correctly and safely.
This is the most critical aspect of replacing the collision avoidance module or its sensors. Failure to perform the correct calibration will result in a non-functional system and persistent warnings on the dash.
- Dealer-Level Software Required: Calibration requires Toyota/Lexus's official diagnostic software, called Techstream. While some high-end aftermarket scan tools may offer this function, their coverage can be incomplete for the newest models, making the official Techstream software the only guaranteed method.
- Calibration Events: According to I-CAR, calibration is required any time the sensor (module) is removed, installed, or replaced, or if the mounting area on the body has been damaged or repaired.
- DIY Unrealistic: Access to Techstream software is expensive. A professional subscription costs $80 for two days or $1,500 for a year, and the required interface hardware costs over $1,600. This cost and complexity make DIY replacement and calibration impractical for most owners.
- Post-Repair Test Drive: After calibration, a test drive is necessary to confirm the system is operating correctly. The system can detect misalignment and trigger a warning after driving only a short distance, even if no fault codes were stored.
Buying a Used Collision Avoidance Control Module
Purchasing a used OEM module can offer significant savings over a new part. However, careful verification is essential to ensure you get the right part and avoid installation headaches.
Compatibility Check
The single most important factor is ensuring the module matches your vehicle's options.
- Verify Part Number: The correct part number for a 2025-2026 UX300h equipped with Rear Cross Traffic Alert (RCTA) is 89340-76290.
- Confirm RCTA Feature: The initial prompt noted a different module is used for vehicles without RCTA. While all 2025 and 2026 UX300h models sold in North America appear to come standard with RCTA, it is still wise to confirm. Do not purchase a module with a different part number, such as 89340-76270, which is for vehicles *without* this feature.
Physical Inspection
When the part arrives, inspect it carefully before installation.
- Check for Corrosion: Examine the electrical connector pins for any signs of green or white corrosion, which indicates water damage. A water-damaged module is likely to fail.
- Inspect the Casing: Look for cracks, deep scratches, or any signs that the plastic case has been pried open. This could indicate a failed repair attempt.
- Verify Connectors: Ensure the connector housings are intact and not cracked or broken.
Cost Breakdown
Prices can vary based on your location and the chosen repair shop. The primary costs are the part itself and the labor for installation and calibration.
| Part/Service | Estimated Cost |
|---|---|
| New OEM Module (89340-76290) | $300 - $450 |
| Used OEM Module | $100 - $250 (when available) |
| Shop Labor (Installation & Calibration) | $250 - $500 |
Note: Labor costs are based on 1.5-2.5 hours of work at a typical independent shop rate. Dealer rates may be higher. Calibration by a specialist may be a separate charge. New OEM price is estimated based on similar parts.
Frequently Asked Questions (FAQ)
Do I have to go to a Lexus dealer for this repair?
Not necessarily, but it is highly recommended. While a well-equipped independent shop that specializes in Toyota/Lexus and owns the proper Techstream software can perform the replacement and calibration, many shops do not have this capability. A Lexus dealer guarantees access to the correct tools and latest software updates. Always ask an independent shop specifically if they can calibrate a new BSM module on a late-model Lexus before authorizing work.
Where is the collision avoidance module located?
The UX300h uses two radar sensor modules that make up the system. They are located in the rear corners of the vehicle, behind the plastic bumper cover. The passenger side module is considered the "Master" and the driver side is the "Slave".
Can a bad collision avoidance module drain my car's battery?
It is possible, but not common. A faulty electronic module can sometimes fail to shut down correctly when the car is turned off, leading to a parasitic battery drain. However, the more likely symptoms are the warning messages and loss of BSM/RCTA functionality.
Will replacing the module guarantee a fix for my "BSM Malfunction" warning?
Not always. The warning can also be caused by a faulty radar sensor, a bad indicator light in one of the side mirrors, or a problem in the wiring harness connecting them. Furthermore, as noted in TSBs for similar models, the issue could be purely software-related and fixable with a reflash by the dealer. Proper diagnosis is key before replacing expensive parts.
Technical Specifications
OEM Part Numbers: 89340-76290
Manages Blind Spot Monitor (BSM) and Rear Cross Traffic Alert (RCTA) systems. Requires post-installation calibration with Toyota Techstream software.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Lexus UX300h:
- 🛍️ Shop This Part
- Symptoms of a Failing Collision Avoidance Control Module
- Associated OBD-II Diagnostic Trouble Codes (DTCs)
- Known Issues, Recalls, and Technical Service Bulletins (TSBs)
- Recalls
- Programming and Calibration: A Job for the Pros
- Buying a Used Collision Avoidance Control Module
- Compatibility Check
- Physical Inspection
- Cost Breakdown
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off