2017 Volvo S90 & V90 Blind Spot (BLIS) Module Failure: Diagnosis and Replacement
This guide covers the common failures, part numbers, and critical programming requirements for the blind spot radar modules on the 2017 Volvo S90 and V90.
- A used BLIS module is NOT plug-and-play and requires mandatory programming and calibration by a Volvo dealer or specialist with VIDA software.
- The modules are side-specific. The right (passenger) side is part #31665693 and the left (driver) side is #31665692.
- Failure is often caused by minor rear-end impacts or water intrusion into the electrical connector, due to their location behind the bumper cover.
- A "BLIS Service Required" message is the most common symptom, which also disables the Cross Traffic Alert (CTA) function.
Symptoms of a Failing BLIS Module
When a blind spot module on your 2017 Volvo S90 or V90 begins to fail, you will typically see a clear warning message on the dashboard. Here are the most common symptoms:
- "BLIS Service Required" Message: This is the most direct indicator of a fault within the system. The car's diagnostic system has detected a problem with one or both of the radar modules or their communication.
- Warning Light Malfunction: The orange warning light in the side mirror may behave erratically. It might stay illuminated constantly, flicker, or not light up at all, even when a car is in your blind spot.
- Constant False Alerts: The system may trigger warnings when there are no vehicles nearby. This can be caused by an internal module fault or misalignment.
- No Alerts at All: The most dangerous symptom is a complete lack of warnings, which means a key safety feature is inactive.
- Cross Traffic Alert (CTA) Unavailable: Since the same radar modules power both BLIS and CTA, you will likely lose both functions simultaneously.
Known Issues and Causes of Failure
These modules are located in a vulnerable position and are susceptible to several common issues.
Physical Damage and Misalignment
The modules are mounted in brackets behind the rear bumper cover, one on each corner. Even a minor parking lot bump or backing into a small obstacle can be enough to damage the module, break its mounting bracket, or knock it out of its precise alignment. A misaligned sensor will not read the environment correctly and will trigger a system fault.
Water Intrusion and Corrosion
Their location in the bumper area makes the modules and their electrical connectors highly susceptible to water, road salt, and grime. Over time, moisture can penetrate the connector seals, causing corrosion on the pins and leading to intermittent or total loss of communication. A Volvo Technical Journal (TJ 25788.1.3) specifically notes that checking connections for corrosion is a key diagnostic step.
Software Faults
In some cases, the "BLIS Service Required" message can be triggered by a software bug. A Volvo dealer or a specialized independent shop with VIDA diagnostic software can check if any software updates are available for the modules before condemning the hardware.
Pro Tip: Before assuming the module has failed, thoroughly wash the rear bumper, specifically the corner areas. A buildup of dirt, snow, or ice can block the radar's view and cause a temporary "BLIS unavailable" message. If the system works correctly after cleaning, you've saved yourself a trip to the mechanic.
Buying a Used Blind Spot Module for S90 & V90
Given the high cost of new OEM modules, a used part can be a cost-effective solution. However, there are critical factors to consider before you buy.
Warning: A used BLIS module is NOT plug-and-play. These modules are part of the vehicle's integrated safety system and are paired to the car's central computer. After installation, a used module must be calibrated and programmed to your vehicle using Volvo's official diagnostic software (VIDA). This procedure can only be done by a Volvo dealership or a well-equipped independent specialist. Failure to program the module will result in it not functioning and the "BLIS Service Required" error remaining.
What to Check Before Buying:
- Verify the Part Number: These modules are side-specific. Ensure you are buying the correct one for the driver (left) or passenger (right) side. The most current part number supersedes older ones. It's best to match the latest number.
- Inspect the Connector: Ask for clear photos of the electrical connector pins. Look for any signs of green or white corrosion, bent pins, or damage to the plastic housing. Do not buy a module with a corroded connector.
- Check for Physical Damage: Examine the casing for cracks, deep scuffs, or broken mounting tabs. Any sign of impact damage suggests the delicate radar inside could be compromised.
- Source from a Reputable Recycler: Purchase from a seller who offers a warranty. This gives you protection in case the module is faulty, as you won't know for sure until you attempt to have it programmed.
Cost Comparison for BLIS Module Replacement
The cost can vary significantly between new and used parts, but remember to factor in the mandatory programming for a used module.
| Part/Service | Estimated Cost | Notes |
|---|---|---|
| New OEM Module | $810 - $1,050 | Price for a single module from a Volvo dealership. |
| Used OEM Module | $95 - $250 | Price from online recyclers and eBay. Varies based on condition and availability. |
| New Aftermarket | Not Available | Direct-fit aftermarket replacements for the OEM system are not commonly available. Universal kits exist but are not a suitable repair. |
| Shop Labor (Replacement) | $150 - $400 | Estimated 1-2 hours to remove the rear bumper and swap the module. |
| Shop Labor (Programming/Calibration) | $150 - $300 | This is a separate, mandatory step for a used module, performed by a dealer or specialist. |
Replacement Overview & Difficulty
Replacing the BLIS module is a moderately difficult job due to the need for bumper removal and the absolute requirement for post-installation programming.
- Difficulty Rating: 4 out of 5
- Procedure: The process involves removing the rear tail lights, numerous screws in the wheel wells and underside, and carefully unsnapping the bumper cover from its clips. The module itself is then unbolted from its bracket behind the bumper.
- DIY Feasibility: While a skilled DIY mechanic can physically swap the part, the final programming step makes this a poor candidate for a complete home repair. You will still need to take the car to a shop for calibration.
Part Numbers and Compatibility
These modules are side-specific. Always verify the part number on your original unit before ordering a replacement.
| Position | Latest OEM Part Number | Supersedes Older Part Numbers |
|---|---|---|
| Right (Passenger Side) | 31665693 | 31687390, 31499940, 31476725, 31476331, 31451934, 31451214, 31387149 |
| Left (Driver Side) | 31665692 | 31687389, 31499939, 31476724, 31476330, 31451933, 31451213, 31360336 |
These parts also fit other Volvo models on the same platform, including the 2016-2019 XC90 and 2018-2021 XC60.
Frequently Asked Questions (FAQ)
Does a used BLIS module need to be programmed?
Yes, absolutely. The BLIS module is a safety component that is electronically paired to the vehicle. A used module must be calibrated and programmed with Volvo's VIDA software to communicate with your car. Without this step, it will not work.
Can I replace the blind spot module myself?
Physically replacing the module is possible for an experienced DIYer, as it involves removing the rear bumper cover and unbolting the part. However, because professional programming is required for the part to function, you cannot complete the entire job at home. You will save on the physical installation labor but must still budget for a trip to a dealer or specialist.
Why did my blind spot sensor fail after a minor accident?
The sensors are extremely sensitive to impact and alignment. Even a minor bump that doesn't visibly damage the bumper cover can be enough to crack the sensor's internal components, break its mounting bracket, or throw off its precise calibration, causing the system to report a fault.
Is there a recall for the BLIS system on the 2017 S90 or V90?
No, there are no specific recalls for the failure of the BLIS radar modules. There was a Technical Journal (TJ 25788.1.3) issued to help technicians diagnose fault messages, which could be caused by software or connection issues. Other recalls for 2017 models concerned different components like airbag bolts and GPS software.
Technical Specifications
OEM Part Numbers: 31665693 31687390 31665692 31687389
Radar-based sensor module for Blind Spot Information System (BLIS) and Cross Traffic Alert (CTA).
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.
- Volvo V90:
- Volvo S90:
- 🛍️ Shop This Part
- Symptoms of a Failing BLIS Module
- Known Issues and Causes of Failure
- Physical Damage and Misalignment
- Water Intrusion and Corrosion
- Software Faults
- Buying a Used Blind Spot Module for S90 & V90
- What to Check Before Buying:
- Cost Comparison for BLIS Module Replacement
- Replacement Overview & Difficulty
- Part Numbers and Compatibility
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off