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2019 XC60 T5 - BLIS / Cross Traffic Alert System Malfunction

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Mike T. · rep 0 · May 25, 3:55 AM · 1 replies · solved · Question

Vehicle: 2019 Volvo XC60 T5 Momentum

My 2019 Volvo XC60 T5 Momentum is consistently showing a "BLIS / Cross Traffic Alert System Malfunction" message on the dashboard. This started appearing intermittently a few weeks ago, but now it's constant every time I drive. Both sides of the system seem affected, and the blind spot monitoring lights in the mirrors never illuminate, nor does the cross-traffic alert work when backing up.

I've tried cleaning the rear bumper where the radar sensors are located, making sure there's no dirt or snow blocking them, but I've had no luck. Could this be a sensor issue, or is it something more complex like a wiring problem or a control module?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:55 AM

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ClearTheCode admin answer:

Blind Spot Information System (BLIS) and Cross Traffic Alert (CTA) malfunctions are common issues that can stem from various electrical or sensor-related problems. Given that both sides are affected and the message is constant, it suggests a systemic issue rather than just a single dirty sensor.

  1. Thorough Sensor Inspection: Even after cleaning, visually inspect the BLIS radar sensors (located inside the rear bumper corners, usually behind the bumper cover) for any physical damage, cracks, or signs of impact. Sometimes, even minor bumper impacts can dislodge or damage the delicate sensors.
  2. Wiring Harness Check: The wiring harness connecting the BLIS sensors to the vehicle's electrical system can be susceptible to damage from road debris, moisture, or even rodent activity. A technician would inspect the harness for cuts, corrosion, or loose connections.
  3. Diagnostic Trouble Codes (DTCs): A professional scan tool (like Volvo's VIDA) can read specific fault codes related to the BLIS system. Common codes include:
    • B1A00: BLIS Sensor Fault (generic sensor fault)
    • B1A01: Left BLIS Sensor Communication Fault
    • B1A02: Right BLIS Sensor Communication Fault
    • U0155: Lost Communication with Instrument Panel Cluster Control Module (could affect BLIS display) These codes will pinpoint which sensor or communication line is failing.
  4. Sensor Calibration: After replacement or sometimes even after a software update, BLIS sensors require calibration to ensure they accurately detect objects. This is a dealer-level procedure.
  5. Module Failure: Less commonly, the BLIS control module itself (often integrated into the sensors or a separate module) can fail.

Causes:

  • Damaged or faulty BLIS radar sensors (most common).
  • Corroded or damaged wiring harness to the sensors.
  • Software glitch requiring an update or reset.
  • Interference from aftermarket accessories (rare).
  • Control module failure.

When to See a Shop: Since you've already cleaned the sensors and the issue is persistent, it's highly recommended to take your XC60 to a Volvo dealership or a specialized independent shop. They have the necessary diagnostic equipment to read specific BLIS fault codes, test sensor functionality, inspect wiring, and perform any required sensor replacements and calibrations. Attempting to replace sensors without proper calibration can lead to continued malfunction.

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