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2020 QX80 Rear Air Suspension Sagging Overnight

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Rachel A. · rep 0 · May 22, 5:10 AM · 1 replies · solved · Question

Vehicle: 2020 Infiniti QX80 Sensory

Hello forum,

I've got a 2020 Infiniti QX80 with the Hydraulic Body Motion Control (HBMC) system, and I've noticed a concerning issue. When the car sits overnight, especially in colder weather, the rear end sags significantly. It usually levels out once I start driving, but it looks really odd when parked.

Is this a common problem with the QX80's air suspension or HBMC system? What could be causing this? I'm worried about potential leaks or compressor issues. Any advice on what to check or if there are any known TSBs for this model year would be great. Thanks!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:10 AM

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ClearTheCode admin answer:

Sagging rear suspension in a 2020 Infiniti QX80, particularly after sitting overnight, is a classic symptom of an issue within the self-leveling or Hydraulic Body Motion Control (HBMC) system. While the QX80 uses a hydraulic system rather than traditional air springs for HBMC, similar principles of pressure loss can apply.

  1. Visual Inspection for Leaks: Carefully inspect the hydraulic lines, connections, and shock absorbers for any visible signs of fluid leaks. Even a small leak can lead to pressure loss over time.
  2. Listen for Compressor/Pump Operation: When you start the vehicle, listen for the sound of the HBMC pump engaging to re-level the vehicle. If it's excessively loud, runs for a long time, or doesn't seem to engage, it could indicate a pump issue.
  3. Check for Obstructions: Ensure there are no obstructions or debris around the height sensors that might be providing incorrect readings to the control module.
  4. Review Maintenance History: Ensure the HBMC fluid has been checked or serviced according to Infiniti's recommendations. Low or contaminated fluid can impact system performance.

Common Causes:

  • Leaking Hydraulic Lines or Shocks: The most common cause of sagging is a leak in the hydraulic system, allowing fluid pressure to drop when the vehicle is off.
  • Faulty Height Sensors: If a height sensor is malfunctioning, it might incorrectly report the vehicle's height, leading the system to lower the rear end.
  • HBMC Pump/Accumulator Issues: The pump or pressure accumulator might not be maintaining adequate pressure, or the pump itself could be failing.
  • Control Module Malfunction: Less common, but the HBMC control module could be sending incorrect commands.

When to See a Shop: If you observe persistent sagging, hear unusual noises from the suspension area, or if the vehicle's ride quality deteriorates, it's imperative to take your QX80 to an Infiniti dealership or a specialized repair shop. They can perform a comprehensive diagnostic scan for relevant fault codes (e.g., C1101, C1102 related to HBMC system) and conduct pressure tests to pinpoint the exact source of the leak or malfunction within the complex HBMC system. Addressing these issues promptly can prevent further damage to components and ensure safe vehicle operation.

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