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PATS Transceiver Module Signal Is Not Received

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

Compare the reported angle with the real ride height:

  • BBody
  • 1Manufacturer-specific
  • 6Body
  • 81Sequence number

What does it mean?

B1681 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Rear Headlamp Leveling Sensor Circuit Performance .

Symptoms

  • Headlamp beams point too high or too low and do not correct when the vehicle is loaded
  • Oncoming drivers flash their lights because the beam is aimed too high
  • Headlamp system or adaptive lighting warning message in the cluster
  • The levelling motors do not perform their usual sweep at ignition on
  • Beam height jumps around while driving over uneven surfaces

Likely causes

  • Bent, disconnected or broken link rod between the sensor and the rear axle or suspension arm
  • Worn ball joints on the sensor linkage giving lost motion and an unstable signal
  • Corroded sensor body or a seized internal mechanism after years of exposure under the vehicle
  • Sensor bracket rusted, loose or bent after suspension work or an impact
  • Suspension modified, lowered or fitted with different springs so the sensor works outside its normal range
  • Calibration not carried out after suspension, headlamp or sensor replacement
  • Intermittent connection in the sensor connector caused by water and road salt

How to fix it

  1. Read the sensor value on live data with the vehicle unladen on a level floor, then load the rear of the vehicle and watch whether the value moves smoothly and in the right direction
  2. Inspect the sensor, the bracket and the link rod under the vehicle for corrosion, bending, missing clips and loose ball joints
  3. Move the linkage by hand through its full travel and watch the live value for dropouts or flat spots
  4. Check the connector for water and corrosion, and measure the reference voltage, ground and signal wire with the ignition on
  5. Wiggle the harness along the rear of the vehicle while watching the data to find an intermittent break
  6. Carry out the levelling system calibration after any repair, since the module needs a fresh reference position
  7. Replace the linkage first if it is worn, and the sensor only when it is proven to give an incorrect angle with sound wiring

Codes From the Same System

All Fault Codes

Related Similar Codes

This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.