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Acoustic Vehicle Alerting System (AVAS) Function and Wiring Details

Objective

To outline the function, wiring architecture, and electrical path for the Acoustic Vehicle Alerting System (AVAS). This guide assists technicians in verifying safety compliance and troubleshooting communication or power issues within the low-speed audible alert system.

The AVAS generates synthetic sound that varies in pitch and volume based on vehicle speed. This provides auditory cues for:

  • Pedestrian and cyclist safety.

  • Regulatory compliance.

  • Indicating vehicle behavior (acceleration, deceleration, and reversing).

Tools Required

  • Digital Multimeter (DMM)

  • Raptor (only if communication faults are present)

  • Vehicle-specific Wiring Schematics  365-2150 (Reference BOM 2536-24-3140)

  • Mounting Drawing (Reference 162-24-3139)

Vehicle Preparation

  1. Safety First: Ensure the vehicle is powered down and the high-voltage system is isolated if necessary, though these components operate on the 12V chassis side.

  2. Access: Locate the front and rear speaker mounting positions as identified in drawing 162-24-3139.

  3. Regulation Awareness: Note that the AVAS is mandated to operate at speeds below 19 mph (30 km/h) to alert pedestrians.

Procedure

Part 1: AVAS Front Speaker Wiring


The front speaker integrates into the cabin-side communication and power networks.

  1. CAN Bus Interface: The speaker connects to CAN2 in series at B15 (EVCC).

    • Harness Reference: 365-2150.

  2. Power Supply:

    • 12V (+) and (-): These wires are routed to the cab pass-throughs located on the exterior of the cab.

Part 2: AVAS Rear Speaker Wiring

The rear speaker is wired for chassis-side communication and direct battery power.

  1. CAN Bus Interface: The speaker connects to CAN2 in series at A23 (Drive Motor).

    • Harness Reference: 365-2151.

  2. Power Supply:

    • 12V (+) and (-): These wires connect directly to the battery terminals, bypassing cab pass-throughs.

Troubleshooting Guidelines

  • No Sound (Front or Rear): Verify 12V power at the respective source (cab pass-through for front, battery for rear).

  • Speed Sensing Issues: If the pitch does not change with speed, check the CAN2 data stream for valid vehicle speed signals from the VCU or Drive Motor.