Test Y: The Speed Sensitive Volume Does Not Operate Correctly

PINPOINT TEST Y: THE SPEED SENSITIVE VOLUME DOES NOT OPERATE CORRECTLY

Normal Operation
The speed sensitive volume function adjusts the volume based on the vehicle speed sensor (VSS) signal from the instrument cluster (IC). The IC does not generate the VSS signal; it gateways the signal from the PCM.

For vehicles without THX(R) sound, the audio control module (ACM) receives the VSS signal from the IC. For vehicles with THX(R) sound, the audio digital signal processing (DSP) module receives the VSS signal from the IC and controls the speed sensitive volume based on the ACM setting.

- DTC U0155 (Lost Communication With Instrument Panel Cluster Control Module) - sets when the VSS signal is lost for greater than 5 seconds. When the signal is lost, the ACM turns the speed sensitive volume feature off. The smart junction box (SJB) and HVAC module also receive this signal, and should demonstrate symptoms if the VSS signal is lost. If no symptoms are present, this DTC can be ignored, as it may have been set by a low battery voltage condition.
- DTC U0184 (Lost Communication With Radio [ACM]) - set by the DSP module when expected medium speed controller area network (MS-CAN) messages are missing from the ACM lost for greater than 5 seconds. This includes the speed sensitive volume setting. If the speed sensitive volume setting message is missing, the DSP module turns the speed sensitive volume feature off.

This pinpoint test is intended to diagnose the following:
- Speed sensitive volume setting
- VSS signal concern
- ACM

Y1-Y3:

Y4-Y6: