C2 CHECK THE SPEED COMPENSATED VOLUME SETTING

Yes	GO to C2
No	REFER to: Instrumentation, Message Center and Warning Chimes (413-01 Instrumentation, Message Center and Warning Chimes) . See Symptom Chart: Instrument Panel Cluster (IPC): The speedometer is inoperative

Turn the speed compensated volume off. Refer to the Owner's Literature. Operate the audio system in AM/ FM mode. Drive the vehicle at various speeds and observe the speaker volume. Set the speed compensated volume to maximum compensation. Refer to the Owner's Literature. Operate the audio system in AM/ FM mode. Drive the vehicle at various speeds and observe the speaker volume.

Does the volume remain constant with the speed compensated volume turned off, and increase and decrease with vehicle speed with the speed compensated volume set to maximum?

Yes	The system is operating correctly at this time. INSTRUCT the customer in the correct usage of the speed compensated volume feature.
No	GO to C3

C3 CHECK FOR DTC (DIAGNOSTIC TROUBLE CODE) U0155:00

Using a diagnostic scan tool, retrieve all Continuous Memory Diagnostic Trouble Codes (CMDTCs).

Is DTC U0155:00 retrieved in any audio system module?

Yes	GO to Pinpoint Test AI
No	GO to C4

C4 CHECK FOR CORRECT ACM (AUDIO FRONT CONTROL MODULE) OPERATION

Ignition OFF. Disconnect and inspect all the ACM connectors. Repair:

Corrosion (clean module pins or install new connectors or terminals) Damaged or bent pins (install new terminals or pins) Pushed-out pins (install new pins as necessary)

Reconnect the ACM connectors. Make sure they seat and latch correctly. Operate the system and determine if the concern is still present.

Is the concern still present?

Yes	CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new ACM. REFER to: Audio Front Control Module (ACM) (415-00A Information and Entertainment System - General Information - Vehicles With: AM/FM/CD/SYNC, Removal and Installation).
No	The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.

Yes

CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new ACM. REFER to: Audio Front Control Module (ACM) (415-00A Information and Entertainment System - General Information - Vehicles With: AM/FM/CD/SYNC, Removal and Installation).

The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.

Source reference 4138

2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.