Is a fluctuating AC voltage present each time the VOICE steering wheel switch is operated?

Positive Lead	Measurement / Action	Negative Lead
C240B-8		C240B-21

415-00A General Information -Vehicles With AM-FM-CD-SYNC — original illustration 1, reference 4179Original colors & callouts · Select to enlarge

Yes	GO to R9
No	GO to R4

R4 CHECK THE APIM (SYNC MODULE) MONO OUTPUT CIRCUITS TO THE ACM (AUDIO FRONT CONTROL MODULE) FOR A SHORT TO VOLTAGE

Ignition OFF. Disconnect: ACM C240B. Disconnect: APIM C2383. Ignition ON. Measure:

Click to display connectors

Positive Lead	Measurement / Action	Negative Lead
C240B-8		Ground
C240B-21		Ground

Is any voltage present?

Yes	REPAIR the circuit in question.
No	GO to R5

R5 CHECK THE APIM (SYNC MODULE) MONO OUTPUT CIRCUITS TO THE ACM (AUDIO FRONT CONTROL MODULE) FOR A SHORT TO GROUND

Ignition OFF. Measure:

Click to display connectors

Positive Lead	Measurement / Action	Negative Lead
C240B-8		Ground
C240B-21		Ground

Are the resistances greater than 10,000 ohms?

Yes	GO to R6
No	REPAIR the circuit in question.

Source reference 4179

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.