Pinpoint Test D: The Audio System Illumination Is Inoperative
WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
Refer to appropriate SYSTEM WIRING DIAGRAMS article, Cluster and Panel Illumination for schematic and connector information.
Normal Operation
With the parking lamps on, the lighting control module (LCM) supplies a variable pulse width modulated (PWM) voltage to the audio unit on circuit 484 (OG/BK). The base audio unit illumination is grounded through circuit 57 (BK). The dual media audio unit is grounded through circuit 694 (BK/LG).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Audio unit
PINPOINT TEST D: THE AUDIO SYSTEM ILLUMINATION IS INOPERATIVE
NOTE:
Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
- D1 CHECK CIRCUIT 484 (OG/BK) FOR AN OPEN
- Disconnect: Audio Unit C290a or C240
- With the parking lamps on, rotate the instrument panel dimmer switch to the maximum brightness position.
- Measure the voltage between the audio unit C290a-3, circuit 484 (OG/BK), harness side and ground; or between the audio unit C240-1, circuit 484 (OG/BK), harness side and ground.
- Is the voltage greater than 10 volts?
- YES : Go to D2.
- NO : REPAIR the circuit in question. TEST the system for normal operation.
- D2 CHECK CIRCUIT 57 (BK) OR 694 (BK/LG) FOR AN OPEN
- Measure the resistance between the audio unit C290a-13, circuit 694 (BK/LG), harness side and ground; or between the audio unit C240-2, circuit 57 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
- YES : REMOVE the audio unit. REFER to INFORMATION & ENTERTAINMENT SYSTEMS article. SEND it to an authorized audio system repair facility. TEST the system for normal operation after repair.
- NO : REPAIR the circuit in question. TEST the system for normal operation.