Pinpoint Test E: Poor Quality/Distorted/No Sound From All Speakers
Information and Entertainment System
Pinpoint Test E: Poor Quality/Distorted/No Sound From All Speakers
Normal Operation
The audio Digital Signal Processing (DSP) module is enabled by a enable/clip circuit. To enable the audio DSP (Digital Signal Processing) module, the Audio Control Module (ACM) sends voltage through the enable/clip circuit. The circuit acts as both an output (to enable the audio DSP (Digital Signal Processing) module) and an input (to detect an overload condition). The voltage sent by the ACM (Audio Control Module) passes through a variable resistor in the audio DSP (Digital Signal Processing) module, then to ground. As the audio DSP (Digital Signal Processing) module reaches maximum output, the resistance in the variable resistor decreases. This decreases the voltage drop, resulting in the ACM (Audio Control Module) detecting a higher voltage on the enable/clip circuit. When the voltage reaches the clip threshold, the ACM (Audio Control Module) clips the audio output signal to the audio DSP (Digital Signal Processing) module (heard as distortion), in order to prevent damage to the audio DSP (Digital Signal Processing) module and the speakers.
The enable/clip status is based on the following voltages, as detected by the ACM (Audio Control Module) :
- Less then 0.4 volt: amplifier disabled
- Between 3.8 and 6.7 volts: amplifier enabled
- Greater than 8.5 volts: amplifier clipped
For vehicles with Intelligent Access (IA), the Remote Function Actuator (RFA) module sends a voltage signal to the ACM (Audio Control Module) when the ignition is in a START sequence. This prevents voltage spikes from creating a popping sound during engine cranking. However, if this circuit has a short to voltage or the RFA (Remote Function Actuator) module sends the signal incorrectly, it results in the speaker output being muted.
- DTC B125C:11 (Radio Mute Circuit: Short To Ground)- sets when the RFA (Remote Function Actuator) module detects a short to ground on the mute circuit. This should not cause any observable audio system symptoms.
- DTC B125C:15 (Radio Mute Circuit Short To Battery or Open)- sets when the RFA (Remote Function Actuator) module detects an open or short to voltage on the mute circuit. If a short to voltage exists, the ACM (Audio Control Module) does not enable the audio DSP (Digital Signal Processing) module.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Audio DSP (Digital Signal Processing) module
- ACM (Audio Control Module)
PINPOINT TEST E : POOR QUALITY/DISTORTED/NO SOUND FROM ALL SPEAKERS
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings.
E1 CHECK THE START SIGNAL TO THE ACM (Audio Control Module)
- Ignition OFF.
- Disconnect: ACM (Audio Control Module) C240A.
- Ignition ON.
- Measure the voltage between the ACM (Audio Control Module) C240A-15, circuit CBP28 (GY/VT), harness side and ground.
Is any voltage present?
Yes
If the vehicle is equipped with IA (Intelligent Access), GO to E2.
Otherwise, REPAIR the circuit. TEST the system for normal operation.
No
If the vehicle is equipped with IA (Intelligent Access), GO to E3.
Otherwise, GO to E4.
E2 CHECK THE START SIGNAL FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: RFA (Remote Function Actuator) Module C2153D.
- Ignition ON.
- Measure the voltage between the ACM (Audio Control Module) C240A-15, circuit CBP28 (GY/VT), harness side and ground.
Is any voltage present?
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the RFA (Remote Function Actuator) module self-test. TEST the system for normal operation.
No
INSTALL a new RFA (Remote Function Actuator) module. TEST the system for normal operation.
E3 CHECK THE START SIGNAL FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: RFA (Remote Function Actuator) Module C2153D.
- Measure the resistance between the ACM (Audio Control Module) C240A-15, circuit CBP28 (GY/VT), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to E4.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the RFA (Remote Function Actuator) module self-test. TEST the system for normal operation.
E4 CHECK THE AUDIO DSP (Digital Signal Processing) MODULE VOLTAGE SUPPLY
- Ignition OFF.
- Disconnect: Audio DSP (Digital Signal Processing) Module C4326C.
- Measure the voltage between the audio DSP (Digital Signal Processing) module, harness side and ground as follows:
Positive Meter Lead Negative Meter Lead C4326C-9 SBP40 (VT/RD) Ground C4326C-10 SBP40 (VT/RD) Ground C4326C-11 SBP38 (BN/RD) Ground C4326C-12 SBP38 (BN/RD) Ground
Are the voltages greater than 10 volts?
Yes
GO to E5.
No
VERIFY the Smart Junction Box (SJB) fuse 38 (20A) or fuse 40 (20A) is OK. If OK, REPAIR the circuit in question. CLEAR any DTCs present. TEST the system for normal operation. If not OK, Refer to the Wiring Diagrams to identify the possible causes of the circuit short. Electrical Diagrams
E5 CHECK THE AUDIO DSP (Digital Signal Processing) MODULE GROUND FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the audio DSP (Digital Signal Processing) module, harness side and ground as follows:
Positive Meter Lead Negative Meter Lead C4326C-21 GD149 (BK/GY) Ground C4326C-22 GD149 (BK/GY) Ground C4326C-23 GD149 (BK/GY) Ground C4326C-24 GD149 (BK/GY) Ground
Are the resistances less than 5 ohms?
Yes
GO to E6.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
E6 CHECK THE AUDIO DSP (Digital Signal Processing) MODULE ENABLE CIRCUIT FOR CORRECT VOLTAGE
- Connect: Negative Battery Cable.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the audio DSP (Digital Signal Processing) module C4326A-3, circuit CME31 (BU/GN), harness side and ground.
Is the voltage between 3.8 and 6.7 volts?
Yes
GO to E10.
No
GO to E7.
E7 CHECK THE AUDIO DSP (Digital Signal Processing) MODULE ENABLE CIRCUIT FOR A SHORT TO VOLTAGE
- Disconnect: ACM (Audio Control Module) C240A.
- Ignition ON.
- Measure the voltage between the audio DSP (Digital Signal Processing) module C4326A-3, circuit CME21 (BU/GN), harness side and ground.
Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to E8.
E8 CHECK THE AUDIO DSP (Digital Signal Processing) MODULE ENABLE CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the audio DSP (Digital Signal Processing) module C4326A-3, circuit CME31 (BU/GN), harness side and the ACM (Audio Control Module) C240A-7, circuit CME31 (BU/GN), harness side; and between the audio DSP (Digital Signal Processing) module C4326A-3, circuit CME31 (BU/GN), harness side and ground.
Is the resistance less than 5 ohms between the audio DSP (Digital Signal Processing) module and the ACM (Audio Control Module), and greater than 10,000 ohms between the audio DSP (Digital Signal Processing) module and ground?
Yes
GO to E9.
No
REPAIR the circuit. TEST the system for normal operation.
E9 CHECK FOR CORRECT ACM (Audio Control Module) OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the ACM (Audio Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM (Audio Control Module) connectors and make sure they seat correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes
INSTALL a new ACM (Audio Control Module). REFER to Audio Control Module (ACM) . CLEAR any DTCs present. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR any DTCs present. TEST the system for normal operation.
E10 CHECK FOR CORRECT AUDIO DSP (Digital Signal Processing) MODULE OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the audio DSP (Digital Signal Processing) module connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the audio DSP (Digital Signal Processing) module connectors and make sure they seat correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes
INSTALL a new audio DSP (Digital Signal Processing) module. REFER to Audio Digital Signal Processing (DSP) Module . CLEAR any DTCs present. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR any DTCs present. TEST the system for normal operation.