Pinpoint Test K: Poor Quality/Distorted/No Sound From One Or More Speakers (Not All Speakers) - Navigation Without THX(R) Sound
Information and Entertainment System
Pinpoint Tests
Pinpoint Test K: Poor Quality/Distorted/No Sound From One Or More Speakers (Not All Speakers) - Navigation Without THX(R) Sound
Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information. Diagrams By Number
Normal Operation
The Audio Control Module (ACM) directs audio signals to the audio amplifier in the form of an AC voltage. The amplifier boosts the audio signals and sends them to the speakers. The ACM provides internal circuit protection for shorts to ground or shorts to voltage.
A short to ground or short to voltage in the circuitry to one of the speakers may cause multiple speakers to lose sound due to the built-in overload protection feature of the ACM. In this case, a speaker fault DTC sets, and this pinpoint test should be followed to isolate the damaged circuit.
It should also be noted that when the ACM activates the built-in overload protection, DTC B1342 may also be set. The circuit failure must be repaired before DTC B1342 can be cleared.
To enable the audio amplifier, the ACM sends voltage through the enable/clip circuit. The circuit acts as both an output (to enable the amplifier) and an input (to detect an amplifier overload condition). The voltage sent by the ACM passes through a variable resistor in the audio amplifier, then to ground. As the amplifier reaches maximum output, the resistance in the variable resistor decreases. This decreases the voltage drop, resulting in the ACM detecting a higher voltage on the enable/clip circuit. When the voltage reaches the clip threshold, the ACM clips the audio output signal to the amplifier (heard as distortion), in order to prevent damage to the amplifier and speakers.
The enable/clip status is based on the following voltages, as detected by the ACM:
- Less then 0.4 volt: amplifier disabled
- Between 3.8 and 6.7 volts: amplifier enabled
- Greater than 8.5 volts: amplifier clipped
An open in the enable/clip circuit causes the speakers to produce no sound because the enable signal does not reach the audio amplifier. A short to ground or short to voltage can cause severe distortion to be heard in the speakers. In either of these scenarios, the subwoofer should continue to operate correctly, as it utilizes a separate amplifier and enable/clip circuit.
It is also important to note that if the navigation voice guidance setting is set too low, it may appear that the front speakers intermittently produce no sound. Make sure the voice guidance setting is set high enough to hear the voice guidance commands before addressing a concern with the front speakers.
The speaker walk test can be used to isolate a concern with a particular speaker. This can reduce the diagnostic steps necessary to isolate the concern. To carry out the speaker walk test, refer to Audio Control Module (ACM) Self-Diagnostic Mode Audio Control Module (ACM) Self-Diagnostic Mode.
B1A01:01-B1A04:01:
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Speaker
- Audio amplifier
- ACM
PINPOINT TEST K: POOR QUALITY/DISTORTED/NO SOUND FROM ONE OR MORE SPEAKERS (NOT ALL SPEAKERS) - NAVIGATION WITHOUT THX(R) SOUND
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. Refer to Battery.
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K1 DETERMINE THE INOPERATIVE SPEAKER(S)
NOTE: For MKX, if the concern is with a tweeter speaker, GO to step K2. For all other MKX concern, GO to step K5.
- Carry out the speaker walk test. Refer to Audio Control Module (ACM) Self-Diagnostic Mode Audio Control Module (ACM) Self-Diagnostic Mode.
- Is the concern with the subwoofer speaker?
Yes
Go To Pinpoint Test E. Pinpoint Test E: The Subwoofer Is Inoperative/Does Not Operate Correctly - Audiophile
No
If the concern is with a tweeter speaker only, GO to K2.
For all other concerns, GO to K5.
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K2 CHECK THE AUDIO SIGNALS TO THE SUSPECT TWEETER SPEAKER
- Ignition OFF.
- Disconnect: Suspect Tweeter Speaker.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the AC voltage between the suspect tweeter speaker pin 1 and pin 2, harness side as follows:
- Is a fluctuating AC voltage present?
Yes
INSTALL a new speaker for the suspect tweeter speaker. REFER to Speaker - A-Pillar Speaker - A-Pillar. TEST the system for normal operation.
No
GO to K3.
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K3 CHECK THE CIRCUITS TO THE SUSPECT TWEETER SPEAKER FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: LF Door Speaker C570b (LH Speaker Concern) or RF Door Speaker C612b (RH Speaker Concern).
- Ignition ON.
- Measure the voltage between the suspect tweeter speaker, harness side and ground as follows:
- Is any voltage present?
Yes
REPAIR the circuit in question. TEST the system for normal operation.
No
GO to K4.
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K4 CHECK THE CIRCUITS TO THE SUSPECT TWEETER SPEAKER FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the suspect tweeter speaker, harness side and the respective door speaker, harness side; and between the suspect tweeter speaker, harness side and ground as follows:
- Is the resistance less than 5 ohms between the suspect tweeter speaker and the door speaker, and greater than 10,000 ohms between the suspect tweeter speaker and ground?
Yes
INSTALL a new door speaker. REFER to Speaker - Door Speaker - Door. TEST the system for normal operation.
No
REPAIR the circuit in question. TEST the system for normal operation.
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K5 CHECK THE AUDIO SIGNALS TO THE SUSPECT SPEAKER
- Ignition OFF.
- Disconnect: Suspect Speaker.
- Operate the audio system in radio tuner (AM/FM), single-play mode.
- Measure the AC voltage between the suspect speaker pins, harness side as follows:
- Is a fluctuating AC voltage present?
Yes
INSTALL a new speaker for the suspect speaker. REFER to Speaker - Door Speaker - Door. TEST the system for normal operation.
No
GO to K6.
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K6 CHECK THE AUDIO AMPLIFIER VOLTAGE SUPPLY
- Ignition OFF.
- Disconnect: Audio Amplifier C4364b.
- Measure the voltage between the audio amplifier C4364b-1, circuit SBP18 (YE/RD), harness side and ground; and between the audio amplifier C4364b-8, circuit SBP18 (YE/RD), harness side and ground.
- Are the voltages greater than 10 volts?
Yes
GO to K7.
No
VERIFY the Smart Junction Box (SJB) fuse 18 (20A) is OK. If OK, REPAIR the circuit in question. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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K7 CHECK THE AUDIO AMPLIFIER GROUND CIRCUITS FOR CONTINUITY
- Disconnect: Negative Battery Cable.
- Measure the resistance between the audio amplifier C4364b-7, circuit GD148 (BK/YE), harness side and ground; and between the audio amplifier C4364b-14, circuit GD148 (BK/YE), harness side and ground.
- Are the resistances less than 5 ohms?
Yes
GO to K8.
No
REPAIR the circuit in question. TEST the system for normal operation.
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K8 CHECK THE AUDIO SIGNALS TO THE AUDIO AMPLIFIER
- Ignition OFF.
- Connect: Negative Battery Cable.
- Connect: Audio Amplifier C4364b.
- Disconnect: Audio Amplifier C4364a.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the AC voltage between the audio amplifier pins, harness side as follows:
- Is a fluctuating AC voltage present?
Yes
GO to K9.
No
GO to K14.
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K9 CHECK THE AUDIO AMPLIFIER ENABLE CIRCUIT VOLTAGE
- Ignition OFF.
- Disconnect: Audio Amplifier C4364b.
- Operate the audio system in radio tuner (AM/FM).
- Measure the voltage between the audio amplifier C4364b-9, circuit CME31 (BU/GN), harness side and ground.
- Is the voltage between 3.8 and 6.7 volts?
Yes
GO to K12.
No
GO to K10.
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K10 CHECK THE AUDIO AMPLIFIER ENABLE CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: ACM C240a.
- Ignition ON.
- Measure the voltage between the audio amplifier C4364b-9, circuit CME31 (BU/GN), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to K11.
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K11 CHECK THE AUDIO AMPLIFIER ENABLE CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the audio amplifier C4364b-9, circuit CME31 (BU/GN), harness side and the ACM C240a-7, circuit CME31 (BU/GN); and between the audio amplifier C4365b-9, circuit CME31 (BU/GN), harness side and ground.
- Is the resistance less than 5 ohms between the audio amplifier and the ACM, and greater than 10,000 ohms between the audio amplifier and ground?
Yes
GO to K16.
No
REPAIR the circuit. TEST the system for normal operation.
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K12 CHECK THE SPEAKER CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Suspect Speaker.
- Measure the voltage between the suspect speaker, harness side and ground as follows:
- Is any voltage present?
Yes
REPAIR the circuit in question. TEST the system for normal operation.
No
GO to K13.
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K13 CHECK THE SPEAKER CIRCUITS FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the audio amplifier, harness side and the suspect speaker, harness side; and between the audio amplifier, harness side and ground as follows:
- Are the resistances less than 5 ohms between the audio amplifier and the suspect speaker, and greater than 10,000 ohms between the audio amplifier and ground?
Yes
INSTALL a new audio amplifier. REFER to Audio Amplifier Service and Repair. TEST the system for normal operation.
No
REPAIR the circuit in question. TEST the system for normal operation.
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K14 CHECK THE AUDIO CIRCUITS TO THE AUDIO AMPLIFIER FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: ACM C240a.
- Ignition ON.
- Measure the voltage between the audio amplifier, harness side and ground as follows:
- Is any voltage present?
Yes
REPAIR the circuit in question. CLEAR any DTCs present. TEST the system for normal operation.
No
GO to K15.
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K15 CHECK THE AUDIO CIRCUITS TO THE AUDIO AMPLIFIER FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the audio amplifier, harness side and the ACM, harness side; and between the audio amplifier, harness side and ground as follows:
- Are the resistances less than 5 ohms between the audio amplifier and the suspect module, and greater than 10,000 ohms between the audio amplifier and ground?
Yes
GO to K16.
No
REPAIR the circuit in question. CLEAR any DTCs present. TEST the system for normal operation.
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K16 CHECK FOR CORRECT ACM OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the ACM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM 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. REFER to Audio Control Module (ACM) Audio Control Module (ACM). 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.
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