B1A04 Code: Meaning, Causes, and Symptoms | OBD2 Codes

B1A04 – Speaker 4 General Electric Failure


B1A04 Possible Symptoms


Engine Light ON (or Service Engine Soon Warning Light)


B1A04 Possible Causes


Blown Audio Fuse,Faulty Speaker,Speaker harness is open or shorted,Speaker circuit poor electrical connection,Faulty Audio amplifier,Faulty Subwoofer amplifier,Faulty Audio Control Module (ACM)


B1A04 Description


The Audio Control Module (ACM) directs audio signals to the audio amplifier and to the subwoofer amplifier in the form of an AC voltage. The amplifiers boost the audio signals and send 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. To enable the amplifiers, the ACM sends voltage through individual enable/clip circuits. The circuits act as both an output (to enable the amplifier) and an input (to detect an overload condition). The voltage sent by the ACM passes through a variable resistor in each 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 than 0.4 volts: amplifier disabled – Between 3.8 and 6.7 volts (nominal): amplifier enabled – Greater than 8.5 volts: amplifier clipped An open in the enable/clip circuit causes the speakers powered by that particular amplifier 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.