Can a bm54 radio module be repaired - Car Audio & Video

Remove the radio and have it repaired by one of the many online repair businesses, average cost about $250.

I am not an expert but I think there can be little or no modulation of the carrier wave unless there is an audio input to the modulator. Like any audio amplifier a transmitter modulator (amplitude modulation) is quiescent without an input.

If the modulation amplifier and audio pre-amp are working and modulating the carrier wave and the antenna is ok then audio modulated radio frequency must be being transmitted.

It would be an extremely good quality CB that had a modulation meter. Mostly all they have is a meter giving an indication of the rf power being sent to the antenna and that rf (radio frequency) power would be the same whether modulated or unmodulated.
The modulation envelope, incidentally, is traditionally viewed or measured with an oscilloscope.

The indicated rf power could be verified using a field strength meter but the only practical way to discover if a standard CB is transmitting modulated rf is to listen to the transmission on a suitable receiver. If the squelch is turned down it will be obvious if the rf carrier wave is being received as the hiss would be silenced. If no audio is received it can be assumed none is being transmitted.

I suggest you try another microphone and lead and if that doesn't work it is clearly a job for a repair shop.

Your radio display is backlit with a standard T5 or T10 incandescent bulb, which is replaceable.

Check tr 14 15 AND 16 AND DIODES D14 D13

Do you know what U code's are for ? How did you pull this code ? There is no U0155 , U code's start at
Diagnostic Trouble Code (DTC) List
DTC
Diagnostic Procedure
Modules
U1000
DTC U1000 and U1255
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC, IPM, LMDM, LRDM, MSM, PCM, Radio, Remote Playback Device CD Changer, RCDLR, RIM, RMDM, RRDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car
U1016
DTC U1001-U1254
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC , IPM, LMDM, LRDM, MSM, Radio, RCDLR, RIM, RRDM, RMDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car
U1040
DTC U1001-U1254
IPC, PCM, SDM
U1056
DTC U1001-U1254
EBCM, PCM
U1064
DTC U1001-U1254
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC, IPM, LMDM, LRDM, MSM, PCM, Radio, RCDLR, Remote Playback Device CD Changer, RIM, RMDM, RRDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car
U1065
DTC U1001-U1254
DDM, DIM, ESC, FPDM, IPC, LMDM, LRDM, VCIM, HVAC Control Module - Auxiliary, PCM, Radio, RIM, RMDM, RRDM, VCIM
U1066
DTC U1001-U1254
DDM, FPDM, IPC, IPM, PCM
U1088
DTC U1001-U1254
IPC
U1096
DTC U1001-U1254
PCM, SDM
U1128
DTC U1001-U1254
Audio Amplifier, Cellular Telephone Module, Digital Radio Receiver, Remote Playback Device CD Changer, VCIM
U1129
DTC U1001-U1254
Radio
U1130
DTC U1001-U1254
Radio
U1137
DTC U1001-U1254
Radio
U1144
DTC U1001-U1254
IPC, Radio
U1151
DTC U1001-U1254
Radio
U1160
DTC U1001-U1254
IPC, RIM
U1161
DTC U1001-U1254
IPC, RIM
U1162
DTC U1001-U1254
IPC, RIM
U1163
DTC U1001-U1254
IPC, RIM
U1164
DTC U1001-U1254
DDM, Digital Radio Receiver, DIM, FPDM, IPC, LRDM, MSM, VCIM, Radio, RIM, RRDM, Steering Column Module
U1165
DTC U1001-U1254
DDM, FPDM, LRDM, RRDM
U1176
DTC U1001-U1254
IPC
U1192
DTC U1001-U1254
IPC, PCM
U1255
DTC U1000 and U1255
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC, IPM, LMDM, LRDM, MSM, PCM, Radio, Remote Playback Device CD Changer, RCDLR, RIM, RMDM, RRDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car
U1300
DTC U1300, U1301, or U1305
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC, IPM, LMDM, LRDM, MSM, PCM, Radio, Remote Playback Device CD Changer, RCDLR, RIM, RMDM, RRDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car
U1301
DTC U1300, U1301, or U1305
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC, IPM, LMDM, LRDM, MSM, PCM, Radio, Remote Playback Device CD Changer, RCDLR, RIM, RMDM, RRDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car
U1305
DTC U1300, U1301, or U1305
Audio Amplifier, Cellular Telephone Module, DDM, DDSA, Digital Radio Receiver, DIM, EBCM, ESC, FPDM, HVAC Control Module - Auxiliary, IPC, IPM, LMDM, LRDM, MSM, PCM, Radio, Remote Playback Device CD Changer, RCDLR, RIM, RMDM, RRDM, SDM, Steering Column Module, Theft Deterrent Control Module, VCIM, Window Switch - Front Passenger w/armored car

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serial data line is the means by which the microprocessor-controlled modules in the vehicle communicate with each other. Once the scan tool is connected to the class 2 serial data line through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. This value is an average; class 2 uses a variable pulse width modulation to carry data and depending on the message it may operate faster or slower. The bus will float at a nominal 7 volts during normal operation. Each module can pull this lower during the transmission. The bus is not at battery positive voltage or ground potential during normal operation. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example, if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating; for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

Your best bet ,take it to a qualified repair shop.

Hello Richard, when the ulf module was installed, was the jumper plug installed in the blue 26 pin connector in the left rear corner near the GPS unit. I think that if this plug is missing, you will not get any sound for the interface. This plug is required for vehicles with nav. I think it is called the Voice Input jumper plug.

In the back is where power mods have been added...It sounds like a swing kit 1/2 watt deadkey to 25 watts which is a powerful modulation exceeding 100%. Its a 220uf capacitor in place of a jumper J1 or J(x) J something in some radios. if you replace the jumper and remove the capacitor 220uf or 470uf one.(near finals it will return to around 4 watt dead key) The result of 4 watts is modulation is flat;where if you adjust it to 2 1/4 watt to say 20 watts it will be very loud and modulation is at 100%.

This is generally caused by nothing more than dry solder joints. Adding more solder to the pcb 'attachments' usually works. Certainly a first step!

Assuming that you've tried another mike, the problem may lie in the speech amplifier circuit within the radio, something that will require someone with technical knowledge to repair.