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Low voltage codes

Stan S

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Yesterday I got a service soon light. Checked the codes and had U1255 (serial data malfunction) current. Also history B1327 (device power low), B0856 (device power low), B0856 (+5 volt out of range), U1300 (short to ground). I cleared the codes and the service soon light is off and no codes. It appears to be a low voltage problem. The volt meter varys between 13.2 and 13.6 volts. Is this normal? I was thinking 13.6 volts and up. It appears I might have a battery going bad or maybe the alternator. I don't understand the U1300 code, any ideas? Thanks, Stan

99 Concours, 90k mi.

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The voltage you read on the DIC with engine running and normal electrical load depends on many variables including battery condition, amount of demand from various loads, alternator condition and many others. The easiest one to forget is battery temperature.

Generally speaking, if your battery will crank and start a heat-soaked engine, both your battery and alternator can be considered to be working fine.

Has your battery been completely discharged?


Drive your car.

Use your cell phone.


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