What does it mean?
B1255 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Combination Switch Control Unit Lost Communication with MICU (MICU Message) .
Symptoms
- Stalk controlled functions such as wipers, turn signals, headlamps, or high beams stop responding
- Automatic light and intermittent wiper features are dead
- Warning lamps illuminate in the instrument cluster
- Functions may return after a key cycle and then fail again
- Other body modules store communication codes at the same time
Likely causes
- Open or shorted communication line between the combination switch control unit and the body control module
- Loose, corroded, or backed-out terminals at either module connector
- Loss of power or ground at the combination switch control unit
- Internal failure of the combination switch control unit
- Failure of the body control module itself or of its supply circuit
- Aftermarket alarm, remote start, or audio wiring spliced into the communication line
- Water intrusion at the steering column or under-dash fuse box
How to fix it
- Record all stored body codes across every module to see whether one node or the whole network is affected
- Check battery voltage first, then the power feed and ground at the combination switch control unit
- Inspect the connectors at the steering column and at the body control module for corrosion, moisture, and loose pins
- Measure the communication line for continuity between the two modules and for shorts to ground or battery
- Disconnect any aftermarket electrical accessories and retest immediately
- Repair the wiring fault; if the line is proven good, replace the failed unit and configure it as required