What does it mean?
B1906 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Immobilizer-Keyless Control Unit Lost Communication with Gauge Control Module (A/T Message) .
Symptoms
- Gear position display on the instrument cluster is blank, frozen or wrong
- Key removal or shift interlock warnings appear at the wrong time, or the key cannot be removed
- Keyless entry and start functions become restricted or unreliable
- Warning chimes for door open or key in ignition stop working
- Other communication codes are usually stored in several modules at once
Likely causes
- Open or shorted communication wire between the cluster and the keyless control unit
- Blown fuse or interrupted power supply to the instrument cluster
- Poor cluster ground behind the dash, often loosened during dash or radio work
- Corroded, loose or partly unlatched cluster connector
- Transmission range information not being transmitted upstream, so the cluster has nothing to relay
- Faulty instrument cluster or faulty keyless control unit
- General bus disturbance caused by another failing module on the same network
How to fix it
- Scan every module and record which ones respond, because a shared communication fault rarely affects only one unit
- Check the instrument cluster fuse, its supply voltage and its ground with a voltage drop test
- Compare the gear position shown on the cluster with the range value read by the scan tool to see where the information stops
- Measure the communication line between the cluster and the keyless control unit for continuity and for shorts to ground or power
- Inspect and reseat both module connectors, looking for corrosion, pushed back terminals and moisture
- Disconnect any aftermarket device wired into the network and retest
- Replace the keyless control unit only when the cluster, wiring and network have all tested good