What does it mean?
U1950 is a Network (CAN bus, module communications) fault code. It indicates: BCM Command (From Body Control Module) Message CRC Or Message Counter Fault .
Symptoms
- Several body functions misbehave — lighting, central locking, wipers, alarm
- Warning lamps on the cluster with no mechanical fault behind them
- Functions work sometimes and fail at other times with no pattern
- Modules drop off and reappear on the scan tool
- Battery drain because a module never goes to sleep
- Codes return quickly after being cleared
Likely causes
- Corrupted messages caused by a poor connection or electrical interference on the bus
- High resistance in the bus wiring from corroded terminals or a failing splice
- Chafed bus wire shorting intermittently to ground or to an adjacent circuit
- BCM with a poor power supply or ground, resetting in the middle of a transmission
- Software mismatch between the BCM and the receiving module after a partial update
- Internal BCM fault producing wrong checksums
- Aftermarket electronics injecting noise onto the bus
How to fix it
- Record all stored codes in every module before clearing anything
- Check the BCM power supplies, its fuses and its grounds with a voltage drop test
- Inspect the BCM connectors for pushed-back terminals, corrosion and moisture
- Wiggle-test the harness while watching live data for message dropouts
- Disconnect aftermarket electrical accessories and see whether the fault clears
- Verify that all modules that must work together carry compatible software levels, and update if not
- Replace the BCM only after wiring, supply and software have been ruled out