What does it mean?
C1126 is a Chassis (ABS, traction control, steering) fault code. It indicates: TPMS ECU Battery Voltage Low .
Symptoms
- Tyre pressure warning lamp on or flashing at start up
- Pressure values missing or shown as dashes on the display
- Sensors intermittently reported as not received
- Fault appears on cold starts and disappears after driving
- Other modules also log low voltage codes
- Warning returns after the vehicle has been parked for several days
Likely causes
- Battery low on charge or nearing the end of its service life
- Corroded or loose terminals at the module connector or its fuse
- Poor module ground, frequently a rusted body stud behind interior trim
- Voltage drop in a long supply wire with an oxidised splice
- Charging system underperforming, for example a worn alternator or a slipping belt
- Parasitic drain that leaves the battery low every morning
- Water reaching the module location after a leak from a seal or drain
How to fix it
- Test the battery and measure charging voltage at idle and under electrical load
- Check the module fuse and inspect the holder for corrosion and heat damage
- Back probe the module connector and record the supply voltage with the key on
- Perform voltage drop tests on the supply and ground of the module
- Clean and tighten the module ground point and inspect for water damage nearby
- Repair the corroded terminal or damaged supply wire
- Clear the code, relearn the sensors if required, and confirm all pressures are displayed