What does it mean?
C1504 is a Chassis (ABS, traction control, steering) fault code. It indicates: Tire Pressure Sensor 4 Internal .
Symptoms
- Tyre pressure warning lamp on, often with a system fault message rather than a low pressure warning
- The fourth wheel position shows dashes or a frozen value
- Relearn procedures stop or fail at that wheel
- Correct pressure in the tyre despite the warning
- No change in ride or handling
Likely causes
- Sensor internal battery at the end of its life, so the transmission interval fails
- Sensor body or valve stem damaged while mounting or dismounting the tyre
- Corroded aluminium valve stem, a common issue where road salt is used
- Water inside the sensor after seal failure
- Pressure port blocked by tyre sealant or balancing compound
- Sensor loosened on the rim and struck by the tyre bead
- Replacement sensor with a wrong protocol or an unregistered ID
How to fix it
- Read all sensor IDs, pressures and battery status with a TPMS tool
- Activate each sensor individually to find the one that does not answer
- Verify pressure mechanically with a gauge
- Check the ID registered for that position against the sensor fitted
- Inspect the stem, nut and seal for corrosion and cracks once dismounted
- Replace the sensor, program the ID and complete the wheel position relearn
- Verify all sensors report, then clear the code