What does it mean?
C1508 is a Chassis (ABS, traction control, steering) fault code. It indicates: Left Rear Tire Pressure Trigger Module Performance .
Symptoms
- Tyre pressure warning lamp with a system fault message that returns after each relearn
- Left rear pressure value appears late, drops out or swaps with another position
- Relearn works occasionally and fails at other times
- Warning lamp behaviour changes with weather, being worse in wet conditions
- Tyres hold pressure normally
Likely causes
- Trigger module electrically weak: it powers up but produces a low strength trigger field
- High resistance in the supply or ground circuit from corroded terminals
- Partly chafed harness causing an intermittent fault that comes and goes with suspension movement
- Trigger module mounted too far from the wheel or behind an added liner or underseal
- Wheel sensor with a dying battery that only answers sometimes
- Water damage inside the module housing after long term exposure
- Receiver module unable to interpret the response because of a software or configuration mismatch
How to fix it
- Run a relearn twice and record whether the failure point is consistent
- Trigger the left rear sensor directly and check its battery status and signal strength
- Measure voltage and ground quality at the trigger module while the system is active
- Perform a wiggle test on the rear harness with the module powered to catch an intermittent break
- Inspect the module mounting position and clearance to the wheel
- Check the receiver configuration and software level if components were replaced
- Replace the trigger module, complete the relearn and verify the position holds after a road test