ABS and PSM Warning Lights ON on my 2019 718 Cayman S

ClearTheCode admin answer:

When both the ABS (Anti-lock Braking System) and PSM (Porsche Stability Management) warning lights illuminate simultaneously on your 2019 Porsche 718 Cayman S, it typically indicates a shared fault within the vehicle's dynamic driving systems. These systems are highly integrated, and a problem affecting one often impacts the other.

Here are the most common causes:

1. Wheel Speed Sensors (Most Common):

   • Each wheel has a speed sensor that provides crucial data to the ABS and PSM control units. If one of these sensors fails, becomes dirty, gets damaged, or its wiring is compromised, both systems will lose vital information and trigger a fault.
   • Common OBD Codes: These would typically be C-codes (Chassis codes), such as C0031 (Left Front Wheel Speed Sensor Circuit Malfunction) or similar codes for other wheels.

2. Wiring Harness Issues:

   • Damage or corrosion in the wiring leading to any of the wheel speed sensors or the ABS/PSM control module can interrupt communication and cause these lights to come on.

3. ABS/PSM Control Module Failure:

   • While less common, the ABS/PSM control module itself can fail. This module processes all the sensor data and controls the braking and stability functions. A fault here would naturally affect both systems.

4. Brake Fluid Level:

   • A very low brake fluid level can sometimes trigger these warnings, as it impacts braking system performance. Check your brake fluid reservoir level.

5. Steering Angle Sensor:

   • The steering angle sensor provides input to the PSM system about the driver's steering input. A fault here can confuse the PSM, leading to warnings.

6. Tire Pressure/Size Mismatch:

   • While usually triggering a separate TPMS light, significant differences in tire pressure or incorrect tire sizes (especially if different from OEM specifications) can sometimes confuse the PSM system.

What to Do:

• Professional Diagnosis is Key: The most effective way to diagnose this issue is to take your 718 Cayman S to a Porsche dealership or a reputable independent shop with a specialized diagnostic scanner (like Porsche PIWIS). A standard OBD-II scanner might only show generic codes, but a Porsche-specific tool can read the detailed C-codes from the ABS/PSM module, pinpointing the exact sensor or component causing the fault.
• Do not ignore: While the car may seem to drive normally, your ABS and PSM systems are likely deactivated or operating in a reduced capacity, which can compromise safety, especially in emergency braking or slippery conditions. Get it checked out promptly.