In this guide, we will go over problems that trigger Porsche Anti-lock Brake System (ABS) and Porsche Stability Management (PSM) to malfunction and how to diagnose it yourself using an OBD-II scanner.
What does Porsche ABS/PSM light mean?
Porsche ABS light may stay on when the Anti-lock Brake System detects a problem with one of the wheel speed sensors or the ABS module malfunctions.
Once your Porsche ABS fails, other systems such as the traction control system will get disabled as well because those systems depend on a working ABS to function correctly.
If you Porsche ABS or PSM warning lights stay on all the time drive carefully. Keep in mind the vehicle can take longer to bring to a stop and is more likely to skid when braking.
If the ABS and the red BRAKE light stay on with exclamation mark, stop immediately. Check the brake fluid level and correct it if necessary. Do not continue driving with the BRAKE light on.
When your Porsche ABS or PSM system malfunctions you may notice:
- ABS light stays on
- PSM warning light or message
- ABS failure message shows on the dashboard
- Brake light stays on
- The vehicle goes in limp mode
Common problems that trigger Porsche ABS and PSM lights to stay on:
- ABS wheel speed sensor defective
- PSM module faulty
- Steering angle sensor
- MAF Sensor
- Brake light switch
- Low brake fluid level
- Damaged wire harness
- Low battery voltage
- Corroded battery posts
To find out why your Porsche ABS/PSM lights are on, you should read the fault codes from the ABS menu. You can read the codes yourself or have a Porsche mechanic do it for you.
How to diagnose Porsche ABS / PSM
To diagnose the ABS and PSM systems, you will need an OBD-II scanner that can read and clear Porsche specific fault codes. Generic OBD-II scanners are not able to access those systems and will not show a fault code.
What you will need
- Park your Porsche on a level surface and set the parking brakes.
- Locate the diagnostic port under the dashboard and plugin your OBD-II scanner.
- Turn on the ignition but do not start the engine.
- Depending on the scanner, it should turn on automatically. If not press the power button. From the main menu, select Porsche and then the model. Next, you should see all the modules listed. Select either ABS or PSM. Scroll down to Read Faults.
- Write down all the fault codes. If the codes are STORED status, go back to the main menu and this time select Clear fault codes. If you can't clear the codes, the chances are that the problem that triggered the warning light is not fixed yet.
Common problems that trigger Porsche ABS and PSM lights to stay on include:
ABS Wheel Speed Sensor
One of the most common issues that trigger Porsche ABS or PSM light to come on is a faulty ABS wheel speed sensor. The sensors can fail and stop sending wheel speed readings to the ABS module. They can also get damaged by rocks as well.
If you have an OBD-II scanner that can read faults from the ABS module, you can go to ABS or PSM control unit then under that select Live Data. Here you can see speed values from all the wheels as you carefully drive the vehicle.
Replacing the Porsche ABS wheel speed sensor is a straightforward procedure that you can perform yourself.
If the ABS/PSM light stays on and the fault code still points to a faulty ABS sensor check the wire harness. If wire harness from the sensor to the ABS module is ok, the problem could be the ABS module.
Mass Air Flow (MAF) Sensor
It may sound unrelated, but a faulty MAF sensor or vacuum leak can trigger ABS and PSM fault lights to come on, especially if those warning lights come on during hard acceleration.
When you read the codes you may get DME fault codes such as 5525 - Torque transmission disturbed at times or P0102 - Mass or Circuit Airflow (MAF) Circuit Low Voltage Input.
It is strongly recommended that you install a genuine Porsche MAF sensor made by Bosch, which is the OEM supplier. Also, avoid using air filters that need frequent oiling.
ABS Module / Pump
The ABS module is the "brains" of ABS and PSM systems. It controls the brake pressure sent to each wheel. It also adjusts the braking force to those wheels when the PSM system detects that the vehicle has lost traction.
Porsche ABS module can fail for several reasons:
- loose terminals
- Weak joints inside the module, causing intermittent ABS/PSM light.
- worn brushes for the ABS motor typical on high mileage Porsche
- corrosion at the ABS terminals
- Brake fluid leaking on the ABS pump causing loss of communication with multiple wheel speed sensors.
Bosch makes ABS modules installed on many Porsche vehicles as Porsche doesn't make their own ABS module.
If your mechanic determines that the ABS module is faulty, it can be replaced with a used unit, but it may require coding. A cheaper alternative is to have your existing Porsche ABS Module Repaired.
Steering Angle Sensor
The steering angle sensor (SAS) sends data to the PSM module to let it know which way the steering wheel is turned. The steering angle sensor may be out of calibration and send the wrong information to the PSM module.
On some models, the steering angle sensor and clock spring are integrated into one piece and need to be replaced as one unit. Before you replace this expensive part, carry out steering angle calibration as that will often fix the ABS and PSM problems.
The steering angle sensor is located on the steering column. To replace it you will need to remove the steering wheel. You need to have the battery disconnected, or you will trigger the airbag light. Once you return the SAS, you need to carry out steering angle sensor calibration.
Brake Light Switch
If you are getting ABS failure and PSM failure drive to workshop message on the dashboard when you press the brake pedal or start to drive the problem may be the brake light switch.
This problem can affect any Porsche, including 911, Cayman, The brake light switch is very inexpensive and takes only a few minutes to replace. Porsche brake light switch is mounted above the brake pedal.
You can't determine if the brake light switch is defective or not by looking at the brake lights.
To determine why your Porsche ABS and PSM lights come on, you need to diagnose the problem. Start by reading the fault codes from the ABS module. Do not replace parts based on what you read online.
Pay attention when installing anew brake light switch. The switch has a self-adjusting mechanism. Check the operation of the plunger after you replace the brake light switch.
Related fault codes: P0571, P1574 - Brake switch signal implausible. 4340 stop light switch defective, Porsche DME fault code 364.
If your Porsche ABS light is caused by no signal coming from the wheel speed sensor, inspect, clean and if needed, replace the faulty wheel speed sensor.
In some cases, the wheel speed sensor may appear faulty because the wire that goes from the ABS module to the wheel speed sensor gets damaged. You can use a digital multimeter to test the connections from the ABS pump to the wheel speed sensor connector.