Tech Tips (by ALLDATA): Porsche anti-lock brake system light on

Mileage: 128,009

Problem: The vehicle was brought to the shop because the anti-lock brake system (ABS) Light was flashing.

Details: The technician retrieved the following diagnostic trouble codes (DTCs):

• P04201 – RF wheel speed sensor
• P04211 – RR wheel speed sensor
• P04212 – LR wheel speed sensor

Upon inspection, the technician found the wheel speed sensor connectors were broken. He replaced both rear ABS sensors and connectors. During the road test, the ABS light came back on and the original DTCs returned. After clearing the DTCs again, he road tested the car with a scan tool connected to check for wheel speed sensor operation while driving. All the sensors read the correct speed values until 35 mph, at which point, the ABS light came back on and the scan tool lost communication with ABS control module. All the previous DTCs returned.

This is when the technician called Tech-Assist for advice. The Tech-Assist consultant recommended removing the ABS module cover for inspection. The technician found that brake fluid from the hydraulic unit had been leaking into the ABS module and damaged it.

Confirmed Repair: He replaced the entire ABS unit and bled the brakes. The DTCs were cleared and the car taken on a long test drive. The DTCs did not return and the problem was fixed.