Three of the most common causes for traction control problems include faulty signalling from one of the car's wheel speed sensors, a pump failing to run or a leak in the TCS/ABS system's high pressure accumulator. Pump problems may be mechanical or electrical in nature.
Many new cars that have TCS/ABS systems installed also carry diagnostic software that produces codes indicating what types of mechanical or electrical problems the car may have. These diagnostics systems include tests that operate the wheel sensors, traction pump, modulator assembly and the TCS/ABS solenoids individually to determine the specific cause of various traction problems.
If the test code indicates that the wheel speed sensors fail to transmit signals properly, the faulty sensor may require replacement. In some cases, simply cleaning the sensor can improve the signal. A mechanic can test a failed pump by bypassing its relay with a fused jumper wire. If the pump still fails to run after that, it must be replaced.
High-pressure accumulators need to be sealed tightly against the adjacent modulator or pump assembly. If the rubber diaphragm inside the accumulator has ruptured over time, causing failure due to depressurization, a mechanic must fully depressurize the device and then replace the entire accumulator.