Category: How Things Work

When wheel slip is noted while the brake is not applied, the ABS Computer-(EBCM) will enter traction control mode.

First, the EBCM requests the PCM to reduce the amount of torque to the drive wheels via the requested torque signal circuit. The PCM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The PCM reports the amount torque delivered to the drive wheels via the delivered torque signal circuit.


If the engine torque reduction does not eliminate drive wheel slip, the EBCM will actively apply the drive wheel brakes. During traction control braking, hydraulic pressure in each drive wheel circuit is controlled to prevent the drive wheels from slipping. The master cylinder isolation valve closes in order to isolate the master cylinder from the rest of the hydraulic system. The prime valve then opens in order to allow the pump to accumulate brake fluid in order to build hydraulic pressure for braking. The drive wheel inlet and outlet solenoid valves then open and close in order to perform the following functions:

Pressure Hold

Pressure Increase

Pressure Descrease

More Auto Repair Help

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    Comments (3)
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    • Guest - Kim Benfield

      My question is why the traction light is coming on my 2005 Chevy impala. What can be done to fix the problem. It doesn't do it all the time. It like it is grabbing and not want to move forward when applying the gas pedal.

    • Guest - Tech

      Soak it with WD-40 for awhile. May have to use a chisel and hammer to sort of break it loose. Tap a slot in the plug, then angle the chisel so when you tap on it you are trying to walk it around. It may just pop loose after a few taps. Worst case for this problem, you may have to heat it.

    • Guest - Jim

      I went to a quick change oil shop today to have my rear end grease changed on my 2000 Silverado. They were unable to remove the plug and rounded off the 3/8 plug hole. Any ideas would be be helpful. Thanks, Jim

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    How Things Work

    Vehicle Front Suspension Operation

    The front suspension has 2 primary purposes:

    Isolate the driver from irregularities in the road surface.
    Define the ride and handling characteristics of the vehicle.

    The front suspension absorbs the impact of the tires travelling over irregular road surfaces and dissipates this energy throughout the suspension system. This process isolates the vehicle occupants from the road surface.


    Common Engine Codes

    Oxygen Sensor Code P0036 and P0056

    P0036 - P0056
    Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature.