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

Leave your comments

Post comment as a guest


    Comments (3)
    Subscribe To These Comments-----   

    • 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

    Latest Articles

    Impala Flashing Engine Light

    I have a 2003/2004 impala i was driving it on the high way ...

    Hyundai Tucson 2016 A/C Blows ...

    2016 Hyundai Tucson. A/C worked great, parked the car for a ...

    Chevrolet Blazer Lost Power ...

    2000 blazer 4x4 lost power to drivetrain going down the ...

    Dodge Durango Timing Chain ...

    My 03 Dodge Durango 4.7L engine was blowing white smoke ...

    2002 Chevy Blazer Keeps ...

    My 2002 blazer keeps dying on me when I am driving, and ...

    How Things Work

    Evaporative Emission System Operation and Components

    The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapors from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor. When the engine is able to use the extra fuel vapor,


    Common Engine Codes

    Knock Sensor Codes P0325 and P0327

    The powertrain control module (PCM) contains integrated knock sensor (KS) diagnostic circuitry. The KS produces an AC voltage at all engine speeds and loads. The PCM then adjusts spark timing based on the amplitude and frequency of the KS signal.