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Chevrolet 6L90 Hill Start Assist Inoperable


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A 2016 Chevrolet Silverado 4×4 had a remanufactured transmission installed. The vehicle came back with a complaint of the “Hill Hold Assist” feature was not working since the remanufactured transmission was installed. The only trouble code stored was an ABS system code for a yaw sensor. The yaw sensor issue was resolved but it did not cure the hill hold complaint.


The vehicle was raised into the air for inspection. What was found was the vehicle speed sensor located in the transfer case extension housing, refer to figure 1, was not plugged all the way into the sensor.

Figure 1


After the VSS connector was connected properly, the hill hold assist feature returned to proper working condition.


Hill Hold Assist makes it easier for the driver to pull away from a stopped position on an uphill or downhill slope. This prevents the vehicle from rolling backwards or forward on the slope.


Hill Hold Assist applies the vehicle’s brakes for 1.5 seconds when the vehicle is on an incline of 5% or more after the brake is released by the driver. This feature calculates whether to engage or not by calculating the vehicle’s yaw and pitch.

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