Unwanted Stability Activation At Slow Speeds - keywords ABS brake gear lamp light pedal position rack stability steer steering VSES

This PI is being updated to include 2007 model years and to add keywords. Please discard PIT3914A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Unwanted stability activation at slow speeds, typically 15mph and while turning the steering wheel left or right. This may be the result of the incorrect steering gear installed in the vehicle. This PI only applies to short wheel base vehicles. Below are three ways to help identify the correct gear is installed in the vehicle.

Below, steps 1 and 2 are preliminary checks to help give the technician a guide to see if the correct steering gear is installed in the vehicle. These steps may help prevent having to locate the part number on the steering gear. However, if steps 1 and 2 lead to the direction of the incorrect steering gear in the vehicle, it is necessary to follow step 3. DO NOT replace the steering gear unless step 3 is conclusive.

1. If suspected that the wrong steering gear is installed in a vehicle, below is the approximate amount of turns from center that the steering wheel will travel to the left or right when rotated. This is just a guide. If in question, compare rotations to a like vehicle.

•	Trailblazer SS - Approximate steering wheel rotation is 1 1/2 turns from center in each direction.

•	Buick Rainier, Chevrolet Trailblazer (short wheel base), GMC Envoy (short wheel base) - Approximate steering wheel rotation is 2 turns from center in each direction.

•	Saab 97x - Approximate steering wheel rotation is 1 3/4 turns from center in each direction.

2. If the above information is not conclusive, it will be necessary to upgrade the software in the EBCM/VSES module that will allow the steering wheel position data to be viewed. To obtain additional diagnostic data for the Steering Wheel Position Sensor, reprogram the EBCM/VSES with an updated calibration using TIS-2-WEB. Select the calibration titled...

"New software with diagnostic enhancements for DTC C0455 and changes that eliminate the need to replace the EBCM when the Yaw Rate sensor is replaced."

Once the EBCM/VSES has been reprogrammed with the new calibration, the Tech 2 will now be able to access addition stability data related to the C0455 DTC and Steering Wheel Position Sensor. This data will include Steering Wheel Position Degrees, Analog Steering Wheel Position Voltage, Digital SWPS Phase A and Digital SWPS Phase B. To access this additional data in the Tech 2, build the vehicle as a 2007 model year in the Tech 2. If the Tech 2 is built as a 2006 model year, the additional Tech 2 data will not be available. Use the Tech 2 path below to obtain this additional Tech 2 data...

2007 / Light Duty Truck, MPV, Incomplete / Select Product Make (Chevrolet, GMC Buick or Saab) / Select Line (S or T) / Select Product Series (Rainier, Trailblazer, Envoy or 97x) / Chassis / Electronic Brake Control Module / Data Display / Select (ABS/TCS/VSES)

Now that the software in the EBCM/VSES module has been updated and the Tech 2 path above has been followed, Steering Wheel Position data will now be available to view. While the vehicle is on flat level ground, rotate the steering full left and full right while monitoring the steering wheel rotation in degrees. Document max degrees of rotation in both directions. The rotation of the steering on the Buick Rainier, Chevrolet Trailblazer (short wheel base), GMC Envoy (short wheel base) and Saab 97x approximately 620-700 degrees of rotation per the Tech2. The Trailblazer SS has approximately 550-600 degrees of rotation per the Tech2.

3. If step 1 and 2 above lead to believe the wrong steering gear is installed in the vehicle, locate the part number or production number on the steering gear that is in the troubled vehicle and confirm its applications with your parts department. If the vehicle is found to have the incorrect steering gear installed, replace the steering gear with current SPO stock to fit the application of the troubled vehicle.
4. Finally, if the incorrect steering gear is installed in the vehicle after following step 3, submit a product report following Service Bulletin 02-00-89-002D.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.