Bind Or Shudder On Turns (Crow Hop) - keywords auto AWD chatter vibration

This PI is being superseded to add models. Please discard PIP3928.

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

Bind/shudder (crow hop) on turns or feels like vehicle is stuck in 4 wheel drive. This concern can effect Buick Rainier Oldsmobile Bravada and Saab 9-7X or Chevrolet Trailblazer and GMC Envoy when in auto 4x4 mode.

For the 2002-2003 Bravada or the Envoy and Trailblazer (in auto mode only) please reference the latest version of tsb 02-04-21-008. If the tsb has already been performed or the vehicle falls after the tsb use the below diagnostics to isolate an electrical or mechanical concern.

1. Disconnect the encoder motor electrical connector. If the condition is gone, then proceed to step 2. If the condition is unchanged, then skip to step 4.
2. Reconnect the encoder motor connector and swap the wheels and tires from an identically built vehicle that does not exhibit the concern and re-evaluate the condition.
3. If disconnecting the encoder motor connector corrects the condition and swapping tires from another identically built vehicle does not improve the concern, snap shot the TCCM data and monitor the prop shaft speed sensors for spikes or dropping out.
4. For Bravada Rainier and 9-7X remove the encoder motor and evaluate if the concern is gone replace the encoder motor.

For the Trailblazer and Envoy remove the encoder motor and with the tech 2 in powertrain, select "Special Functions", next select "ATC Output Controls", next select "Engage Front Axle". From this screen lock the front axle and evaluate. If the concern is gone replace the encoder motor.

5. If none of the above change the condition, remove the front prop shaft and evaluate. If the concern is gone suspect a possible internal transfer case concern. If the concern is still present with the prop shaft removed suspect either a locking differential or steering related concern.

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.