| Subject: | Harsh TCC Apply or Vibration in Active Fuel Management V4 Mode If Equipped With AFM |
| Models: | 2005-2006 Cadillac Escalade, Escalade ESV, Escalade EXT |
| 2005-2008 Chevrolet Avalanche, Colorado, Suburban, Tahoe, Trailblazer |
| 2005-2007 Chevrolet Silverado Classic |
| 2007-2008 Chevrolet Silverado |
| 2005-2008 GMC Canyon, Envoy, Sierra Denali, Yukon, Yukon XL |
| 2005-2007 GMC Sierra Classic |
| Equipped with 4L60E, 4L65E or 4L70E (RPO - M30, M32 or M70) Transmission |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may comment on a harsh TCC apply. Customers may also comment on a vibration when in active fuel management V4 mode if the vehicle is equipped with AFM.
The above concern may also occur in vehicles that are not equipped with active fuel management (AFM) but will only be noticed as a harsh TCC apply.
Recommendation/Instructions:
This condition may be caused by the valve body regulator apply valve (380) being stuck or forced into the apply position at all times. This valve controls the flow of line pressure into the regulated apply fluid circuit which controls TCC slip rate.
If this valve is stuck in the full apply position TCC slip will be zero whenever TCC is enabled.
Use a Tech 2 to monitor TCC slip speed. When TCC is enabled slip speed may momentarily go to zero but should increase to 20 rpm or greater and should not remain at zero. If the TCC slip speed remains at zero remove the valve body and inspect the regulator
apply valve (380) for freedom of movement in it's bore. When installed this valve should have free movement in the bore and should not be pre-loaded against the bore plug (381).
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.
