| Subject: | TCC Engagement in 1st, 2nd or Reverse |
| Models: | 2004-2007 Buick Rainier |
| 2002-2006 Cadillac Escalade, ESV, EXT |
| 2001-2005 Chevrolet Astro |
| 2002-2007 Chevrolet Avalanche |
| 2001-2005 Chevrolet Blazer |
| 2001-2002 Chevrolet Camaro |
| 2004-2007 Chevrolet Colorado |
| 2001-2005 Chevrolet Corvette |
| 2001-2007 Chevrolet Express, Silverado, Suburban, Tahoe |
| 2002-2007 Chevrolet Trailblazer |
| 2001-2007 GMC Savana, Sierra, Yukon, Yukon Denali, Yukon XL |
| 2001-2004 Oldsmobile Bravada |
| 2001-2002 Pontiac Firebird |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Vehicles equipped with 4L60E/65E/70E transmissions may experience a low power, chuggle, shudder or perceived harsh shift concern under acceleration just after pulling away from a stop. The TCC apply valve (item 224) or the TCC enable solenoid may be stuck
or lodged with debris causing premature TCC apply.
Recommendation/Instructions:
The following diagnostics may be helpful to determine if the TCC apply valve or enable solenoid is lodged or stuck.
- Does TCC apply when PWM oil ramps up; this will be at approximately 6-8 mph and may also occur in reverse. TCC slip speed will also drop when PWM oil ramps up?
- Does the TCC apply even though the TCC enable solenoid is commanded off?
- Can be condition be eliminated by commanding the TCC off with the tech 2 scan tool?
Note: Applying the brakes will not eliminate this condition. The vehicle will not stall at stop due to the PWM oil going to "0" at 6 mph or less.
Also air leak test the TCC enable solenoid for sticking or a blockage.
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.
