| Subject: | DTC P2723, Won't Shift Out of 1st Gear, Slips |
| Models: | 2008 Cadillac Escalade, Escalade ESV, Escalade EXT, STS-V, XLR-V |
| 2008 Chevrolet Corvette, Silverado, Suburban |
| 2008 GMC Sierra, Sierra Denali, Yukon, Yukon Denali, Yukon Denali XL |
| Equipped with 6L80 or 6L90 (RPO MYC or MYD) Automatic Transmission |
| Vehicles built in February, 2008 (Use GMVIS to verify build date) |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may comment that the transmission slips or won't shift out of 1st gear, DTC P2723 will be found in the TCM as an active or history code.
Recommendation/Instructions:
Important: This only applies to vehicles built in February, 2008 (Use GMVIS to verify build date)
- Record Freeze Frame / Failure Data for all DTCs. This can be done electronically with the Tech 2 by capturing the data or by manually writing down the parameters. This data may be requested by TAC if further assistance is needed.
- Check and note the transmission fluid level and condition. If the level is high or low it should be corrected and the vehicle road tested under the conditions outlined in SI for DTC P2723 to set and verify that the condition is no longer present.
- A: If the freeze frame data shows the Output Speed Sensor (OSS) reading to be zero when the DTC P2723 was set, the condition is likely caused by the OSS and or the Control Solenoid Valve and Transmission Control Module Assembly. Diagnose the OSS
and Control Solenoid Valve and Transmission Control Module Assembly, Replace as necessary and test drive to verify condition is corrected.
B: If condition is still present and DTC P2723 and P0878 are found together as history or active DTCs the condition
is likely caused by the Control Solenoid Valve and Transmission Control Module Assembly. Follow published diagnosis for DTC's and if leads to a Control Solenoid Valve and Transmission Control Module Assembly replace and test drive vehicle to verify condition
is corrected.
- Clear all DTCs and drive the vehicle to verify the condition. If the condition can be duplicated disassemble the transmission to inspect the 1-2-3-4 clutch piston (414 in eSI Document 1537806) for a possible crack (see illustration below). Also inspect
all 1-2-3-4 related piston seals and the 1-2-3-4 and 3-5-R fluid seal rings (230 in eSI Document 1698360).
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.
