Service Engine Soon Indicator Illuminated, Transmission Slips, Engine Flare, Delayed 2-3 Shift, Shifts Missing, No Shift, DTCs P0730, P0756, P0757 (Replace Accumulator Assembly/Service Transmission)

Some customers may comment that the Service Engine Soon Indicator is illuminated, the transmission slips, the 2-3 shift takes too long, or the transmission does not shift properly.

The condition may be due to an improper finish to the bore of the 2-3 accumulator housing, causing damage to the seals.

Important: Verify the vehicle build date in GMVIS. If the vehicle build date is between February 1, 2002 and April 10, 2002, proceed with this bulletin. If not within the build date, refer to SI for diagnostic procedures.

1. Road test the vehicle with the transmission fluid and engine coolant temperature stabilized at normal operating temperature. Confirm with the Tech 2® that there is a delayed 2-3 shift (greater than 0.45 seconds), or no 3rd gear operation.

Important:  INSPECTION OF A TRANSMISSION FOR EVIDENCE OF CLUTCH MATERIAL OR FINE METAL DEBRIS IN THE PAN DOES NOT A DIAGNOSIS MAKE. The transmission will have non-magnetic metal in the sediment in the transmission pan. The manufacturing/machining process of the transmission case creates a very fine aluminum dust, which when combined with the cooling/lubricating fluid turns to a paste. Even though attempts are made to remove this completely, some will ultimately be missed and will end up in the transmission fluid reservoir (pan). This paste will always remain in the pan. It can not be picked up and pulled through the filter and affect the operation of the transmission.

2. Remove the transmission pan and inspect the fluid.

•	If the fluid is in good condition, go to step 3.

•	If the fluid is burned, go to step 6.

•	If there is metallic debris attached to the magnet in the pan, go to step 6.

3. If the fluid is in good condition, remove the accumulator housing assembly and discard the assembly. Refer to SI Document ID #749332 for the procedure to remove. Assemble the new 3/4 accumulator assembly and reinstall the components.

•	3rd and 4th clutch accumulator housing is P/N 8684220.

•	3rd clutch accumulator piston seal is P/N 8661647.

•	3rd clutch accumulator piston is P/N 8683088.

•	3rd clutch accumulator piston inner seal is P/N 8661639.

4. After completing the repair, properly fill the transmission with DEXRON III® Transmission fluid.
5. Continue with Step 10.
6. If the fluid is burned or metallic debris is found attached to the magnet in the pan, the transmission will need to be removed and serviced internally.

Important:     •  All of the transmission internal components need to be removed from the transmission case assembly. The transmission case needs to be cleaned thoroughly before reassembly.    •  When reassembling the transmission, it is imperative that the original accumulator housing assembly is discarded and a new assembly is installed.

•	For transmission removal and installation procedures, refer to SI Document ID #758291.

•	For the transmission overhaul procedure, refer to SI Document ID #658951.

7. Inspect the Direct Clutch and Forward Clutch assemblies. Replace them as required during the reassembly process.
8. Before reinstalling the transmission in the vehicle, use the new Transflow Transmission Cooling System Service Tool J 45096 to flush and flow test the transmission cooling system.
9. Reinstall the transmission and properly fill with DEXRON III® Transmission fluid.
10. Road test the vehicle, performing multiple 2-3 and 3-4 upshifts from a cold start. Confirm with the Tech 2® that 3rd gear is present, and that 2-3 shift times do not exceed 0.40 seconds.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use:

Important: The recondition transmission add time is not applicable for this repair. All of the transmission clutch packs, seals and bushings have not been replaced.