Automatic Transmission 4-3 Shift Malfunction or 4-3 Harsh Downshift, Diagnostic Trouble Code (DTC) P1884 Set (Reprogram Transmission Control Module (TCM))

This bulletin is being revised to add DTC information to the title line. Please discard Corporate Bulletin Number 05-07-30-020 (Section 07 - Transmission/Transaxle).

Some customers may comment on the Malfunction Indicator Lamp (MIL) being illuminated or a 4-3 harsh downshift.

Technicians may find DTC P1884 (4-3 gear shift malfunction) set.

Reprogram the TCM with the modified TCM calibration that has been released to correct both the DTC and the 4-3 harsh downshift. Modifications to the calibration are as follows:

Important: The TCM will store a P0703 every time the TCM is energized. Once the TCM sees the brake switch transition from "Released" to "Applied," with the ignition switch On, then the P0703 will be cleared. If the Scan Tool is displaying the P0703 DTC, ensure that you press and release the brake before using the following diagnostic procedure. Only use the diagnostic procedure if the P0703 DTC is not cleared after initially pressing and releasing the brake pedal.

Service Procedure

1. Reprogram the TCM with service software and calibration that is included in TIS data version 8.00 broadcast to dealers via GM Access on August 7, 2005 and on TIS 2000 CD-ROM version 8.0 available August 2005. Refer to SI Document ID 1672261.
2. Check any Diagnostic Trouble Code in the TCM and ECM and then clear any stored DTCs.
3. Use a scan tool to reset the TCM Adaptation Value.

Important: Do not attempt to order the software or calibration numbers from GMSPO. The software and calibration numbers are programmed into the TCM via a Techline tool device.

The service software and calibration is included in TIS data version 8.00 broadcast to dealers via GM Access on August 7, 2005 and on TIS 2000 CD-ROM version 8.0 available August 2005.

For vehicles repaired under warranty use: