Harsh Engagement into Reverse Gear in Cold Ambient Temperature (Reprogram PCM)

Some owners may comment on a harsh engagement during the shift from park or neutral into reverse. The condition may be most apparent if the customer shifts to reverse, then drive and then reverse a second time. The shift will be harsh on the second shift to reverse. This is also a good way for the technician to verify the concern. The concern is usually more noticeable in colder weather.

While shifting out of reverse into park or neutral, the reverse band may release before the pressure switch detects the shift out of reverse, causing the controller to think the transmission is slipping and requires additional steady state adaptive line pressure. High steady state adaptive pressure then causes a harsh shift into reverse on the subsequent shift into reverse.

If the vehicle is a 2000 Buick LeSabre or Pontiac Bonneville, verify the vehicle was built with a 67 litre (17.5 gallon) fuel tank. This can be accomplished by inspecting the fuel tank. The 67 litre (17.5 gallon) tanks have an orange and blue bar code label and the words "67 litre" stamped on the tank. Please refer to Corporate Bulletin Number 99-06-04-042 if additional information on the 67 litre (17.5 gallon) tank is required.

It is very important that the technician reproduce the concern and note the pressure control solenoid (PCS) commanded amperage during the event. If the commanded amperage is 0.1 amp (maximum line pressure), a service calibration has been released to correct this condition, as shown in the table below. If the commanded amperage is something other than 0.1 amp, the calibrations below WILL NOT address the concern. If this is the case, the technician should follow normal diagnostics and/or refer to Corporate Bulletin Number 00-07-30-002.

The calibrations listed are electronic calibrations and are NOT available from GMSPO. Program the PCM with calibrations found on TIS 2000 version 11 for 2001 or later.

For vehicles repaired under warranty, use: