Road Test and Diagnosis

To diagnosis this condition perform the following procedure:

Road Test

NOTE:
Road test should only be performed when traffic and road conditions permit. Observe all traffic safety regulations.

1. Start vehicle.

2. Enter diagnostics and select PCM parameter PD76 "transaxle gear ratio". Shift solenoid "A" is the "OFF" light for Eldorados, Sevilles, and Allantes; and shift solenoid "B" is the "ECON" light for Allantes and "DEFOG" (word not symbol) for Eldorados and Sevilles. When the solenoids are energized, the indicators light up and turn off when the solenoids are de-energized.

3. Move gear selector into D4 (overdrive range) and accelerate to 40 mph (accelerate under light throttle (DO NOT SNAP THROTTLE OPEN). Verify vehicle is in fourth gear by checking solenoid state on Electronic Climate Control display. (Solenoid "A" energized, solenoid "B" energized.)

4. Remove foot from accelerator pedal completely (zero throttle).

5. Now depress accelerator pedal (with medium speed) to approximately 30 percent of accelerator pedal travel (DO NOT SNAP IT OPEN). During the same motion accelerate (with fast speed) to "Wide Open Throttle (WOT) to force a 3-2 downshift. Throttle movement from zero throttle to WOT must be a continuous movement.

6. Observe solenoid state. When the 3-2 shift is completed, both the "OFF" and "ECON" or "DEFOG" lights on the Electronic Climate Control display should be off and PD76 should show 1.63. If the 2-3 valve sticks, the "OFF" and "ECON" or "DEFOG" lights will still go out (light off) but the ratio will be 1.00. This indicates the PCM commanded the transaxle into second gear but stayed in third gear due to a stuck 2-3 shift valve.

If the above procedure indicates that the 2-3 shift valve is sticking, the channel plate/control valve and housing assembly (903) must be replaced.

NOTE:
The terms of limited on-vehicle service as outlined in DSIB 92-I-45 under "General Guidelines" will be temporarily lifted for this condition. All other concerns related to the 4T80-E transaxle must be treated as in the past.