P287B: Shift Fork A Calibration Not Learned

What it means

The TCM has not learned the end-stop calibration for shift fork A. Engagement positions cannot be commanded with full precision until adaptation completes.

At a glance

• Usually lights the check-engine light

How it works

Shift fork A moves a transmission selector to engage its associated gear positions. The TCM needs learned end-stop positions to control that fork precisely; P287B sets when the calibration has not been learned, so fork A’s engagement positions may be imprecise.

Common causes

Most likely first.

1. Adaptation lost after battery disconnect or TCM reset
2. Shift fork replaced without learn procedure

Symptoms

• Check engine or transmission warning light on
• Harsh, delayed, or missing shifts
• Possible limp mode (locked in one gear)
• Slipping or shuddering during gear changes

How to diagnose it

1. Save freeze-frame data and check TCM live data for shift fork A’s learned status and any related transmission codes.
2. Ask whether the battery was disconnected, the TCM was reset, or shift fork A was recently replaced, as these events can erase or require calibration.
3. Inspect the accessible shift-fork actuator wiring and connectors for loose plugs, damaged insulation, or corrosion that could prevent a learn procedure.
4. Check that the transmission has no active faults or mechanical symptoms that would prevent calibration from completing.
5. If the underlying conditions are sound, perform the manufacturer’s shift fork A learn procedure with a capable scan tool and confirm the learned status afterward.

Common fixes

• Complete the manufacturer’s shift fork A calibration procedure.
• Repair a loose or damaged connector or wiring to the shift-fork actuator.
• Address any active transmission fault that prevents the calibration from completing.
• Inspect or repair shift fork A and its actuator if the learn procedure repeatedly fails.

Can I keep driving?

If shifting is normal and there are no other warning signs, a short, cautious drive may be possible, but avoid heavy loads and hard acceleration until calibration is completed. Stop driving if gears are missing, shifts become severe, or the transmission enters limp mode.