Here is the solution for Allison 3000 & 4000 Gen5 Transmission P0602 trouble code TCM not programmed error.
Lock in Neutral
This test verifies VEPS calibration within TCM is valid.
ACTION TAKEN WHEN THE DTC SETS:
- The CHECK TRANS light Iluminates.
- DTC is stored in the TCM history.
- The TCM inhibits shifts to range.
CONDITIONS FOR CLEARING THE DTC:
TCM must be recalibrated.
Indication of invalid VEPS calibration include:
1 Not able to connect to TCM with the diagnostic tool.
2 Cat-eyes in shift selector windows.
3 Blank selector windows occurs after pressing any selector button.
4 Check that the TCM is getting battery power, battery grounds, and ignition sense signal.
Review applicable information in the OEM Technician’s Library, CONTROL SYSTEM AND TRANSMISSION SPECIFICATIONS. GENERAL TROUBLESHOOTING OF PERFORMANCE COMPL AINTS- SHIFT SELECTOR ISSUES, and other related information.