Vehilcles have many options in one type of ECM. So automatic recognition function is applied. The options that can be recognized are MT/AT, 2/4WD, DPF, etc). When a ECM is installed to vehicle, these options recognition are performed by the ECM automatically as checking whether ground line is grounded or opened every IG KEY ON process.

If this recognition is not fulfilled well or any error occurs during the process, engine power generation is not sufficient and glow lamp on cluster blinks.

If a system is intalled, the ECM connector is grounded.

Else is opened (no wire exists).

P1594 is set when the signal from 4WD auto recognition terminal changes during engine running. This code is due to open in terminal for 4WD option, grounded condition for 2WD option. This code is normally arises from 4WD option vehicle. Check the grounding condition of 4WD auto recognition terminal.